This is just one of some 80 files about machining and metalworking and useful workshop subjects that can be read at: http://www.janellestudio.com/metal/index.html ------------------------------------------------------------------ Here are users' tips about a metal lathe's thread dial attachment and the half nuts aka split nuts. For the new metal lathe owner, one of the greatest mysteries to be solved is how to use the thread dial attachment (assuming the lathe has one), along with the half-nuts (also called split nuts) that connect the lathe carriage to the lead screw so that it will move under lathe power. Every user will eventually have to replace, rebuild, or make half-nuts when they become worn. The file here called Threading (Lathe or Otherwise) also has some tips on thread dial use. If you got to this file directly from my HOME PAGE, return there by using your browser's back button. BUT if you came to this file as the result of a web search engine, see many additional files on my home page Machining and Metalworking at Home http://www.janellestudio.com/metal/index.html SAFETY WARNING BEWARE: DO NOT ASSUME that any subject matter or procedure or process is safe or correct or appropriate just because it was mentioned in a news/user group or was included in these files or on this site or on any other web site or was published in a magazine or book or video. Working with metals and machinery and chemicals and electrical equipment is inherently dangerous. Wear safety devices and clothing as appropriate. Remove watches, rings, and jewellery -- and secure or remove loose clothing -- before operating any machine. Read, understand and follow the latest operating procedures and safety instructions provided by the manufacturer of your machine or tool or product. 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(c) Copyright 2003 - 2016 Machining and Metalworking at Home The form of the collected work in this text file (including editing, additions, and notes) is copyrighted and this file is not to be reproduced by any means, including electronic, without written permission except for strictly personal use. ========================================================================== Date: Mon, 12 Feb 2001 20:21:49 -0000 From: WThanelx~xxaol.com Subject: Thread Counting Dial Gear M6-64 or M6-64A? I have recently restored (assembled from parts) an Atlas 6 inch 618 lathe and decided to try turning some threads. Upon trying to use the thread counting dial I noticed it will not stay engaged with the leadscrew. When the half nuts are disengaged I can push the dial gear against the leadscrew and tighten down the positioning bolt. The dial will then rotate as the carriage is moved. As soon as I engage the leadscrew the gear disengages and the dial does not turn. I see in the Atlas 618 parts list that two dial gears are listed, the m6-64 and the m6-64A, hmmm. I have assembled this lathe from new and used parts. The leadscrew and gear appear to be in exe condition. I don't think the thread counting dial came with the leadscrew so its possible I have the wrong gear. Only one lead screw number is listed in the Atlas parts list. Has anyone had this problem? What is the difference between the M6-64 and the M6-64A gear? Thanks Bill T. ------- Date: Mon, 12 Feb 2001 15:36:46 -0500 From: Jude Miller Subject: Re: Thread Counting Dial Gear M6-64 or M6-64A? I have a 6" A/C with a 32 tooth dial gear. Some of the 6" Atlas lathes have a 16 tooth dial gear. Perhaps that is the difference? You could call Clausing and ask. The 16 tooth gear saves a few seconds each time you start another pass, but the 32 tooth gear allows you to cut 1/2 threads, e.g. 11 1/2 tpi, a pipe thread. Best, Jude Miller ------- Date: Mon, 12 Feb 2001 16:01:00 EST From: BACSTGx~xxaol.com Subject: Re: Thread Counting Dial Gear M6-64 or M6-64A? There are two possibilities here. When you engage the half nuts the dial should not rotate. It should stay where it was when you engaged them. The carrage moves at the same rate as the lead screw is turning so the gear on the dial is just following the grove in the leadscrew. The other possibility if this is not the problem is that when the leadscrew is engaged it is slightly warping the carriage and causing the gear to pull off of the leadscrew. To fix this you need to shim the distance between the halfnut and the carrage. My old one before I sold it had two thin washers to take care of this problem. Hope this helps. Keith ------- Date: Wed, 14 Feb 2001 00:06:29 EST From: catboat15x~xxaol.com Subject: Re: engaging carriage [atlas_craftsman] In a message dated 2/13/01, lnicex~xxattglobal.net writes: > Sometimes when I engage it it locks onto the leadscrew > smoothly and sometimes it takes several tries before it engages. You are doing nothing wrong. The half nuts will not engage if they are trying to close on top of the thread, when the lead screw turns so the half nuts are on the thread properly they will engage. I usually put light pressure on the lever to engage the half nuts and when they and the lead screw are in "sync" they just drop in. You are correct in not forcing anything here. John Meacham High Desert of California, Palmdale, Littlerock. ------- Date: Tue, 13 Feb 2001 23:35:19 -0600 From: "J Tiers" Subject: Re: engaging carriage Perhaps you are not observing the thread dial (if you have one) correctly, or it is out of correct alignment. You should ONLY be able to engage when a line on the dial is RIGHT on the index mark on the dial housing. The further off the mark it will engage, the more wear and consequent slop your nuts and screw have. In some cases it will engage halfway between marks, that is also OK. If the mark is off the index when it goes in, shim the dial where it fits against the carriage, or turn the gear on the dial shaft to bring it back in. If no dial, then it still engages, but you cannot easily see where! Jerry ------- Date: Wed, 14 Feb 2001 00:54:40 -0600 From: Jon Elson Subject: Re: engaging carriage You probably have wear on the half-nuts. Also, there is a 'bracket' that holds the half-nuts in proper position, and it can get loose. Check to make sure the entire half-nut mechanism is clean, well lubricated, and that the half-nut pieces themselves are held securely in the little vertical tracks that guide them. Keep the leadscrew clean and well lubed, too. I think that using the threading dial to select the proper moment to attempt engagement is a big help. If you are trying to do it by feel, you may be causing excessive wear this way. Jon ------- Date: Mon, 12 Feb 2001 22:37:11 -0000 From: WThanelx~xxaol.com Subject: Thread Counting Dial Gear M6-64 or M6-64A Solved ! My original question has been solved. Although I still don't know the difference between a M6-64 and a M6-64A I guess I really don't need to. Thanks to some fellow memebers I now know thread counting dial is working correctly. Having never used one before I was unfamiliar with its operation principals. Thanks to all that replied for the info. Bill T. ------- From: Sent: Tuesday, February 13, 2001 10:00 PM Subject: [atlas_craftsman] engaging carriage > Got a question for you. I have a 10" Atlas that seems to have very > little wear on it and except for an annoying problem with engaging the > carriage seems to performs well. The problem I have (at least I think I > have) is an erratic engagement of the half nut to start the carriage > (horiz) to move. Sometimes when I engage it it locks onto the leadscrew > smoothly and sometimes it takes several tries before it engages. What am > I doing wrong here? I don't want to force it and break something. Thanks > for any suggestions. Iceman I saw your post on leadscrew engagement. Firts make sure thread dial is turning freely and the little gear is engaging the leadscrew consistently. Sometimes the gear may not be swung far enough in to totally engage the leadscrew consistently. Take a peek at the half-nuts in the carriage. They may be worn and need replacement. Make sure no chips or dirt have accumulated to slow the action of the half nut lever. Flush out with some sort of solvent and put in clean lube. Look at the leadscrew itself for worn down threads. You may need a replacement. If wear or dirt or chips are not the problem, you may be closing the half-nut lever too soon or too late. The little index marks on thread dial and dial body are approximate. As the manual says, different marks for different threads, odd or even number. Make sure the right marks are used for the thread you want to cut. You have to get a "feel" for when to close the lever and how fast to close it. Leadscrew may turn faster or slower depending on thread being cut. You have to go faster or slower in closing the half-nut lever. Sometimes you have to close the half-nut lever just before indicator marks meet. I hope this helps. J. Sprott Kansas City, MO ------- Date: Wed, 14 Feb 2001 09:01:25 -0700 From: "Maxwell Sandford" Subject: Re: engaging carriage > The problem I have (at least I think I > have) is an erratic engagement of the half nut to start the carriage > (horiz) to move. Sometimes when I engage it it locks onto the leadscrew > smoothly and sometimes it takes several tries before it engages. Now that this thread is going well, has anybody started to design a synchronizer ring for Atlas lathes? Like any transmission, you can only powershift when the nut thread is lined up with the leadscrew. My 6" behaves exactly this way too, owing of course to the simple design of the half-nut engaging mechanism. It engages smoothly when the teeth are in position with the leadscrew, so there is no substitute for operator training. ------- Date: Wed, 14 Feb 2001 12:14:30 -0500 From: Jude Miller Subject: Re: engaging carriage > I guess I need to be trained. Everyone answered this question as if he > was threading. What if he was not threading but only turning and did > not have the thread dial engaged? Jerry Halcomb You can still only engage the half nuts when the threading dial is at one of the marks or half way between. Just use the carriage handwheel to move the carriage until the threading dial lines up with the mark. Otherwise, use very gentle pressure on the half nut lever while you move the carriage slightly. You should be able to feel when the half nut will engage. Best, Jude Miller ------- Date: Wed, 14 Feb 2001 09:24:13 -0800 From: "Bob May" Subject: Re: engaging carriage When you engage a halfnut, the square threading keeps it up until you have an alignment. Push gently and all of a sudden, it will drop in. If you engage the thread dial, you will quickly see which positions that it will engage in. I, probably like a lot of us, keep the thread dial engaged and watch it for when it indicates an alignment and that's where I push down firmly. Any other place just frustrates you as you have already found out. Pushing and releasing can also mean that you miss the thread for several threads as you just jump over the alignment point! Bob May My new web space address is http://webu.wigloo.com/bobmay/ or http://nav.to/bobmay ------- Date: Wed, 14 Feb 2001 16:15:20 -0600 From: Jon Elson Subject: Re: engaging carriage Adam wrote: > At 10:52 AM 02/14/2001 -0600, you wrote: > >Everyone answered this question as if he was > >threading. What if he was not threading but only turning and > >did not havethe thread dial engaged? Jerry > Basically the same thing, except you don't need to pay attention > to the marks on the thread dial. One of the first replies I saw > mentioned closing the half nuts with a certain kind of 'touch', > not forcing but more like easing it in. The half nuts will still > only engage when the threads are lined up with the lead screw, > that holds no matter what operation you are running... Well, after there is some wear in the nuts, rounding off the corners, etc. you CAN engage the nuts on the side of the thread. In other words, you can get the nut only partially engaged over the leadscrew. When threading, this causes a big mess, as the tool will not be in the right alignment to the thread you are cutting. I suspect this partial alignment also increases wear on the nuts. So, I am very careful to use the threading dial and a very light touch to get the nuts engaged. Jon ------- Date: Sat, 25 May 2002 21:41:55 -0500 From: "jerdal" Subject: Re: split nut problem > Hello,My 109 split nut will not stay engaged when cutting without > having to hold it down.After examining the problem I discovered part > of the bottom half was broken off.Is there any wat this can be > repaired.Otherwise the lathe operates perfectly.Any Ideas? Bill There is a detent that is supposed to hold it in position. Evidently this is the part broken off. You could probably braze on a part to replace it, and drill for the detent parts. Finding new ones or replacement is an Ebay issue, as NOS parts are probably not happening anymore. Or, one of the folks here who has a machine to part out may have something. One of the articles on the machine in HSM / MW had an "always engaged" nut description. This might not be too bad, since the leadscrew is used for ALL carriage movement on these machines. Jerry ------- Date: Sun, 26 May 2002 03:05:25 -0000 From: "bill_collins14" Subject: Re: split nut problem Jerry, The detent is fine. It is part of the bottom half of the nut part itself that has a piece broke off. I took the carriage off and re- examined the piece and found that part of the bottom half of the threaded section was missing. If I can't find a replacement piece then maybe I can fabricate a new piece for it. I had to make one similar for an old Shepard lathe I used to own and it was much older than the 109. As for the detent it is fine, in fact when I first got the lathe I had to replace the ball bearing that presses against the indent on the split nut that's supposed to hold it in position. I'm sure I will figure something out. Thanks Bill ------- Date: Sat, 25 May 2002 22:14:00 -0500 From: "Mario L Vitale" Subject: Re: split nut problem Bill, There was an article about a year ago in Home Shop Machinist / Projects in Metal mag (and it was discussed by this group) on how to repair the half nut. If you are interested and can't find the article, let me know and I'll see if I can dig it out for you. It may take me a day or two. My filing system is great...it's my retrieval system that stinks!!!! Mario ------- Date: Sat, 25 May 2002 22:43:54 -0500 From: "Mario L Vitale" Subject: Re: Re: split nut problem Bill, It looks like we are on the same schedule! I found the article (Machinist's Workshop [used to be Projects in Metal] magazine, Dec 2001/ Jan 2002 Vol 14 #6 page 27.) It is discussing repairing the half nuts on a SB 10K lathe but the process would work for any lathe. The basic approach is to build a fixture that holds the two nut halves in the same relative position that they are held in the apron, build up the worn surfaces with braze material, and then tap the threads to match the lead screw thread. If you can't find the magazine let me know and I can try to scan the article for you. Mario ------- Date: Sun, 26 May 2002 03:57:26 -0000 From: "bill_collins14" Subject: Re: split nut problem Mario, with the AA 109 both halves of the split nut are cast onto the same piece that engages on the lead screw. I may have to go with something like on the Gingery lathe. Or when I fixed the one on the old Shepard lathe I cut a nut in half that matched the lead screw and welded them onto a piece of CRS plate then used a hacksaw to remove the waste and finished the shaping on a bench grinder then drilled the holes needed to mount it to the apron. Gotta put my old brain to use. Thanks a bunch. Bill ------- Date: Fri, 08 Nov 2002 09:04:14 -0800 From: Rick Kruger Subject: Restoring worn half nuts with a bronze sleeve Not wanting to wait for Brett to figure out how to get into Yahoo groups, I've uploaded his description and photos of how he restored badly worn SB9 Model A half nuts using a bronze sleeve. While this was done on a SB lathe, clearly it has application to any lathe. Its a mystery how these nuts were worn out so completely, but there was almost nothing left of the threads. Since it is a Model A, power feed of carriage and crossfeed were thru the leadscrew keyway, not the half nuts. Half nuts were only needed for threading. The lathe was in a high school shop for a long time. A short description file and two photos have been uploaded to the FILES area. http://groups.yahoo.com/group/atlas_craftsman/files/RestoredHalfNuts/ Brett will not see discussion posted to the Atlas group, but I can relay. If you want to ask Brett questions offline, please email him at: efficientvelox~xxaol.com Rick K. Portland, OR ------- Date: Thu, 2 Jan 2003 21:42:21 EST From: LouD31M066x~xxaol.com Subject: Re: 618 Atlas metal lathe [HALF-NUT PROBLEM] Check with Clausing Atlas...as of last year they were $15.72 for pair of half nuts new. Complete assembly $49.42 ...now there you might want to shop a little. I have quoted from 05/14/01 price list for my 101.21400 six inch lathe. I assume the parts are the same and price has not gone up too much since. Sometimes not the case so check first. Are you sure half nuts are unusable? Reason I ask is my well worn lathe had lead screw coated with gummed up oil and crud and half nuts were full of shavings and gummed up oil...after lead screw was cleaned up and shavings picked out of half nuts there was nothing wrong with either! Anytime you avoid buying things you don't need you have more money left to spend on the things you do need...don't even think about asking how I learned this! Louis ------- Date: Thu, 2 Jan 2003 22:13:21 EST From: LouD31M066x~xxaol.com Subject: Re: 618 Atlas metal lathe Have read your message again. I went off half cocked. Let's start over... Is lead screw coated with a varnish that fills thread? I used power wire brush to remove...if had to do it over I would use a bronze or brass instead of steel wire wheel. Are all the parts present and accounted for? Is wear or breakage obvious? Do you have owners manual or can you access from group web site? The parts involved are sacrificial items made of easily broken material that will give way in case something has to give. Except for handle they are reasonable and available (as of last year) M6 13a guide $4.33 M6 12A half nuts(pair) $15.76 M6 38 cam $2.79 M6 29 lever is a pricy $38.23 but A) not likely the problem and B) a clever native craftsman can make a substitute. If new parts are available reasonably why bother with used in this application? At least that's how I see it. (2nd time anyway) Final thought..is spring and ball assembly present and free of gunk and crud? It is not clear from drawing where they fit but something has to provide positive position of in or out on half nut. Do not have carriage available just now...out being ground. Louis ------- Date: Fri, 3 Jan 2003 03:11:15 -0500 From: "mertbaker" Subject: Re: 618 Atlas metal lathe You can get the "Loctite Thread Restorer" kit at an automotive store. Follow the directions exactly. Mert ------- Date: Fri, 03 Jan 2003 18:03:34 -0000 From: "speedphoto300 " Subject: Re: 618 Atlas metal lathe Dennis: If you do buy the half nuts, check first to see if your old ones are .5 or .75 inches wide, the ones available from Clausing are the more recent wider ones. If yours are the narrow ones you either need to get the M6-13A guide or widen the slot in your old one. Joe ------- Date: Mon, 10 Feb 2003 05:10:27 -0000 From: "don_kinzer " Subject: Re: Cutting a gear on the shaper [Metal_Shapers group] [A TALK ABOUT THE THREAD DIAL HERE] jrw wrote: > Don: The part I do not understand is the comment about > needing five gears for the threading dial. The way that the thread cutting gearing works out on this lathe (which, again, has a metric leadscrew) a 16T thread dial gear will work for .3, .4, .5, .6, .75, .8, 1.0, 1.2, 1.5, 2.0, 3.0, 4.0, 6.0, 8.0 and 12.0 mm pitch threads. For all but the 8.0mm pitch, the halfnut can be engaged on any of 8 marks on the dial. For the 8mm pitch, only the 4 numbered marks may be used. For other thread pitches, you need different thread dial gears. An 18T gear covers some of the same pitches (although the halfnut can only be engaged on the "1" mark or, in some cases, the "1" and "3") but also adds .45, .90, 4.5, and 9.0mm pitch. A 20T gear adds 1.25, 2.5, 5.0 and 10mm pitch and the halfnut can be engaged on any of 4 numbered marks. A 21T gear adds .35, .7, 1.4, 1.75, 3.5 and 7.0mm pitch but the halfnut may only be engaged on the "1" mark. Lastly, a 22T gear adds 1.1, 5.5 and 11mm pitch, halfnut to be engaged on "1" or "3". The manual that I have for the lathe, unfortunately, only covers the Imperial (inch) leadscrew. I had to work all of this out using a spreadsheet. The advantage of this process is that I now understand how the thread dial works. I could probably get by without the 18T and 22T gears but while I have everything set up I might as well make them. Don Kinzer Portland, OR ------- Date: Wed, 19 Feb 2003 12:00:30 -0500 From: "John Glowacki" Subject: Mitre Gear/Half Nut [atlas_craftsman] After falling on a small patch of ice in my Wisconsin driveway 12/20/02, I was finally able to hobble to my shop last night. I just sat on my stool and gazed at my various un-finished projects. It was great just to be there. I've had it with taking life for granted! I just called Clausing for parts prices for my A/C 101.07403. The mitre gear (P/N 10F-82A) that slides over the lead screw and drives the cross feed power is almost a hundred bucks!! Mine is missing the key protrusion that interlocks with the slot in the lead screw. For a hundred bucks, I think I can tinker for a while and try and fix it. I will bore out the gear and press in a brass sleeve with an internal key affixed to the inside. Or I might just try to affix an internal key to the inside of the gear bore. Also I priced the half nut P/N 10F-12 at about $28. Someone was asking about half nuts for a six inch Craftsman. Is that the same part number? Well, I'll be back in my shop tonight. John Glowacki ------- Date: Wed, 19 Feb 2003 12:06:21 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut Glad to hear you are up and at it again....somewhat anyway. 6 inch half nut part number is M6-12A (pair) halfnuts $15.76 May 2001 price list. Difference between ordering part and a project is cost. Some parts are too inexpensive to try to make and others are too complex and difficult. Where the part is either unobtainable or easier to make than to pay for you have a project. Sometimes projects annoy and divert us from a primary task sometimes they offer variety and the opportunity to enhance our skills. The question is fix, find, adapt or improvise? Have fun! Louis ------- Date: Wed, 19 Feb 2003 12:33:26 -0600 From: Jon Elson Subject: Re: Mitre Gear/Half Nut John Glowacki wrote: >I just called Clausing for parts prices for my A/C >101.07403. The mitre gear (P/N 10F-82A) that slides over >the lead screw and drives the cross feed power is almost a >hundred bucks!! Mine is missing the key protrusion that I'd go for the brass sleeve, it will be a lot stronger than any key you might be able to cobble into the gear. Remember, the original cast-inkey sheared off due to the force on it. The sleeve will support the key much better. >Also I priced the half nut P/N 10F-12 at about $28. > Someone was asking about half nuts for a six inch >Craftsman. Is that the same part number? No, the 6" has a 16-pitch leadscrew of smaller diameter. So, the half nuts are not the same. In fact, very little is compatible between the 6" and other lathes. ------- Date: Wed, 19 Feb 2003 13:52:42 -0500 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut If I do bore out the mitre gear and fabricate a brass bushing with an internal key protrusion: 1. The wall thickness would be about 1/16" on both the gear and the bushing. With the gear being about 1" in diameter and 1 1/2 or 2" long, can I hold this in a chuck (3 or four jaw) for machining? I'm thinking that the chuck jaws might crush the thin wall. 2. What diameter differential would make a good press fit? 0.002"? I could heat the gear before pressing in the bushing. Thanks for the help. John Glowacki ------- Date: Wed, 19 Feb 2003 14:26:03 -0500 From: Stan Stocker Subject: Re: Mitre Gear/Half Nut Hi John, If the bevel gear is one of the Zamac (cast stuff) ones, you might do better to go with a sliding fit and secure the sleeve with some thinned epoxy or one of the high strength bearing retaining compounds. Zamac isn't very good in tension. Cheers, Stan ------- Date: Wed, 19 Feb 2003 15:46:22 -0500 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut Stan, I don't think my gear is zamak. It sticks to a magnet. Zamak wouldn't stick to a magnet, would it? John Glowacki ------- Date: Wed, 19 Feb 2003 17:24:21 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut No...I think more due to very small scale of interest/demand. The supplying of parts for any obsolete product is more an act of generosity on part of the manufacturer than a source of profit. It takes a certain minimum amount of resources to provide parts and service whether sales are high or low and the cost must be reflected in price. In our situation we should be glad that our old machines still have many parts available new even at costs that seem high. Otherwise we would have to junk our machines for want of the proverbial horse shoe nail. It was a different story when our machines were in current production. Then parts and service were profit centers contributing to overall success of business...not so now. Louis ------- Date: Wed, 19 Feb 2003 17:37:34 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut Magnet identifies as iron or steel and rules out zamac. Be very sure you are not dealing with an insert of some sort. Atlas was very partial to zamac parts as they were cheap, serviceable and provided a wearing or weak safety link in their design. Louis ------- Date: Wed, 19 Feb 2003 17:40:15 -0500 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut Yep, I'm sure a magnet sticks to the gear teeth and the shank. It's not zamac. John Glowacki ------- Date: Wed, 19 Feb 2003 17:57:32 -0500 From: Stan Stocker Subject: Re: Mitre Gear/Half Nut Hi John; Sounds like your part isn't Zamac! Makes life nicer indeed. 2 thou sounds pretty good on a one inch diameter for the fit, given the amount of surface area even a thou would likely do fine. On small parts like this I often heat the outer part over a light bulb and put the inner piece in the deep freezer. Line it all up, don't dawdle, and tap the part home quickly. Any chance you could just broach a keyway and fit a key in the existing piece rather than go through the effort of boring out and fitting a liner that still required a key to be secured in some way? Good luck with it, Stan ------- Date: Wed, 19 Feb 2003 17:55:52 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut [Louis' msg a few minutes earlier] >> If gear is zamac (I suspect it is) it might not be up to much in way of heat or pressure so I would go with an epoxy glue and a slide on fit. You have the dollar figure of the part to bear in mind! Holding to machine might also be a place where an epoxy glue and very gentle cuts could work where other more vigorous measures would put you in deep doo doo. $0.00000002 worth. Louis << Please forgive my assumption of zamac. If gear is steel I am wondering what did it wear on to wear out internal key or keyway? If gear is steel it will likely machine or press or heat okay. If lack of a way to hold it is a problem epoxy to a flat surface you can fasten to face plate (indicated center) and make fine cuts might be one way out. My humble opinion and sometimes I have much to be humble about. Final thought...goal is to have renewed internal key and bore concentric to center of gear surface, solidly bonded together to transfer motion from leadscrew to crossfeed. Should be doable with due attention to making things concentric and close fit. Thought occurs that if outer surface is machined (and concentric to gear) you could turn and bore a piece of barstock to make a holding fixture using epoxy to grip gearshaft while boring it out then using source of heat to weaken epoxy so as to remove gearshaft from fixture. That way no chuck jaw distortion of gearshaft being held....opinion worth what you pay for it. Louis ------- Date: Wed, 19 Feb 2003 20:12:05 -0600 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut You know Louis, I'm not so sure my father didn't bore the key out of this gear. The other mating gear was missing, along with the mounting stud. I don't ever remember the power cross feed working on this lathe. And I first started playing with this lathe when I was maybe ten years old, some thirty years ago. I can't for the life of me think of a reason why dad would have bored out this key. The hole looks bored out. This could be from a lifetime of spinning on the lead screw. John Glowacki ------- Date: Wed, 19 Feb 2003 20:23:34 -0600 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut > turn and bore a piece of barstock to make a holding fixture using epoxy to grip gearshaft while boring it out then using source of heat to weaken epoxy so as to remove gearshaft from fixture. That way no chuck jaw distortion of gearshaft being held....opinion worth what you pay for it. Louis < Now you're getting the gears turning, so to speak. This might be my answer. Or even a custom collet to hold it in a chuck? John Glowacki ------- Date: Wed, 19 Feb 2003 20:17:33 -0600 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut Two things Stan, 1. I'm a bit puzzled as to how I could affix a key to the inside of the gear itself. If I make a brass sleeve, I can braze or silver solder it in. 2. The inner bore of the gear is a bit open. There might be too much play between the inner bore and the lead screw. How much play should there be? John Glowacki ------- Date: Wed, 19 Feb 2003 22:34:18 -0500 From: Stan Stocker Subject: Re: Mitre Gear/Half Nut Hi John; I'm far more familiar with South Bend, the Atlas I'm wrapping up is the first I've worked on. On South Bend lathes, the key in the worm has ears on the end, and is quite thin in the section that goes through the worm. The ears keep the key from sliding out of the worm when the leadscrew is in place. The key just about falls out when the lead screw is removed, only a light tap with a brass drift is required to free it. On the Atlas, the leadscrew runs through one of the bevel gears rather than through a worm as we all know. What I don't know is if there is enough meat at each end, or enough room for a key with ears and just a shallow slot through the gear body. Unfortunately, I have no idea what the fit is on new Atlas gears and leadscrews. I was thinking that if you had room to bush, you might have enough room to go with the key with ears approach and save some time, or to secure a key into the existing gear using lower temp silver bearing solder which flows at around 475F unlike the higher temps required for true silver or brass brazing. I don't think I'd choose to take a steel gear that is probably heat treated up to true brazing temps, although I've done it often enough on cast iron gears to replace teeth. Sorry not to have been more complete in explaining what I was thinking of, I'm just so used to SB that I often forget that Atlas did things differently in some areas. Cheers, Stan ------- Date: Wed, 19 Feb 2003 22:46:38 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut If you are missing more ie. both gear and stud I would follow ebay and ask group if anyone has the parts lying in their bone pile. The repair you are considering is doable but why bother if you still need stud 10F-17 and gear 10F-83. I do not think these are wear items so used should be okay. Another angle is to see if Boston Gear (or their competition) has gears (mitre and spur) that you can join to make 10F-83. You might have to make the whole setup if you cannot find match for 10F-82 mitre gear. Looking at prices I see you have strong incentive to "roll your own" in this situation including mounting stud 10F-17. I suppose you could even make your gears from scratch, but, I think that might be a stretch. Louis ------- Date: Wed, 19 Feb 2003 22:51:01 EST From: LouD31M066x~xxaol.com Subject: Re: Mitre Gear/Half Nut My two cents on fit...this is all "Government Work" so any thing that works is okay. If it don't work the first time it will the next. Louis ------- Date: Thu, 20 Feb 2003 08:12:57 -0500 From: "John Glowacki" Subject: Re: Mitre Gear/Half Nut A while back, I bit the bullet and bought new from clausing the stud and gear 10F-83. The stud didn't cost much and the gear was a bit more, perhaps $50++. I bought these parts thinking I would be done. When I was putting everything together, I couldn't figure out how the power went from the lead screw to the gear. You folks helped me out on that. Then I realized my built in key wasn't there. John Glowacki ------- Date: Wed, 05 Mar 2003 08:46:58 -0000 From: "Robert Weersing" Subject: Re: Help!! parts needed for a 9" [atlas_craftsman] "CRAIG THOMPSON" wrote: > I need a set of half nuts for a 9" atlas anyone got any or know > where to get them? otherwise i need to buck up and buy an acme > tap for $58 and make them myself. Please help me!!! Thanks, Craig Hello Craig Forget calling Clausing, they only carry the 10F half nuts. The only place to find them is on Ebay. you can use the half nuts from a 9" or early 10" Atlas lathe up to a "D" model with the 5/8 lead screw. The Part number is 9-12. Lots of luck Bob ------- Date: Wed, 5 Mar 2003 00:26:48 EST From: n8as1x~xxaol.com Subject: Re: Re: Help!! parts needed for a 9" snocat_trfx~xxhotmail.com writes: > I just might be making them, though i need to buy a 5/8-8 acme tap single point threading a 5/8 x8 is only more difficult than internal v threading in the necessity of grinding the tool bit.........grind it undersize,set the compound parallel to centerline,cut the thrd w/ x/slide to FULL DEPTH, take .001 to .002 cuts w/compound shaving& cleaning up sides of thrd till u get the fit...then there is lubing the l/screw & closing the releived nut on l/screw w/ JB weld... or replacing lead screw w/ piece of 3/4x8 acme rod. best wishes docn8as ------- Date: Thu, 17 Apr 2003 13:29:58 -0500 (CDT) From: dswrx~xxwebtv.net Subject: Re: Proper procedure for engaging half-nuts on 6" Bruno, The half-nuts can be engaged/disengaged with the lathe in operation or stopped. When you close them, you can feel when they match the thread on the leadscrew. In threading operations, it is almost mandatory that you engage them while the leadscrew is turning. Leo (pearland, tx) ------- Date: Thu, 17 Apr 2003 12:43:11 -0700 From: John Weight Subject: Re: Proper procedure for engaging half-nuts on 6" Hello Bruno, Yes it is perfectly safe to engage the half nuts with the lathe running. In fact the thread on the leadscrew is an Acme thread with sloping sides.....when you watch the threading dial marks coming up to the reference line you can start to engage the half nuts "very slightly" before the two marks line up, then you can feel the nuts close on the leadscrew, (which helps to ensure that the half nuts are fully engaged) If I can help you any more please do not hesitate to E-mail me .....I taught Machinist apprentices for quite a few years and always enjoyed it. Going back to the threading, you will obviously be turning the component at a slow speed, and with practice you will be able to come up to a shoulder pretty closely before disengaging. Where are you located? What are your interests? regards John W San Francisco ------- Date: Thu, 17 Apr 2003 16:05:02 -0400 From: "Rigrac" Subject: Re: Proper procedure for engaging half-nuts on 6" Bruno: Split nut can and should be engaged with machine and lead screw both running. It would be extremely difficult to cut a thread by having to stop machine to engage split nut on every pass. All parts of screw and nut are designed to be engaged when running. Ron ------- Date: Thu, 17 Apr 2003 23:06:11 -0500 From: "jerdal" Subject: Re: Proper procedure for engaging half-nuts on 6" I will disagree... sort of... with the other folks. It WILL damage the halfnuts to engage a lot when you are not in synch with the leadscrew. You may run the risk of cutting a new thread partway into a shoulder of the existing thread. Can't happen, you say? I've seen it, the P.O. of my lathe did that, I had to replace the halfnuts. You need the threading dial to do it right. It shows the exact moment to engage for your thread pitch. Since you don't mention a dial, I will assume you do not have it. In that case, you have to leave the halfnuts engaged and reverse the leadscrew to be sure to stay in synch with the thread you are cutting. Same as with metric using conversion gears. If you DO have the dial, you are always safe to engage on the same dial mark. Depending on the dial marks, the procedure varies. I will assume you have 4 marks, in which case you engage on any mark for even threads, on numbers for odd, on same mark for half threads (like 7 1/2 tpi or whatever). Jerrold -------- Date: Fri, 18 Apr 2003 00:17:59 -0400 From: "Rigrac" Subject: Re: Proper procedure for engaging half-nuts on 6" Jerrold: Strongly disagree. A properly prepared split nut that has a good sized relief at split and has leading thread properly relieved which is to grind away the sharp first thread until thread has a bit of width to it will NOT pick up half way down thread. When engaging split nut you must put gentle pressure down on engaging lever until nut "lines" up with screw and then engagement will be smooth. The only time we leave the split nut engaged and reverse the spindle is when we are either cutting a double start thread or when cutting a metric thread on an imperial machine. Ron ------- Date: Thu, 17 Apr 2003 23:41:25 -0500 From: "jerdal" Subject: Re: Proper procedure for engaging half-nuts on 6" Sorry you don't agree, it is still true. The machines you are used to must be good industrial types, well maintained. These little Atlas etc machines are not made as well, and you absolutely CAN screw them up. As I said, it is no good saying it can't happen as I have seen the results. Note also that I said "if you have no dial", which is true. I don't see how you can easily pick up a finer thread without a dial and without using the equivalent, like chalk marks etc. That I didn't want to go into. The skill required is not shown by the question being asked in the first place by the poster, who is presumably just starting out with his machine. You know that one can't just close the halfnuts anywhere and pick up any old thread of any pitch. And, don't forget a lot of these little machines are bought when already nicely worn by a P.O. who wasn't as skilled as you, So they are already worn, with who knows what pattern of wear, chips, etc on the nuts. When the P.O. got done with it, do you really think the nuts still have the proper form, lead-in etc? Mine did not, it was worn with two threads, one deeper than the other. The dial showed the original one. I don't know what the guy did, but he messed it up. If he could, others can. Asking a new user to figure out all that is silly. Best to just do it by the book and get cute about it later when the skill level is higher. As you are aware, if you have a dial, as you should to do any serious threading with reasonable ease, you need not worry, as the proper moment is always shown by the dial if it is set up right. Jerrold BTW, some nuts engage straight, sliding into mesh, others close on a somewhat circular path around a pivot. The ones which slide closed mesh all at once, and the leading thread has less influence. Ones that pivot closed have more influence of the first thread, as it is the first to engage. Then the leading thread form is more important. Some S-B pivot closed, most or all AA/109 types pivot closed, Logan slides closed. I think most if not all Atlas slide closed in a straight path. The Logan I have will indeed close partway and stop if you miss the proper moment on the dial. That probably depends on the looseness and wear of nuts and screw and nut-cage slideways. Threadform on this set of nuts and the screw is still good, I replaced the bad ones. So it is possible. ------- Date: Fri, 18 Apr 2003 05:24:18 -0000 From: "azbruno" Subject: Re: Proper procedure for engaging half-nuts on 6" Well, it appears the answer was not as simple as I thought when I posed the question. I do have a threading dial, and will figure out how that works. But the question was posed independent of threading; I was thinking about using the leadscrew for simply running the carriage across. My thought was that depending on how hard or quickly the engagement lever is moved and where the half-nut threads align to the leadscrew, there might be potential for stripping the half-nut threads. I'll reread this exchange again in the morning. Bruno ------- Date: Fri, 18 Apr 2003 09:33:09 -0500 From: "jerdal" Subject: Re: Re: Proper procedure for engaging half-nuts on 6" > there might be potential for stripping the half-nut threads. Stripping is unlikely. Wear is certainly possible. Your 6" has a much finer thread on the leadscrew than larger machines, which may have an 8tpi or 6 tpi or even coarser. So there is less material in each thread and wear occurs faster. Obviously there are certain points where the nuts will close, and others where it will not. Attempting to close where it will not only wears the tops of the threads in nuts and screw as the screw turns inside the nut until alignment is reached. The best policy is to watch the thread dial and close when a mark comes past, simply because then there is no wear on the side or top of the threads as you close. But you CAN use the technique Rigrac suggests if you are careful. That is for feeds, not for threading (when you have to be in synch with the partly cut thread). Dial is best for threading, though there are some other approaches to correct synch. I don't use my leadscrew for feeds unless I have to, as it does wear and eventually reduce the accuracy of the screw. I have seen leadscrews worn down to where the threads were rounded and thin, usually right near the headstock. Larger machines have a separate feed rod, or drive the feed from a keyway in the leadscrew. Mine has only crossfeed (facing feed) off the keyway, not turning feed. If you have a handwheel it is good to use that for most movement, using the leadscrew for what it is best at, threading and fine feeds. Jerrold ------- Date: Fri, 18 Apr 2003 16:33:55 -0400 From: "John Glowacki" Subject: Re: Proper procedure for engaging half-nuts on 6" My 12x36 101.07403 was used by my father for thirty some years in his small machine shop. I learned to use this lathe before I was ten. The half nuts on this lathe were very rarely used for thread cutting. They were used all the time to engage the carriage powerfeed when turning or boring. The thread dial was normally in the up position, meaning disengaged and not turning. To my knowledge, the half nuts have never been replaced. There is considerable wear, but they still work and there is no extra set of threads worn into them. The thread dial is only needed to time the engagement of the half nuts to keep a thread cut in sync. Otherwise, drop the half nut lever at any point to start the powerfeed. John Glowacki ------- Date: Fri, 18 Apr 2003 21:50:56 EDT From: catboat15x~xxaol.com Subject: Re: Digest Number 1444 If you don't just mash down on the engagement lever you can feel when the proper point is reached. Put a small amount of pressure on the lever and when the half nuts are in the proper relation to the lead screw the nuts will drop in on the threads. John in the high desert of California ------- Date: Sat, 19 Apr 2003 03:03:34 -0400 From: Stan Stocker Subject: SB clutch VS halfnuts WAS: Re: Re: OBJECT OF A THREAD DAIL You use the clutch for fine feed. There is a reduction ratio built in due to the worm and wheel in the apron. On my SB13, it's 4:1, so if the gearbox is set for 224 TPI, and the clutch is used rather than the halfnuts, the advance is just proud of 1 thou (0.001116 for you sticklers for detail!) per spindle revolution. The threading chart probably specifies either fine feed rate or the ratio to apply to figure the feed rate. To find the feed rate based on ratio, take the inverse of the gearbox or change gear TPI (1/TPI), and divide by the ratio (4 in my case, different on some other models.) In this case, 1/224 = 0.004464. 0.004464/4 = 0.001116 inch of carriage advance per revolution of the spindle. You could also look at this as 896 TPI, so if you prefer, multiply the TPI by the ratio, then take the inverse. 1/(224*4) gives the same result. This also indicates why you need some tip radius on your cutting tool. If you had a knife sharp 60 degree point on the cutter, and the apron and rack were perfect with no lost motion, you could, in theory, cut a 896 TPI thread this way. In reality, you just get a rough surface (a wobbly torn 896 TPI thread) if you don't put a bit of radius on the tip, but it's a fun thing to think about :-) Model C SB lathes don't have a clutch, power feed is via the half nuts just like the Atlas, so you set up the gear train for the feed rate. Cheers, Stan ------- Date: Sat, 19 Apr 2003 17:49:53 EDT From: anthrhodesx~xxaol.com Subject: Power Feed [Was Re: OBJECT OF A THREAD DIAL] In a message dated Sat, 19 Apr 2003 05:33:02 -0000, Ken writes: << Interesting exchange concerning halfnut engagement; one question, sorta off the subject, but sounds like someone here probably would know, should you use the halfnuts on a SB or the clutch if you aren't threading? >> Stan pretty much covered it but, so you'll understand the mechanism: The change gears and or gearbox drive the leadscrew at whatever ratio has been set up. If you engage the half nuts the carriage will be driven at that ratio times the pitch of the leadscrew. So if your gear train/ gearbox are set for a 1:1 ratio and you have a .125" pitch leadscrew (8 TPI) the carriage will traverse at .125" per revolution of the main spindle. If you set up a 1:2 ratio (Spindle turns once, leadscrew turns half revolution), with the same .125" pitch leadscrew the carriage will traverse .0625" per revolution of the main spindle (since the leadscrew has only made a half revolution the carriage will only traverse half the .125" pitch of the leadscrew). Let's leave the half nuts open but engage the 1:1 gearing to the leadscrew. The leadscrew will still turn at the same rate as the spindle but the carriage will not traverse under power as there is no engagement between the spindle and the carriage. However, besides the half nuts, there is a gear of some sort mounted concentric to the leadscrew and with a key that engages the keyway running the entire length of the leadscrew. Whenever the leadscrew is being driven by the change gears/gearbox this concentric gear is being driven through its key, even if the half nuts are disengaged. On an Atlas this concentric gear is a 45 deg. bevel gear driving another 45 deg. bevel gear mounted to the apron; on a South Bend the concentric gear is a worm which drives a worm wheel. But in both cases the result is that when the leadscrew is turning a gear on the back side of the apron from which motion can be taken to drive the cross slide. The Atlas is limited to using the apron gears for cross feed but many lathes, such as the South Bend, can also use the apron gears to drive the carriage along the length of the bed, thus reserving the half nuts for screwcutting where greater precision is required. On the SB, when the half nuts are engaged a pin is shifted laterally in the apron to prevent engagement of the power feed via gears. And vice versa, when the gear feed is engaged the pin is shifted in the other direction to prevent engagement of the half nuts. Leaving the half nuts disengaged, there is a lever on the front of the gearbox with 3 positions: center is neutral (where the half nuts can be engaged), up engages longitudinal feed of the carriage, and down engages cross feed. The drive when using the gear feed is: leadscrew drives worm which drives worm wheel, gear on same shaft as wormwheel (driven through an adjustable clutch) drives selector gear, selector gear is disengaged from all later gears in neutral, is swung into engagement with the carriage wheel gears in the up position, or is swung into engagement with a gear which drives the cross feed screw in the down position. Different rates of longitudinal or cross feed are selected through the change gear/gearbox ratios multiplied by a fixed ratio inside the apron. Stan said the ratio on his SB was a 1:4 reduction but that's relative to the leadscrew pitch. In fact the actual ratio would be 1:32 because it does't involve the leadscrew pitch at all. Still, it's convenient to think of it as 1/4 the screwcutting pitch or 4 times the TPI. Looking at SB's "How to Run a Lathe" it appears that there is another reduction relative to power longitudinal feed of about 3-1/2 to 1 on the power cross feed. Does any of the above help? Anthony Berkeley, Calif. ------- Date: Sat, 19 Apr 2003 06:55:44 -0500 (CDT) From: dswrx~xxwebtv.net Subject: Re: Digest Number 1443 On the subject of half-nuts, threading dials and such, I would like to remind owners of the 6" (don't know if it applies to other size atlases) to check every once in a while the tightness of the screws holding the left hand leadscrew support. This keeps the leadscrew in alignment with the spindle. If it is loose, it can do nasty things to a threading project. 8-) Another thing to check once in a while... the threaded collar that adjusts the end play of the spindle. Leo (pearland, tx) ------- Date: Sat, 19 Apr 2003 19:21:25 -0700 From: "Bob May" Subject: Re: OBJECT OF A THREAD DAIL The thread dial just indicates where the lead screw is in relationship to the half nuts inside. When you are on a mark on the thread dial, the half nuts will engage the lead screw with no problems running down a slop of the thread of the lead screw while the half nut is engaging. The numbers are there as when you are threading finer threads, the lead screw needs to be in a particular alignment with the spindle and thus you will need to wait for that number to come around again. Try it for various threads on a bit of stock to see what happens. Needless to say, as the lead screw turns, the relationship between it and the table that gets driven by it change until the half nut is engaged and this little dial indicates where that contact is best made. The machinist that works the thread dial best will just flick the halfnut lever with a quick touch at exactly the right time and not apply any real force to the halfnut engagement lever to get the tool moving towards/away from the headstock. Bob May http://nav.to/bobmay NEW! http://bobmay.astronomy.net ------- Date: Mon, 26 May 2003 12:44:45 -0400 From: "mertbaker" Subject: Re: 109 half nut [atlas_craftsman] > Has anyone found a way (easy), to repair or replace a 109 half nut??? > Mine is worn on one side, I was thinking of filling it with brass & > trying to re-thread it,, I don't know how to hold it straight to send > a tap through though....... > What is the thread size on the original Half nut?? > Any help would be welcomed, thanks in advance John One, maybe a couple of the epoxy/threadlocking co.s make a thread restoring product. I have used it to restore threads on a very worn cross slide nut on a lathe. The replacement nut was 35 bux, and the epoxy was only 5. I bought the stuff at an auto parts store, and it seems to be a standard item. I think the brand I got was loctite, but I'm not sure. Anyway, you clean the half nuts really well with a degreaser, smear the stuff on the worn threads, coat the leadscrew with release agent, and clamp the halfnuts closed. Wait the required time, (I think it was 5 min.), and open the nuts. Let it cure for the specified time (overnight?) and then trim off any excess. Supposed to equal grade 5 threads. You do have to follow the directions exacly for good results. Do not ask how I happen to know this. Mert ------- Date: Mon, 26 May 2003 16:30:15 -0400 From: "mertbaker" Subject: Re: 109 half nut > I have filled the half nuts with brass and have re-tapped (8tpi acme) to keep the half nuts together I soldered them together with a 1/16" gap this this worked OK I got the tap from "tracy tools" for £22.00 < That would work on most half nuts, but not on the 109, which has the two halves cast into the halfnut lever, about an inch apart along the leadscrew. Mert ------- Date: Sat, 21 Jun 2003 23:33:52 -0000 From: "jimmac70817" Subject: Re: thread dial indicator for craftsman 109 [atlas_craftsman] > Are there any thread dial indicators available that > will work on a Craftsman 109? Chris Hamel You can adapt the thread dial that comes on the hf 7x10. Buy it at Littlemachineshop.com Jim ------- Date: Sun, 22 Jun 2003 18:39:40 -0000 From: "jimmac70817" Subject: Re: thread dial indicator for craftsman 109 Chris Hamel wrote: > Jim, Thanks for the info. I checked out the web site and > found that it appeared I would have to order three > separate parts. Dial, shaft and housing. Is this > correct. Also, how much is involved in adapting this unit? Looks like you are correct on the parts, they used to sell it as a unit I think for 19.95. To install it you have to make a small bracket to set the vertical height. If you can get an original that's how I would go. If I had seen them at Bill's site I would have referred you there. Good luck Jim ------- Date: Sat, 15 May 2004 01:27:42 -0000 From: "jjjorg1" Subject: Re: Half nuts help [atlas_craftsman] Hi Jon. I replaced the half nuts on my 10f Atlas several years ago. I ordered a new set from Clausing Service Center in Goshen Indiana. The package did come with instructions. Basically, for my lathe, I removed the tailstock and lead screw bearing, opened the half nuts and slid out the lead screw (be careful not to let the feedgears and shift collar drop out from underneath the feedgear assembly when you remove the lead screw). I then removed the carriage and unscrewed the halfnut housing and removed it from the apron. Be careful not to lose the steel ball and spring. Then you remove the setscrews on the half nuts, slide the half nuts out, lubricate and slide the new ones in (after removing any flash), screw in the half nut setscrews, align the nut screws with the guide, place and grease the spring and steel ball, align and tighten the housing screws and check alignment and operation, place the carriage, leadscrew and gears and shift collar, lead screw bearing and tailstock, lubricate the lead screw and bearings, and test operation of the half nuts and make adjustments. There may be some variation with different designs and you'll be able to get more information from Clausing and the Atlas_Craftsman group here on Yahoo. Good Luck! Joel ------- [atlas_craftsman] Re: "File a taper on the replacement half nuts as pre the book" Posted by: "Rexarino" rexarinox~xxgmail.com Date: Fri Oct 17, 2008 9:59 pm ((PDT)) On Fri, Oct 17, Thomas wrote: > Hi Group. I really appreciate the fast responses to my post. I have > reposted trying to get more information on this taper thing. I have > three sets of half nuts and none has a taper. The more worn the 1/2 > nuts are the easier they are to engage. The wear on my lead screw is > normal; ie. more wear closer to the spindle and the 1/2 nuts close > easier near the spindle. So this taper instruction makes sense; at > least IMHO. Thomas Thomas, on my 12" lathe, with new half nuts or with the old ones, it is possible to partially engage the half nuts by jamming them down on the lead screw at the wrong place - somewhere between the correct engagement points. This moves the carriage, but the half nut lever isn't fully engaged. Is that what you are doing?. Try this: with the lathe turned off, rock the carriage longitudinally back and forth about 1/4 to 1/2 inch while applying light pressure to the half nut engagement lever. When you find where the half nut falls into place and the lever easily moves between engaged and disengaged, then look at your threading dial. If the index line on your threading dial corresponds with one of the 4 major lines on the dial, then you can use the threading dial to show you when to engage the half nuts. To use with the lathe running, you start applying pressure on the engagement lever just before the thread dial index line aligns with a quadrant line on the thread dial and follow through as the lines "line up". If there isn't any place that it easily engages with the lathe stopped, then loosen the tiny screw directly above the boss in the apron where the lever pivots, and try again. That screw pushes a ball against a dimple on the engagement lever to provide a detent - to hold the lever disengaged when you want it disengaged. It can be tight enough that engagement isn't smooth. If it engages easily while the lathe isn't running, but the thread dial doesn't line up, leave the half nuts engaged, then loosen the thread dial mounting screw, swing it out from the leadscrew, turn it one tooth, and reengage it. Look to see if it is aligned. Mine would not align at any tooth position, so I used shim washers under the thread dial mount to move it away from the carriage a small amount. This allowed me to align the quadrant marks with the index line. When I use the thread dial, my half nut engagement is usually smooth. My new half nuts only got a spit shine where the threading die had left a rough edge, and they work very well without a taper. Rex ------- Re: "File a taper on the replacement half nuts as pre the book" Posted by: "pflatlyne" pflatlynex~xxyahoo.com Date: Fri Oct 17, 2008 10:47 pm ((PDT)) > Thomas, on my 12" lathe, with new half nuts or with the old ones, it is > possible to partially engage the half nuts by jamming them down on > the lead screw at the wrong place - somewhere between the correct > engagement points. I kinda assumed that just jamming them down like that was a bad idea and stressed the half nuts unnecessarily. (It so tempting to make some off color and painful sounding pun at this point.) It seems it goes in easy if the screw is moving. When I was playing around with it with the mill off and seeing how everything fit together, I moved the longitudinal feed handle a little so it slipped easily in. ------- Re: "File a taper on the replacement half nuts as pre the book" Posted by: "Rexarino" rexarinox~xxgmail.com Date: Fri Oct 17, 2008 11:36 pm ((PDT)) You know, I probably should have suggested that the reason I have new half nuts was because they appear to have been jammed, therefore it might not be a good idea to repeat that experiment... Off color painful pun noted and giggled at, no need to elaborate. My point, more simply stated, was: see if the new half nuts are easy to engage anywhere; if not, check the detent to see if it's too tight. If they are easy to engage at rest, set up and use the thread dial while in motion. Add, "don't jam them" Regards, Rex ------- Re: "File a taper on the replacement half nuts as pre the book" Posted by: "jerdalx~xxsbcglobal.net" Date: Sat Oct 18, 2008 6:54 am ((PDT)) I am not at all clearly understanding the "taper" to be filed in/on/ whatever the new halfnuts. Sounds like creating some sort of "pre-worn" condition on the thread tips... trying to allow them to engage even if "offset" somewhat at the time of engagement. BUT...... For best results, they should be as close as possible to fitting in exactly one position. If you ever try to cut a 48tpi or finer thread, this will become abundantly clear... very quickly. The error in some halfnuts due to slop can wipe the threads right off the part if not always taken up before the cut starts. If you DO let the halfnuts partly engage, you will probably eventually wear a groove, or "step" in them. Now there will be two possible engagement positions, and not just one. The difference between them will only be a slight movement of the engagement lever. This is more likely since the sort of person who is that careless on a regular basis is also the type who oils the leadscrew once every decade or so whether it needs it or not. I suspect I can guarantee that such a "step" will oneday make you very angry... as the threading tool tracks accurately down the crest of the almost completed thread, or worse yet, snaps off due to suddenly taking an 0.125 depth of cut in 4140... as well as ruining the workpiece. If you want to be sure there is no "fin" or burr on top of the threads of the new nut, fine. That is a good plan, as such a burr will break off and shift the carriage position at some bad time. But modifying the shape to fit easier sounds like a particularly poor idea, unless I am completely misunderstanding. JT ------- Re: Threading dial on Atlas 618 [atlas618lathe] [or possibly other lathes] Posted by: "azbruno" azbrunox~xxyahoo.com Date: Sat Oct 25, 2008 11:32 am ((PDT)) Gene King wrote: > I am rebuilding a Sears/Atlas 07301 and the threading dial is very > tight and doesn't turn easily. I haven't figured out how to > dis-assemble it. Does the gear or dial screw on or is the assembly > pressed together? I have soaked it with penetrating oil and it still > is very hard to turn. GeneK I've had the same thing happen. Taking it apart is not a good approach. Try a hair dryer to heat up and loosen any residue. Also keep soaking, maybe kerosene will do it. Eventually you'll get it going. I have also found that the metal on the top of the dial is soft, so if you tighten it hard onto the carriage, it can deform the left edge of the metal into the top of the dial to interfere with movement. Bruno ------- Re: Threading dial on Atlas 618 Posted by: "ajxnagy" ajxnagyx~xxsbcglobal.net Date: Sun Oct 26, 2008 10:19 am ((PDT)) In cases where there is gunk from oxidized oil it is best to use something like automobile carburetor or choke cleaner if you can still find it and if you are not worried about dissolving paint. Acetone or Methyl Ethyl Ketone or laquer thinner are also excellent for dissolving oxidized oil or varnish. Kerosene may eventually work but my experience is that it won't. Sometimes the wife's fingernail polish remover is worth a try if she will tell you where she keeps it! Treat all of these solvents with respect using good ventilation and keeping away from ignition sources. ------- Re: Threading dial on Atlas 618 Posted by: "Robert Rochelle" irene4popsx~xxyahoo.com Date: Mon Oct 27, 2008 7:16 am ((PDT)) The wife's fingernail polish remover is primarily acetone. Buy a quart at the hardware store & you won't have to ask. Robert Rochelle ------- Re: Threading dial on Atlas 618 Posted by: "Uldis Stulpins" u_stulpinsx~xxyahoo.com Date: Sun Oct 26, 2008 5:19 pm ((PDT)) I disassembled and painted the threading dial on my Craftsman 109.20630 lathe earlier this week. It is a press fit, as I assume are most others of this style lathe. I used a block of material with a hole slightly larger than the dial face, along with a 1/8" gauge pin in a small arbor press to effect the removal. A screw-on-type assembly would have required an awkward fixturing set-up during production, plus it doesn't lend itself well to an application which typically is used to cut both right and left-hand threads, so the odds would favor a press-fit for your model also. The recess in the body of the dial proper for my dial face is a little deeper than the thickness of the dial face itself, so re-assembly was a snap. Pressing the parts together after the re-paint/re-lube took advantage of this built-in axial clearance-producing feature. Uldis ------- Re: Threading dial on Atlas 618 Posted by: "Uldis Stulpins" u_stulpinsx~xxyahoo.com Date: Mon Oct 27, 2008 7:18 am ((PDT)) I'm not sure why using an arbor press or vice to just disassemble the thing is not a good idea, as was cautioned earlier. Then you can SEE what the commotion is all about. Then use the lacquer thinner, acetone, steel wool, wire brush, etc. to clean it up. Coat the shaft with some lithium grease, re-assemble and be done with it. (I repainted the body of mine in the mean time, and did the plated dial face in flat black, removing the paint from the numbers and quadrant lines after it dried with a flat tongue depressor soaked with lacquer thinner to make it more readable.) Really, taking it apart and reassembling it is not a strain at all. It was made by human beings and it can be refurbished just the same. If the body has gotten bent enough to impinge on the dial face itself, it was probably because the thing was not oriented into the correct, clearancing position when "off" to avoid getting slammed into the head stock during exuberant saddle movement and got bent that way, not because the 1/4-20 screw was tightened too much. My recently eBay purchased, replacement unit does show evidence of being previously slammed into a head stock, but at the screw boss, not the dial face surround. (Interference at this point very likely being a result of variations in production tolerances. I have 2 - 109 head stocks which visually vary as to metal thickness, and potential to interfere with the threading dial body, in this area, right next to the lead screw where the threading dial may, or may not, strike the head stock.) Uldis ------- Re: Threading dial on Atlas 618 Posted by: "Gene King" geneking2001x~xxyahoo.com Date: Sat Nov 8, 2008 6:00 pm ((PST)) > Don't know how far you've progressed with loosening up the threading > dial - I would suggest you try to find some heptane as it is one of > the better solvents for hydrocarbons. Soak it in the heptane for a day > or two, then add some oil (almost anything will work) and work it in. Mike, I have gotten the dial apart and found that it had been mis- assembled previously. They had raised a burr on the shaft that bulged down into the hole and was binding the shaft from turning. I'm seriously thinking of making a new housing from 6061 aluminum. GeneK ------- restored half nuts, great success [atlas_craftsman] Posted by: "Pip" pipster1979x~xxyahoo.com Date: Wed Feb 17, 2010 10:31 am ((PST)) Hi all. The other night I was doing some boring in some aluminum, and it started turning out like crap, soon I realized what was going on. My half nuts were slipping and the carriage would stop here and there. I proceeded to take the half nuts off and clean them out. At the left and right of the lead screw it seemed to work ok, but in the center it would stop completely. I remembered seeing a post in the file section on restoring half nuts, read thru it and looked at the pictures. So I thought well what have i got to lose. So first I had to find a piece of brass that would do, then I turned the outside down to .568. Then I drilled out the center to around 0.450. Then I had to grind a custom boring bar to match the threads on the leadscrew (I used a 5/16 allen key grinded down) -- fit the boring bar to the leadscrew really nicely. Then set up the gears for 16tpi. Did a few passes and test fit on the lead screw. Kept doing a few passes and trying till it fit on just nicely without play. Then I took the carriage off and got my Dremel out. Thinking to myself, after this there's no turning back lol. Put the largest drum sander I had in the Dremel which measured about .589 and put it in between the half nuts, turned it on, and eased the half nuts to it and started working it in and out of the half nuts -- every so often adding more pressure with the half nut lever. Kept doing this until my brass threaded sleeve would fit in the half nuts clamped down. Then I drilled a 1/8 hole thru both half nuts, plastered them both with JB Weld, started the sleeve on the leadscrew a few turns by hand. Placed the carriage back on the lathe, lined it up with the sleeve and clamped down the half nuts with the lever and reinstalled the leadscrew end bearing. I used a lot of JB Weld and was worried that it may have gooped over and stuck to the lead scew. Luckily I went back to it the next night (24 hours later) and turned out by hand. So I removed the carriage, took my largest cutting disk in my Dremel and cut the sleeve in between the half nuts. Then all I had to do was shave the brass a tiny touch to bring it flush with the rest of the half nuts. Installed everything back on the lathe and prayed to God that it would work. To my surprise, great success -- worked perfectly. I strongly suggest anyone with worn out half nuts to do this. It works great and isn't hard to do. And the brass will outlast that soft aluminum. I find it feels a lot better now as well. ------- NOTE TO FILE: There is some good information about Atlas half nuts in the three files: "Atlas Repair or Fitting" and "Atlas Parts General" and "Atlas 618 Gems" some of which could be applied to other lathe brands. ------- Threading dial [atlas618lathe] Posted by: "dwoodcutter" dougdomerx~xxyahoo.com Date: Wed Jun 30, 2010 9:53 am ((PDT)) Hi Guys- I have a question regarding the threading dial. On my lathe the dial is rather hard turning as the race/holder?, that it sits in appears to be bent so it is not concentric with the dial and binds. My question is how much play should be in this unit? Thanks Doug ------- Re: Threading dial Posted by: "David Beierl" dbeierlx~xxattglobal.net Date: Wed Jun 30, 2010 1:35 pm ((PDT)) Mine (a sixteen-tooth one) has barely discernable side play at top and bottom. End play is taken up by the oiling pad beneath the dial. It takes maybe an ounce-inch to turn the gear -- I attribute this to the oiling pad. Over seventy years the zinc housing has gotten squeezed a little so that the rim with the two index marks on it has pressed close to the dial at the sides and bowed away a little at the middle. Occasionally a little chip gets in there and makes it scratchy. But the only problem I've ever had with difficult as distinct from scratchy turning was when I started using the lathe a decade ago and it had been unused for probably at least five years. The dial was very stiff and it took many treatments with lube oil and MMO to get it working smoothly. Today I might be tempted to press the gear off the end and pull the shaft to get it cleaned up. Yours, David ------- Re: Threading dial Posted by: "Dean" deanwx~xxbmi.net Date: Wed Jun 30, 2010 2:09 pm ((PDT)) Mine was kind of stiff turning too. I pushed off the gear, removed the shaft, and ran a reamer through the body. That pretty much took care of it. It will turn easily. ------- Re: Threading dial Posted by: "dwoodcutter" dougdomerx~xxyahoo.com Date: Thu Jul 1, 2010 12:28 pm ((PDT)) > Over seventy years the zinc housing has gotten squeezed a little so that the rim with the two index marks on it has pressed close to the dial at the sides and bowed away a little at the middle. < David -- This is exactly what is happening with mine. Guess I'll just keep lubing and working it. Thanks. Cheers Doug ------- Re: Threading dial Posted by: "Rob Chapman" chapman49682x~xxyahoo.com Date: Thu Jul 1, 2010 12:43 pm ((PDT)) Doug: My thread indicator behaved exactly that way when I got my 618. I surmised that at one time, the shaft got sticky, causing the gear to slip on the feed screw. This made the operator think that the bolt holding the indicator to the carriage was not tight enough -- so he tightened it too tight and made the housing oblong. Having learned too many times that white metal can only take one "bending event" at most, I knew that trying to make it round again would only result in another eBay purchase. I got lucky and was ably to fix mine by taking it apart and running a drill through the housing. If memory serves, I held the thread indicator unit loosely in a vise, resting on the shoulder near the top. I gently tapped the shaft and gear down and out with a punch. This allowed me to ream the hole lightly with a drill, getting rid of the decades of accumulated dry oil and crud and to make the hole round again. You might have to grind a bit on the circumference of the dial if the housing was made too oblong (I didn't have to). I oiled the shaft liberally, put it back together (being careful to not tap the dial on too far), and it now works like a champ. ------- Re: 618 Thread Dial Disengaging [atlas618lathe] Posted by: "David Beierl" dbeierlx~xxattglobal.net Date: Thu Jul 7, 2011 9:55 am ((PDT)) At 02:04 PM 7/6/2011, Ed Marsalis wrote: >Am I reading the process correctly to understand the tread dial is >NOT supposed to rotate while the half nuts are engaged. If that is >the case, I am confused as to its value in returning the carriage to >the starting point... Ah so. The dial indicates phase between the spindle and the carriage. When the tumble reverse and half nuts are engaged the carriage assumes a fixed relationship to the rotation of the spindle; for a given position of the carriage there is only one (with backlash taken up) possible angle of the spindle. For a given spindle angle there are a number of possible carriage positions corresponding to successive threads at the selected pitch. Since the phase relationship is fixed, the dial is also. When you disengage the nuts at the end of a cut you destroy that fixed relationship, but the dial begins to rotate as it continues to indicate phase which is now changing. Depending on the thread you're cutting, you may be able to re-engage at any of the marked points or only at two opposite ones, or only at the same one you started with. If you choose the wrong one, you'll find that the tool is in the right place at the wrong time (or spindle angle, actually) and you'll wreck the thread or tool or both. You can't choose wrong for the first cut as it's that cut that defines the phase relationship. Hope that helps. Yours, David ------- Re: 618 Thread Dial Disengaging Posted by: "Leo Reed" lpreedzonex~xxearthlink.net Date: Thu Jul 7, 2011 10:45 pm ((PDT)) Best advice... if you are not in a hurry, always engage on the same mark! Leo (pearland, tx) ------- Re: 618 Thread Dial Disengaging Posted by: "David Beierl" dbeierlx~xxattglobal.net Date: Thu Jul 7, 2011 11:42 pm ((PDT)) At 06:16 PM 7/7/2011, Ed Marsalis wrote: >Would this process then ?require? the thread >dial gear to ?appear? to be disengaged and not >rotating as the carriage traverses? When the half nuts are engaged, the carriage and the leadscrew are locked together and the threading dial *cannot* turn because the half nuts are pulling the carriage along the screw as it turns. There is no relative motion between the lead screw threads and the carriage, and this relative motion is what the dial indicates. > When the thread dial is then reengaged at the > end of the cut and the carriage returned to a > ?0? position, it will then be in ?phase with > the desired starting spot (regardless of its > physical location along the lead screw?so to speak? I'm not completely clear what you're saying. The *thread dial* must stay engaged on the lead screw at all times during thread cutting, or its purpose is lost. It exists only to allow you to conveniently disengage and re-engage the half nuts without losing the phase relationship between the spindle rotation and the carriage travel. Again, the tumble reverse must also stay engaged for this to succeed. >Wow this is complex? Once you've had your hands on it a time or two it gets simpler. And as Leo said, easiest to begin with is to always engage on one particular mark. Once you're comfortable with that you can branch out and save time by using additional marks when appropriate. But my suggestion for playing around would be to start by setting up for an 8 tpi thread. That's a 64-tooth idler from the 32-tooth tumble reverse gear, followed by a 32/64 compound gear and a 32 on the lead screw. The spindle will rotate twice for each lead screw rotation. Engage at the 0 mark on the dial and take a cut a few thou deep to mark out the thread, then set the tool so it almost touches the work and experiment with engaging the nuts at different marks on the dial, watching to see where the tool ends up as it traverses the work. If you have a sixteen-tooth gear on the threading dial you'll be able to engage the nuts at sixteen positions around the dial. Then set up for 10 tpi - change the lead screw gear to 40 -- and do the same. Finally change the screw gear to 36 to get 9 tpi and try that. If you're feeling adventurous you could set up for 11.5 tpi and (I think) find that you are limited to a single mark. But the first three you can get by changing only the screw gear, once you've set up for any one of them. Yours, David Beierl -- Providence RI USA Atlas 618 6"/3/index.html" lathe ca. 1941, shiny-new Taig mill. ------- Re: Carriage Half Nut Resto... [atlas618lathe] Posted by: "calvin" moosebakerx~xxbellsouth.net Date: Mon Sep 19, 2011 10:34 am ((PDT)) "none" wrote: > Has anyone here had luck restoring the 618 carriage half nut threads with some sort of epoxy, filler, etc ??? The ones on my lathe, part#: M6-12A are about toast. These small parts are used for both threading and power feeding on the 618 Atlas so they see a lot of use. Thanks, Gary in AZ < Gary, I have done it useing JB Weld. Threads were still there but badly worn. Clean part with Acetone or something to remove oil. Clean a less worn area of screw, spray screw with release agent, I used pan spray. Put JB On part, don't need much, let it begin to set. Press onto screw, opposite the slot. Be sure it seats into the threads, clamp lightly. It has held up for several years light use. chiphead42 ------- [Article about alternative metal lathe half nuts. Conversation title was misspelled but has been corrected here after the first message.] haft nuts [atlas_craftsman] Posted by: "nonparadigm" nonparadigmx~xxyahoo.com Date: Mon Jan 9, 2012 9:01 am ((PST)) Told my wife I needed to buy another half nut and she replied, with the half nut you bought last year, this will make you a total nut!!! On a more serious note: Looking for some information on half nuts. Has anyone in group mastered making these nuts from a different material or a redesign? I go through at least one per year and now need another. Buying these off the internet is getting expenses at about $60.00 a pop, I was thinking about making one out brass or bronze but not sure if possible. The (three quarter inch) lead screw seems to be OK, and I do run some projects at a high speed and this may be a factor in faster wear out. Just thinking outside of the box. Thanks Dennis ------- Re: half nuts Posted by: "Guenther Paul" paulguenterx~xxatt.net Date: Mon Jan 9, 2012 9:07 am ((PST)) I have seriously been thinking of making some 1/2 nuts. I am undecided on the material to use. Some years ago we made brass parts for a foundry and used fermex. It does not wear in normal conditions. It was use because the brass parts came in contact with foundry sand and out lasted bronze 10-1. GP ------- Re: half nuts Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Mon Jan 9, 2012 10:01 am ((PST)) Wow! How much turning do you do? I have never worn out a set of half nuts, and used the Atlas/Craftsman lathes for several decades. I've never even seen any sign of wear over the time I had them. Maybe your leadscrew is bad, a worn area will have threads that get narrower along the axis, then get wider again. This loads only one thread of the nut against the screw, and could make it wear faster. Keeping the screw clean is a problem due to the placement of the screw, a lot of swarf falls on it. Make sure you lube the screw liberally with a clinging oil like way oil every time you use it. I'd always replace the nuts as a pair. But, if you want to make them, what I'd do is make a bronze insert with the thread cut in it, then slice it apart on a bandsaw, axially. Then, you could probably bore out the old pair of nuts, degrease thoroughly and epoxy the bronze threads into the old castings. You'd need to pull the leadscrew and clamp the nuts onto it to align the threads on the two halves. On some larger machines, they have even cast leadscrew nuts out of Moglice, a castable low-friction epoxy made for castable way liners. After regrinding a lathe bed, you machine away a little of the underside of the carriage and cast this stuff to the lathe bed. (You put a mold release agent on the bed first so you can pop it free after curing.) I did this on my 15" Sheldon lathe, and it works great. So, some people have found amazing other uses for this material. I'm not sure how well Moglice would work on the small half-nuts in an Atlas, though, the stress there might be too much. Devitt Machinery is the US rep for Moglice, and they have some photos and info on their web site. Jon ------- Re: half nuts Posted by: "Guenther Paul" paulguenterx~xxatt.net Date: Mon Jan 9, 2012 10:44 am ((PST)) Well here i go again with my question. How much would you all pay for brass 1/2 nuts? The tooling will cost me a few $$$$$$$$ if i make them there will be no inserts they will be all bronze. I don't understand why aluminum, but i guess back when aluminum was started being used they really did not know how long it would last and castings were a lot lot cheaper. I usually i guess over a years time i use my lathe 1 day per week. My lead screw is fine no problem there. GP ------- Re: half nuts Posted by: "James Irwin" jirwin1x~xxaustin.rr.com Date: Mon Jan 9, 2012 11:00 am ((PST)) Aluminum? Half nuts I¹ve seen are die-cast of Zamak. Quite a bit more durable than aluminum. Are you going to make brass or bronze half-nuts? If bronze, do you mean solid bronze (stronger) or Oilite bronze (less strong)? Jim I ------- Re: half nuts Posted by: "Guenther Paul" paulguenterx~xxatt.net Date: Mon Jan 9, 2012 11:09 am ((PST)) Yes i know die-cast is still junk. I will make them solid bronze. GP ------- Re: half nuts Posted by: "James Irwin" jirwin1x~xxaustin.rr.com Date: Mon Jan 9, 2012 2:41 pm ((PST)) On 1/9/12, "Guenther Paul" wrote: > James. Please tell me honestly. Would you pay 3-times the cost of > die-cast for bronze 1/2 nuts nope ------- Re: half nuts Posted by: "Ahz" ahzx~xxinsightbb.com Date: Mon Jan 9, 2012 2:54 pm ((PST)) An easy and affordable way is to make them of Acetal. It requires only a chunk of Acetal (cheap!) and a heat gun. Get thee to the HSM (you ARE a member of the HSM, yes?) and read this thread: http://bbs.homeshopmachinist.net/showthread.php?t=43645 ------- Re: half nuts Posted by: "Doc" n8as1x~xxaol.com docn8as Date: Mon Jan 9, 2012 4:19 pm ((PST)) FWIW i wud give some thot as to WHY the 1/2 nuts were made of zamak to begin with ...MAYBE cost & JUST MAYBE since the lead screw is used as a feed screw, instead of a separate feed rod, they wanted to make sure the 1/2 nuts wore out principally & not have equal wear of 1/2 nuts & LEAD SCREW ...??? ------- Re: half nuts Posted by: "Ahz" ahzx~xxinsightbb.com Date: Mon Jan 9, 2012 4:25 pm ((PST)) Good point. And it's a smart move. Remember, back in the day, the replacement parts were very affordable. And I'm sure it was more cost-effective to cast the halfnuts instead of machining them. ------- Re: half nuts Posted by: "wa5cabx~xxcs.com" Date: Mon Jan 9, 2012 4:40 pm ((PST)) The original die-cast junk in my 3996 have lasted 33 years next week and still work fine. The only reason that I would reluctantly replace them with brass or bronze ones would be if for some reason I had to replace them and couldn't find new originals. Robert ------- Re: half nuts Posted by: "Unchained malady" philip.a.sutcliffex~xxntlworld.com Date: Mon Jan 9, 2012 5:34 pm ((PST)) Why Zamak? The answer lies in the name of the company 'Atlas press Tool Co.' They were not in the business of making lathes originally, they were trying to maximise use of their press production facilities, machine tools were a very suitable candidate, allowing them to cut costs and sell a very affordable machine to a mass market using lots of Zamak pressed components (count them all). The Atlas lathe was an ideal testbed for Zamak metal pressings, the lathes were used under a great variety of conditions and workloads, and proved successful albeit with some problems. The success of the Atlas lathes allowed the company to promote the durability of mass produced pressed components, particularly gears, with accuracy and interchangeability and when WW2 came along it was just what was needed, both in the US and GB. Without Zamak it is unlikely the Atlas lathe would have had the market penetration it did. My Acorn clone of the Atlas has a mixture of Zamak and bronze parts, my UK made bronze half nuts (maybe the ship carrying Zamak nuts got torpedoed) are just as susceptible to wear as the Zamak ones, but they are much tougher, Some Acorn lathes have a bronze feed gearbox, crosslide & compound feed handles and I've never seen broken ones, unlike the Zamak that often gets broken. I just wish my mitre gears were bronze! It was without doubt a cost based decision, and a fortunate one for us revivalists as there are so many around to keep us going. ------- Re: half nuts Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Mon Jan 9, 2012 8:21 pm ((PST)) The Atlas/Craftsman half-nuts are Zamak, which contains aluminum, but also had Zinc and Copper, and is a much better wearing material than aluminum, which makes a horrible nut or bearing. Brass is somewhat better, Bronze is hard as hell and quite long-lasting, but tough to machine. Of course, if your nuts really ARE aluminum, then it is obvious why they are wearing out. Jon ------- Re: half nuts Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Thu Jan 12, 2012 5:22 pm ((PST)) Guenther Paul wrote: > Jon I turned and made several parts from gray iron and as you know that stuff sticks to oil like crazy. I tried and did keep my lead screw clean but i firmly believe the gray iron did it [wore the nuts]. < Well, I was wondering. I think constant machining of gray iron could cause this sort of damage over time. I really have doubts that just SEVERAL parts would do that much damage. You can clean the leadscrew by oiling liberally and then holding a paper towel in the thread while running the leadscrew under power and allowing the thread to pull it down the length of the screw. The keyway does tear up the towel, but it does clean the threads out. I did this after any time I did wood or abrasive stuff on the lathe. It only takes a couple minutes to clean the screw out. Jon ------- Re: half nuts Posted by: "Rexarino" rexarinox~xxgmail.com Date: Thu Jan 12, 2012 9:05 pm ((PST)) Jon Elson wrote: > > Anyone ELSE out there troubled by rapid half nut wear? My experience > > moderating this list for more than a decade is that badly worn nuts > > show up on old lathes from time to time, but I've never heard of > > anyone wearing out more than one set. Jon On Jan 12, 2012, jworman wrote: > That's my experience as well. I bought two sets of half nuts just > after I bought my QC-54 Lathe. That was 40 years ago. > I sold the lathe in September, and I included the 2nd set with the > machine. The first set that I installed were doing just fine When I bought my unused 12" well traveled Craftsman, I was inexperienced with light lathes. During my experimentation with it, I was often able to sort-of engage the half nuts at odd places between the marks on the threading dial. Since the marks on the threading dial never lined up with proper engagement points, I mis-engaged the carriage feed rather more often than was prudent. After 20 years or so, I found that the half nuts weren't in good shape, so I got a new set from Clausing. Last year, after 7-10 years of use, I inspected the new set and they show little wear - but then I had also spaced the thread dial away from the carriage with a washer so it would indicate engagement more accurately. In any case, rapid wear might be caused by mis-engagement (the carriage will move even when improperly engaged) or by slop in the guides, or other reasons, such as a weak or faulty spring and ball in the engagement lever detent, which sometimes lets my lever creep down and partially engage. For what it's worth, the old half nuts have thread crests thinner than the new ones. The remaining crests are full height, and pristine on the side that never sees wear, but deformed and worn on the pressure side. Rex ------- Re: half nuts Posted by: "wa5cabx~xxcs.com" Date: Fri Jan 13, 2012 5:03 pm ((PST)) FWIW, Clausing still has original half-nuts in stock. I bought a pair today. Along with a lower countershaft and bushings. I didn't write the prices down, just the total, but I think the pair of half nuts were $31 and change. The two studs don't come with them and are $1 each. Robert Downs - Houston wa5cab dot com (Web Store) ------- Re: half nuts Posted by: "wa5cabx~xxcs.com" Date: Fri Jan 13, 2012 8:07 pm ((PST)) 01/13/2012 sleykinx~xxcharter.net writes: > That's worth the whole show !! The day will come when they won't have anything left. Or will have gone out of business or been bought by someone who made them scrap all of their old inventory. I think most old lathe owners tend to assume the same thing that I did. The lathe was made in 19xx. The company that made it isn't even doing business under the same name. Just about everything else any of us own, after from 1 to 10 years the company that made it won't even know what we're talking about if we call them for parts. Or are long out of business. Had it not been for another list member, I never would have bothered to try to call Clausing. And as someone else since has reported, they didn't hang up on me when I told them what ancient piece of equipment I was calling about. They didn't still have everything I called about that first time. But they did have about 75% of it, and had 100% of the actual repair parts. What they didn't have were two accessory sets. One item that they did have, the milling cutter holder and drawbar set, was cheaper than what I paid for an aftermarket one on eBay (that I don't like). Same thing today. Two parts I wanted (they weren't for the lathe but for an accessory) they no longer had. The rest they did. Anyway, for the time being at least, if you need a part, call them. If they don't have it, then start looking or making. Two other thoughts WRT Clausing. I got the impression that they may still have some parts made if they sell out. So buying from them might ensure a continuing supply. And they seem to have ready access to at least some drawings of parts they no longer carry. My example is a gear. The 900B, 6630 and maybe 6692 collet closers require installing a modified spindle gear. They no longer have parts for the closers, but in less than a minute this afternoon, Ms Olds looked up and gave me the modification information (dimensions). I'm sure it didn't hurt that I had just bought some parts, was already in their customer database from having previously bought parts, and first asked whether they had the gear in stock. :-) Robert Downs - Houston wa5cab dot com (Web Store) ------- Half nuts not catching [atlas_craftsman] Posted by: "Deloid" deloidx~xxcableone.net Date: Sat Feb 4, 2012 2:53 pm ((PST)) With the lever flipped to engage the threading half nuts (M6-12A) it only engages if I put firm downward pressure on the lever. Are there adjustments for this or are my half nuts just worn out? Thanks ------- Re: Half nuts not catching Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Sat Feb 4, 2012 3:34 pm ((PST)) First, look up there with a light and mirror, or just take the apron off. If this happened suddenly, it is most likely a big chip mashed into the nut threads, preventing them from closing onto the screw. It is good practice to clean out the nut threads every once in a while. It is also possible there is a problem with the scroll or pins that engage the nuts. Jon ------- Re: Half nuts not catching Posted by: "Bruce Freeman" freemab222x~xxgmail.com Date: Sat Feb 4, 2012 3:44 pm ((PST)) Just in case someone didn't know: The half nuts will only engage when their threads are aligned with those of the lead screw. If the lead screw is rotating fairly rapidly when you lower the lever, it will usually engage fairly quickly. However, when the lead screw is rotating slowly, engagement may be slow. If the half nuts don't engage within one revolution of the lead screw, something is wrong. ------- Re: Half nuts not catching Posted by: "Deloid" deloidx~xxcableone.net Date: Sat Feb 4, 2012 5:31 pm ((PST)) Something is wrong Bruce. While not a safe thing to do, I squeezed the half nuts together with my fingers while the lathe was running and they engage properly and work well. The general appearance of the threads in the half nuts is good and there is no debris. I don't know the proper depth of the thread of the half nuts or the screw feed. Jon, can a problem with the scroll or pins alter the tension on these nuts so they don't wrap tightly enough on the screw feed? Dean ------- Re: Half nuts not catching Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Sat Feb 4, 2012 7:53 pm ((PST)) Yes. If the scroll or the pins on the nuts are worn, it will not pull the nuts together enough to engage. I think you will have to take the apron off to find out what is wrong. Pull the leadscrew out from the right end by removing the bracket there. Remove two screws on top of the carriage and the apron should come down. Once you have it off, it will be easy to see what the problem is. Jon ------- Half nut chaos [atlas_ craftsman] Posted by: "crackinbracken" crackinbrackenx~xxjuno.com Date: Fri Feb 17, 2012 8:23 pm ((PST)) I wanted to post the plans for an adjustable half nut replacement for the original Atlas design. Here is the link to the photo, Ya gotta view it in "Original" size to see the detail. (forgive the spelling errors!) I built this and it works so nice, I wanted to share it. Mark o ya, the link to the photo/plans... http://groups.yahoo.com/group/atlas_craftsman/photos/album/137719246/pic /1854878273/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc ------- Re: Half nut chaos Posted by: "inspiro_creo" david.deboizex~xxverizon.net Date: Sat Feb 18, 2012 11:00 am ((PST)) Mark: Even though I don't need a set of half nuts, I applaud your execution. With this setup one can make several sets at a time of brass and have them ready for when one set wears down. Basically attaching the new set to the brackets (slides). Very nice, definitely a keeper. Thank you David ------- Re: Half nut chaos Posted by: "crackinbracken" crackinbrackenx~xxjuno.com Date: Sat Feb 18, 2012 5:49 pm ((PST)) The joy is that the half nuts I made are so thick, you would have a real hard time wearing them out. You just keep shimming them as needed. Takes about 4 min to do. I hate being a slave to the "parts house". Mark ------- Re: Half nut chaos Posted by: "crackinbracken" crackinbrackenx~xxjuno.com Date: Sat Feb 18, 2012 9:21 pm ((PST)) "miner49r" wrote: > Once again, Nice Job. > I have a hard time picturing adjusting the split nuts for wear. > When the threads on the split nut wear... where are the threads > on the screw supposed to go. I think the ideal situation when adjusting > the split nuts would be to have a section of lead screw with cuts in it > and use it like a tap to cut the split nuts threads deeper. I guess I'm theorizing that the half nut will evenly wear down. (Maybe wishful thinking!) I have taken a 5" piece of 3/4 steel and threaded it to 8tpi tapered the tip and cut slots in it like a tap. Chucked the whole mess up in a reversible powered apparatus and was able to experiment with the old half nuts and was able to effectively cut new threads. The brass or bronze should outlast that zinc pot metal (or whatever it is). If the lead screw takes a bit more wear than normal, o well, might beat the constant hassle of foolin with the nuts every 6 months. I guess I can make a lead screw once every 8-10 years. :-) Mark ------- Re: Half nut chaos Posted by: "wa5cabx~xxcs.com" Date: Sat Feb 18, 2012 11:11 pm ((PST)) Acme threads have four surfaces that can wear (root, crest, and leading and trailing sides). Half nuts mostly wear on the side toward the tailstock. If root or crest wears very much, something is either wrong size or out of adjustment. And the side toward the headstock will only wear if the the carriage is routinely backed up under power (not common). Zamack isn't pot metal. And wears better than brass and probably better than bronze. Robert Downs - Houston wa5cab dot com (Web Store) ------- Re: Half nut chaos Posted by: "inspiro_creo" david.deboizex~xxverizon.net Date: Sun Feb 19, 2012 1:46 pm ((PST)) Mark With my previous post, I was thinking exactly what miner49r stated. Not knocking your idea, I still believe it's an excellent build. But I couldn't either see how adjusting the brass half-nut would be re-threaded by the lead-screw. From what I understand most if not all cutting would be done right to left, that meaning that one side of the thread on the half-nut would wear more, making the thread wider, not deeper. All in all, it's still a winner. I still think that when one is set up to make the brass half-nuts, one can make several sets, two, three, etc. and make just one steel holder/slide. As time goes by and the brass nuts wear, you can scrap them and reinstall the next new set. Far better than, like you stated, be a slave to the parts supplier. Here you will always have one spare set available. Then make new ones as needed, still having the original steel holder. Like you, I'm new to this and still getting my 12" lathe in just running/ working condition so I can make some cuts. Later I will concentrate on doing a full restore. However, your design will be in my projects to do first. David ------- Re: Half nut chaos Posted by: "jerdalx~xxsbcglobal.net" Date: Sun Feb 19, 2012 2:15 pm ((PST)) For what it is worth, it is very common, for instance with dividing heads, to have the worm adjusted deeper as wear occurs... While this is not really a "worm" application, it is similar, and uses similar (not identical) "screw" profile and contact geometry as a worm. As I understand the setup from a brief look, that is generally what the OP proposed, and I don't see any particular reason why it wouldn't work. I think it might be good to cut the nut thread a bit deeper than usual, i.e. non-spec. JT ------- half nut trouble shooting A/C 10-12 [atlas_craftsman] Posted by: "oldmekanik" oldmekanikx~xxyahoo.com Date: Fri Feb 24, 2012 1:42 pm ((PST)) I recently set about fixing issues with my half nuts. I got into it pretty deep. My end result should say a lot. My carriage free travel is now 0.0025 to 0.004, the lead screw tail support bearing is 0.002 of that. Threading is beautiful. I ordered a new scroll and half nuts, installed them. The results were not as good as i had hoped for. The scroll was not engaging the half nuts all the way on the lead screw. Careful examination showed that the pins were located 0.030 closer to the lead screw center than needed for complete engagement. That alone is 0.060 of lost contact area, that is 50% of the load bearing area. The pin location varied quite a bit from one set of half nuts to another. I have 5 sets of half nuts. The fix is to relocate the pins. This is easy. Determining how much is a matter of several factors which mean i cannot give you an absolute number. I recommend that you do your test holes on an old set and try them before modifying a new set. The desired result is to get complete engagement of the nuts on the lead screw. On my test nuts i did not bother to use threaded pins, i just used good fitting straight pins after boring the new holes. I will outline steps in the next post. ed ------- half nut trouble shooting A/C 10-12 part 2 Posted by: "oldmekanik" oldmekanikx~xxyahoo.com Date: Fri Feb 24, 2012 2:48 pm ((PST)) Close the half nuts on the leadscrew with an even gap front and back. That should be about 0.0625. 1. Measure the distance from outside of pin to outside of pin. RECORD THIS NUMBER. 2. Measure the scroll grooves in the engagement position outside to outside (that is the 2 ends closest to center). RECORD THIS NUMBER. 3. Subtract #1 from #2. Half this number is the amount of offset you need to move each pin center. RECORD THIS NUMBER. use a 5/16 end mill to bore the offset, as a drill bit will migrate. I set the nuts in the vise with the parting faces together to help prevent getting the centers out of line. Turn some close fitting pins. Assemble the nuts to carrier and fit to leadscrew. If you removed the scroll from the apron you can do a quick trial closure. Look for the same fit that you got when you just held the nuts closed on the screw with your fingers. If still loose, offset more and make shouldered pins. A little tight is ok as parts will wear. When you are satisfied with the fit, start the mod on the new half nuts. Use 1/4 28 stock for the new threaded pins. You don't really need the slots. Factors such as worn scroll shaft and loose carrier to half nut tolerance contribute to more play, but you can add a few thou to the offset to get more closure if you want. I ran 7 combinations of good and worn parts and the results were really telling. Every time i corrected something out of spec things got better. Even made my own new scroll out of brass. (I like it so much that the one i ordered is now a spare.) Enjoy threading as it should be. ------- Re: half nut trouble shooting A/C 10-12 Posted by: "Glenn N" sleykinx~xxcharter.net Date: Sun Feb 26, 2012 5:36 pm ((PST)) So, the new half nuts from Clausing didn't fit right and as a result of the change only the top halves of the threads are wearing off fast. That explains why some people are having to replace halfnuts frequently then. ------- Re: Slipping half nuts/carriage .....video to come [atlas_craftsman] Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Tue Jan 8, 2013 6:35 pm ((PST)) southern_chinook wrote: > Carriage pulled of and it STILL is not obvious to me what's going on. > I see the spring and ball only hold the half nuts open so I don't think > I can blame them. No, that is just to keep the nuts from closing by gravity of the handle. There is a round cam that is operated by the handle to close the nuts. The nuts have pins that ride in arcing slots in the cam. If the cam or pins are worn, then the nuts cannot be held closed on the screw. The pressure of the threads will try to open the nuts, especially when the screw is worn. > I am unsure of which way to assemble the mechanism back together > as I can turn the cam one way and then completely the opposite and > still it functions the same (other than making the lever in a different > position) I wonder if the pin on one of the nuts is completely broken off? Jon ------- Re: Slipping half nuts/carriage .....video to come Posted by: "JOHN PERRY" perry7122x~xxbellsouth.net Date: Tue Jan 8, 2013 6:40 pm ((PST)) Do the half nuts mesh with the lead screw grooves when fitted to them by hand? John ------- Re: Slipping half nuts/carriage .....video to come Posted by: "southern_chinookx~xxyahoo.ca" Date: Tue Jan 8, 2013 6:50 pm ((PST)) "Ken Harrington" wrote: >Before you do too much more, check to see if the groves in the leadscrew may be packed with dirt and old oil. Mine did the same thing when I first got it and it did not look like anything was in the grooves but when I ran a small screwdriver in the grove a lot of garbage came out. Soak the lead screw with penetrating oil overnight, then with it under power feed, run a small screwdriver tip or scratch-all point back and forth in the grove. Oil it again then run a wire brush back and forth on it. That fixed mine. Also make sure that the carriage is not too tight, adjust the gibbs so that they just start to drag slightly, on some opperations you may want them tighter like for milling but in my experience the slight drag is best for lathe work. If it is hard for you to move it is likely too tight for the leadsrew to move. Just my humble opinion of course. On my lathe the half nut lever is disengaged in the up position and engaged in the horizontal position, hope that helps, Ken.< Yes they mesh very well when held on by hand. As far as I can tell...the half nuts are fine, the cam is fine and the lead screw is clean. The half nuts just don't seem to clasp the screw firmly enough. I think I will try new half nuts and a new cam, once again out of desperation. I have on hand used half nuts and a new cam and they look just like what I have in the machine. Maybe my half nuts are bad or more likely, maybe I'm half nuts!! Don ------- Re: Slipping half nuts/carriage .....video to come Posted by: "jerdalx~xxsbcglobal.net" Date: Tue Jan 8, 2013 7:19 pm ((PST)) I would NOT do that yet...... you will have 3 sets, and can only use 1! First, find the problem that allows the movement. It should be rather obvious if you look at the mechanism. As Jon and I said, there are spiral slots that guide the pins on the half nuts up and down. They SHOULD be reasonably snug, without being at all stiff or "grindy". When the nuts are open, the upper nut pin rides on the lower edge of the slot..... when engaged, it is prevented (or should be) from moving up and down by the pin being a good fit in the slot, and both pins being engaged in their respective slots. If it is even halfway right, they should work well, both half nuts should be held in position too close together for the half nuts to skip threads. It should be impossible to move them as far away from each other the way the upper one moves in the video. This is not a particularly precision assembly... the two slots themselves set the distance, along with the pins (and the guides the nuts slide in). The cam plate may be loose on the pins, at least one pin may not be engaged in it, a pin might be missing, the pins could be the wrong diameter (don't fill the slot), the guides could be loose, or there is some other unspecified problem. EVEN IF the nuts were worn, they shouldn't move like that... the lever and cam plate (disc) should control their position even if the threads are bored completely out of the nuts. EVEN IF the plate were the wrong size... with slots too far apart... the nut should not move like that... might not engage the scerw, but the nuts should be fairly snug. Now, the nuts presumably slide in some sort of guide... I don't recall that model well... As I mentioned above, you COULD have a problem with the guide being too loose, and allowing the nut(s) to cock off angle, and then they could skip as the video shows. Maybe someone shimmed it? If there was that much wear, I think you would have commented on it, but... JT ------- Re: Slipping half nuts/carriage .....video to come Posted by: "Ken Harrington" dreamcraftersx~xxmsn.com Date: Tue Jan 8, 2013 10:12 pm ((PST)) southern_chinook wrote: > Maybe my half nuts are bad or more likely, maybe I'm half nuts!! Maybe you're onto something? If you have three sets of half nuts is there a possibility that the sets got mixed up and you have two of the same side? Not sure if the two parts are identical or not they may be different. When you place them on the lead screw like you did to see if they mesh did the straight edges line up perfectly or were they offset slightly? In studying the video I see that the lead screw runs true until you engage the half nuts then it clearly wobbles up and down showing a good deal of pressure is being exerted but the carriage dosen't even budge at all, almost like it is locked in position. In comparing the gap in your carriage lock clamp to my lock clamp gap it appears as though your carriage is locked (OK maybe now I'm half nuts :) ), there realy should be some movement of the carriage if it is adjusted to move freely enough for the lead screw to move it. On this perticular model the half nut cam has two slots that the half nut pins ride in not spiral slots and through trial and error (more error than trial). I have discovered that if there is too much friction in the movement of the carriage the half nuts will skip like shown in your video. Before you put it back together do check for built up crud in the grooves (threads) of the half nuts. After assembling the half nut assembly on the carriage check to see if the nuts are able to close properly (meet together) and check to see if the threads in the nuts mesh with each other (put a piece of playdough or clay in there and close the half nuts, pull the dough out and examine it) if they don't mesh (the threads spiral around like they should) you have a miss-matched set. If you already put it back together try this; with the unit turned off engage the nuts, do they both seat in the lead screw at the same time, if not they are likely miss-matched. If all that checks out I'd be inclined to think it is more an issue with the carriage needing to be freed up. Try setting the carriage a little sloppy and see if the nuts engage? Don't continue to run the half nuts allowing them to skip or it will chew them up. I guess another question might be: are the threads of the lead screw the same all the way across its length or are they rounded off in the middle section? There are spots on the ends that would never see any use so would be a good example of the condition the whole screw should be in. Did you try engaging the carriage in different locations? Anyway there's a few more things to try, don't give up, I can't tell you how many times I have wrestled with something like this only to discover it was something too simple to have considered in the first place. Happy tinkering, Ken ------- Re: Slipping half nuts/carriage .....video to come Posted by: "anthrhodesx~xxaol.com" Date: Tue Jan 8, 2013 10:55 pm ((PST)) Jan 7, 2013 10:12 pm (PST), jerdal writes: > OK, I never have had a 618, never used one..... BUT..... The half nut is moving but the lever is staying still. That suggests to me that the disc which is moved by the lever is not holding the half nut correctly in position. It appears that the half nut is merely falling into position by gravity. There should be in most lathes, some sort of spiral slot in that disc, which moves a peg on the half nut, moving the half nut positively into position. That disc may not be adjusted/positioned right, may not be the right one, or may not even be present on your machine. Some partial fix may have been done at some point with a "homebrew"done at some The half nut should be solidly held in mesh by the slot in the disc holding the peg from moving up and down < Don and JT, The split nuts clearly are not closing on the leadscrew. During the video you can see a gap between the top of the leadscrew and the top half of the split nut. Additionally, the fact that the threading dial gear is rotating tells you that the carriage is not traversing at the same rate as the pitch of the screw. You need to remove the carriage and operate the split nut while you can watch its operation. The operating cam on Atlas split nuts has two simple straight line slots to close the two halves but it is essentially the same operation as with curved slots, just not as sophisticated. Anthony Berkeley, Calif. ------- Re: Slipping half nuts/carriage .....video to come Posted by: "trillium_38" rdgx~xxrobgal.com Date: Wed Jan 9, 2013 12:42 pm ((PST)) Don, A couple of things to check: 1) the two half-nuts in a pair are different - one should be marked with a "1" and the other with a "2". The threads in the two halves are offset from each other (relative to the edges sliding in the slot) by a half revolution of the leadscrew. If you have two #1's or two #2's instead of a true pair, that could prevent both halves of the nut from seating properly on the leadscrew and might be the cause of the problem you are seeing. Question to all -- does anyone know which half, #1 or #2, should be uppermost? As far as I can see it shouldn't really make any difference since the thread dial indications are relative not absolute. 2) check that the pins in the two halves of the nut are tight and perpendicular to the back face. I had a case where one half-nut had a small defect (bubble) in the zamak casting at the position where the pin was fitted, allowing the pin to become loose and tilt. This resulted in behaviour quite similar to what you are seeing. Good luck! Robert ------- Re: Slipping half nuts/carriage .....video to come Posted by: wa5cabx~xxcs.com Date: Wed Jan 9, 2013 12:47 pm ((PST)) Don, none of your photos show a view of the flat base of the half nuts, or of the threads. So we can't see the condition of the actuating pins and threads. It might help to add that. The disk with shaft with the two slots across the face of the disk is called the scroll (which I know doesn't make a lot of sense on a 6" as the slots are straight). Your photo titled "Half Nut Cam" seems to show the end of the actuating lever just visible past the threading dial gear. If the lever will only go on the shaft one way, then that should be the correct closed position for the scroll. What I would do is to block up the apron as in photo "Half Nut Cam" such that you can operate the lever. Set the two half nuts down on the scroll. Set the retaining plate on the apron and install the two screws finger tight. Operate the lever to open and close the halfnuts and with the lever in the closed position, see whether you can pry the half nuts apart as much as they appeared to move in the photo. See how much in general you can wiggle the half nuts around. Remove the screws and retaining plate, lay the lead screw across the apron, close the half nuts on it and reinstall the retaining plate and screws. Repeat the prying and wiggling. Robert D. ------- Re: Slipping half nuts/carriage .....video to come Posted by: "c_h_a_r_t_n_y" mgibsonx~xxstny.rr.com Date: Wed Jan 9, 2013 1:27 pm ((PST)) I might ask to add on. The lever should be 45 degrees up from horizontal in the open position, and 10 degrees down from horizontal in the close position. Both half nuts should be ~3/16 clear of the lead screw when open, and visible from the tail end. When closed, they should be very close together. If not you need to take the carriage off and see what is wrong. The lever is on the scroll shaft with a square. If it has ever been off, it could be put back wrong. I took mine off and cleaned it and put it back. I took a pic and marked the scroll as to up so I did not miss the index and really mess it up. To keep my lever on I drilled and tapped #6 and used a screw and washer to hold it on. Original was bradded. I have a spare carriage I got off ebay with half nuts and scroll. The half nuts were misformed. One had the steel shaft in crooked and is not usable. It could not have been bent. Day one fail. There are 2 different types of half nuts used on 6". One is just longer than the other and has a different "guides". And my book calls the scroll a "cam". And the half nuts were $1.60 a pair in 1972. chart [later message] Add on: 6" half nuts are either half inch long or 3/4" long and the guide plate must match the size. There must be #1 and #2 half nuts for a pair, and which goes on top/bottom does not matter. ------- Re: Slipping half nuts/carriage .....video to come Posted by: wa5cabx~xxcs.com Date: Wed Jan 9, 2013 2:08 pm ((PST)) chart, I agree that "cam" makes more sense. For some reason in the 6" parts lists, it's a cam, and in the 9", 10" and 12" it's a scroll. Around 1960 or so, a pair of 6" halfnuts cost 75 cents. ------- Re: Slipping half nuts/carriage .....video to come Posted by: "Jon Elson" elsonx~xxpico-systems.com Date: Wed Jan 9, 2013 5:53 pm ((PST)) trillium_38 wrote: > Question to all -- does anyone know which half, #1 or #2, should be uppermost? As far as I can see it shouldn't really make any difference since the thread dial indications are relative not absolute. < No, I think it would make a difference. If you put them in "right" the marks on the thread dial will line up when engaged. If you flip the half nuts, then I think the marks would be half a thread off. Jon ------- Re: Slipping half nuts/carriage .....video Posted by: "mtltinker" davelj6x~xxmsn.com Date: Wed Jan 9, 2013 1:21 pm ((PST)) I would remove the Split-nut Guide, Atlas part #M6-13 and check with a straight edge, if that part has any bend it will allow the split nuts to move and disengage from the lead screw. ------- Re: Slipping half nuts/carriage .....latest update. Posted by: "southern_chinook" southern_chinookx~xxyahoo.ca Date: Wed Jan 9, 2013 1:48 pm ((PST)) Wow, what should have been a small little fix, has turned out to be more involved than what I would have guessed! Thank you so much to everyone for all of their suggestions and help. Well it turns out I did have two of the same half nuts installed...at least since one of my previous assembly/dis-assemblies. So I fixed that and that made things better but still not right. So I proceeded to install a new cam/scroll. I made a couple more videos that will help explain the situation. http://www.youtube.com/watch?v=sb3XdcRzBq4 While the new cam definitely made things a lot tighter and better I am not convinced I have it together right yet or that my half nuts may be flaky. http://www.youtube.com/watch?v=TwFmcyxGF48 Having never owned or operated another lathe before it's hard for me to know what the correct feel of the lever engagemnet should be like but I don't think it is right yet. It seems I could only assemble the new cam in the carriage one way (with only one of the scroll slots pointing upward as in parts diagram). I think I will go and try an umpteenth time to do it different. I see that same guy that always has a bunch of 618 parts for sale on eBay has new half nuts for sale at damn near $60 a pair plus shipping!!! Should have stocked up on them in 1972! (but I was only 3 years old then!) Don ------- Re: Slipping half nuts/carriage Posted by: "Jim Peterson" f4d711x~xxaol.com Date: Thu Jan 10, 2013 1:30 pm ((PST)) I bought a pair of new half nuts (M6-12A) and the matching guide (M6-13A) from Clausing in June 2011. The half nuts were $36.48 and the guide was $3.28, for a total of $39.76. Shipping was $8.98, for a grand total of $48.74. These were the latest version of the half nuts and guide and solved my feeding problems on my 618 lathe. Your 2nd video looks like pretty normal operation of the half nuts to me. The feed screw has to rotate until it meshes with the half nuts and so it feels "stiff". Good luck! Jim Peterson ------- Re: Slipping half nuts/carriage Posted by: "southern_chinook" southern_chinookx~xxyahoo.ca Date: Thu Jan 10, 2013 4:51 pm ((PST)) Thanks Jim, That is exactly what I am going to do also...buy both half nuts and the guide. If that doesn't fix things I will be at a loss! Don ------- Re: Slipping half nuts/carriage Posted by: "Guenther Paul" paulguenterx~xxatt.net Date: Thu Jan 10, 2013 1:45 pm ((PST)) Jim. Couldn't you make your own nuts from bronze? They would last you forever. I believe the instructions are in the files. GP ------- Re: Slipping half nuts/carriage Posted by: jerdalx~xxsbcglobal.net jtiers Date: Thu Jan 10, 2013 6:01 pm ((PST)) OK, I looked at the other two videos... and reviewed the original one. I notice that whatever you changed (cam? half nuts?) allows the half nut lever to move a bit farther, presumably making the nuts more positively engaged. However, it did look as if the engagement was decent on the first video, but the halfnut was allowed to jump out of the threads by some fault in the holding system. There is some remnant of that behavior still present. The half nuts should not pop up and stop the feed from a little pressure on the handwheel... You may have noticed the comments here a while back concerning breakaway leadscrew bearings... those were apparently designed and intended to break before something else if the carriage was jammed... Very good evidence that the halfnuts in general are pretty solid on most lathes, even other Atlas models, so presumably on yours they should be as well. Before willy-nilly ordering a lot of new parts, you may want to look and see if the nuts and/or guides are worn enough or loose enough to cause your problem, and if they are, see if you can identify the reason. The cam didn't look trashed, so it seems odd that the parts that the cam moves would be a lot worse than the cam. Of course it might have been replaced.... or the sum of the not-very-obvious wear on the cam plus nuts plus guides is enough to be a problem. That's possible, of course, and if it is, replacement is a good option. You might want to convince yourself that it really IS the issue, before replacing parts like an auto technician... "to see if that was the problem". The "customer" will be paying, naturally... whether the parts are needed or not. I'd start by closing the half nuts with the apron off the carriage... and wiggling them to see if they are loose... If they ARE loose, seeing what about them is loose, i.e. the pin, the part that goes in the guide, perhaps the guide itself... maybe the slot in the cam. When you find the real problem, you will also know the real fix for it. JT ------- Re: Slipping half nuts/carriage .....video to come Posted by: "trillium_38" rdgx~xxrobgal.com Date: Fri Jan 11, 2013 10:30 am ((PST)) Jon: Yes, I agree that you are correct that reversing the #1 and #2 half nuts would result in some change in the thread dial indicator alignment when the nuts are engaged, making the lines not 'line up' exactly the same for "#1 on top" and "#2 on top" configurations. However the change in alignment is small enough, (1/64th. of a revolution of the thread indicator dial, equivalent to a half-revolution of the leadscrew driving the 32-tooth gear), that on a 5/8" diameter dial it's not much more than the thickness of the scribed lines. Since thread pickup is based on dial markings at 180, 90, or sometimes 45, degree intervals, there would be no danger of ambiguity in choice of line to pickup on. So from a practical standpoint I don't think it matters which half nut is uppermost, but if one desired to have precise alignment of the dial and reference scribe marks during engagement, one could always shim the thread indicator assembly relative to the carriage to achieve that. Robert ------- Re: Slipping half nuts/carriage .....video to come Posted by: wa5cabx~xxcs.com Date: Fri Jan 11, 2013 4:49 pm ((PST)) One thing that I was going to add to this is that I learned years ago that even for general machining if you use the threading dial as an indicator you can always snap the half-nut lever down smartly at the instant that the nuts will easily engage with the lead screw threads. I use the #1 indicator line normally. Robert D. ------- Re: Slipping half nuts/carriage .....video to come Posted by: "c_h_a_r_t_n_y" mgibsonx~xxstny.rr.com Date: Fri Jan 11, 2013 5:40 pm ((PST)) To each their own devices. I removed my threading dial and stored it some time ago. I use motor reverse and do not dis-engage the half nut lever until I am done threading. Since I use variable speed I just slow down to the end of the cut, back out, reverse and speed up for rapid revese, slow down to do the next cut. Saves time and potential error in engagement. Just my take. char ------- Re: Slipping half nuts/carriage .....video to come Posted by: wa5cabx~xxcs.com Date: Fri Jan 11, 2013 8:20 pm ((PST)) Well, different strokes... I wasn't referring to threading work. And reversing to get back to the start of a cut just doubles the machine wear. ------- Re: Slipping half nuts/carriage .....video to come Posted by: "Carvel Webb" carvelwx~xxabsamail.co.za Date: Fri Jan 11, 2013 11:29 pm ((PST)) HI Robert: As you say - different strokes . As most of the threading I do for my stuff is Metric, one does not have a choice other than to keep the half nuts engaged where a metric conversion has been used on an Imperial machine (or vice versa). There is also a school of thought that with a machine that has seen some use/wear, the maximum accuracy can be obtained with a cut thread by leaving the half nuts engaged and reversing, thereby eliminating some of the variables. Keep well, and all the best for 2013 Carvel ------- Re: Slipping half nuts/carriage .....video to come Posted by: anthrhodesx~xxaol.com Date: Fri Jan 11, 2013 11:23 pm ((PST)) Jan 11, 2013 trillium_38 writes: > Yes, I agree that you are correct that reversing the #1 and #2 half nuts would result in some change in the thread dial indicator alignment when the nuts are engaged, making the lines not 'line up' exactly the same for "#1 on top" and "#2 on top" configurations. < Robert and Jon, Actually, this is not inherently true. If the split nuts were carefully designed and manufactured so that the offset of the thread at the right end of #1 was the same as the offset of the thread at the left end of #2, and obviously the same for the other ends of each, also the locations of the pins on the back side of each, they could be installed with #1 up and #2 down, or vice versa, or even with two #1s or two #2s, and in each case the result would be the same. It does require thinking of the issue and actualizing it, but in fact it would be good design. I haven't studied the split nuts to determine whether they went to the trouble or not. Anthony Berkeley, Calif. ------- Re: Slipping half nuts/carriage ....problem solved, I think Posted by: "southern_chinook" southern_chinookx~xxyahoo.ca Date: Sat Jan 26, 2013 9:23 am ((PST)) Okay, Finally, I replaced the half nuts with a brand new set and a brand new scroll/cam was installed. The lathe appears to work ok now. I am pretty sure the old scroll/cam was fine (but I thought that about the half nuts too). Only with very careful examination and comparison with the new ones could I see that the old half nuts had wear on them. I posted a couple of comparison pictures in my album "My New Old Atlas 618". Interestingly enough, the new half nuts from Clausing are identical to each other and no longer are identified as 1 and 2. Both are labeled as 1. ------- Re: Slipping half nuts/carriage ....problem solved, I t... Posted by: wa5cabx~xxcs.com Date: Sat Jan 26, 2013 10:36 am ((PST)) I've called Clausing three times (on other matters) and each time asked for an "official" statement that the "1" or "2" on each part. (I bought a 12" set and they are both 2's and look OK when held on the leadscrew except for a slight horizontal offset between the two tapped holes) no longer matters. I'm still waiting for the statement. Robert Downs Houston ------- Thread dial indicator [myfordlathes] Posted by: "haydut1200" haydut1200x~xxgmail.com Date: Wed May 15, 2013 9:33 am ((PDT)) I've never needed to cut a thread on my lathe, but decided it's time I had a go. First thing I noticed is that the carriage lever won't engage directly on a number. It engages either side, but which is the correct one? Is it possible the indicator has somehow got out of alignment. Martin ------- Re: Thread dial indicator Posted by: "Mike Crossfield" miked.crossfieldx~xxbtinternet.com Date: Wed May 15, 2013 9:37 am ((PDT)) Martin: Sounds like it needs setting up. Add or remove spacing washers between the indicator and the carriage (on mounting screw) until the marks line up. Mike ------- Re: Thread dial indicator Posted by: "Haydut1200" haydut1200x~xxgmail.com Date: Wed May 15, 2013 9:46 am ((PDT)) Thanks, Mike. Job done, an extra washer was all it took. Aren't things simple when you know how? :) Martin ------- Re: Thread dial indicator [atlas618lathe] Posted by: "azbruno" azbrunox~xxyahoo.com Date: Wed May 15, 2013 8:49 am ((PDT)) wa5cab wrote: > The gear is a press fit on the shaft. I wouldn't take it apart unless I > had to replace the gear. If it turns freely now, I would just lube it > per the lube chart (Weekly). A warning for if you take apart a thread dial... you need to be accurate in getting the dial aligned when putting it back together, otherwise the engagement of the half-nut might not occur spot on the line of the dial. I haven't taken one apart myself, but I do have a few dials and one of them is a bit off. I once had to clean one by soaking in kerosene and then using an air compressor to blow out everything I could before lubing it. Bruno ------- Re: Thread dial indicator Posted by: "Curt Wuollet" wideopen1x~xxcharter.net Date: Wed May 15, 2013 7:29 pm ((PDT)) The one I just bought was stuck and probably had been for ages. It had a casting with a smaller diameter opening than the dial so there was a crescent shaped opening and that was fill of copper flakes. Every time I thought I had it free, another flake would get trapped in the end of the crescent. I think they are all out now. I'm just going to leave it engaged for a while to keep it free. Regards cww ------- Re: Thread dial indicator Posted by: wa5cabx~xxcs.com Date: Wed May 15, 2013 10:15 pm ((PDT)) My threading dial has been engaged for the past 32 years. I use it every time that I engage the half nuts. Much easier on both the half nuts and the lead screw. Robert D. ------- Re: Thread dial indicator Posted by: "Leo Reed" lpreedzonex~xxearthlink.net Date: Thu May 16, 2013 10:53 am ((PDT)) A bit of caution, do not overtighten the bolt that holds the threading dial indicator. This can cause the shaft to bind. Leo (pearland, tx) ------- Atlas 6 inch half nut [atlas_craftsman] Posted by: felix8470x~xxcomcast.net tallgitawr Date: Wed Jul 30, 2014 8:30 am ((PDT)) I am slowly working my way through reviving this Atlas 6 inch lathe, and am stumped with an issue with the half nut. The half nut lever will not engage at the far left and far right of the carriages travel. But if the half nut is engaged in the middle of the lathe bed, I can see the lead screw move up about 1/8 inch. I peeked in the left side of the carriage, and can see the half nut action, and the bottom half nut engages first, pushing the lead screw up, altho the top half nut does engage, but after the bottom nut. In other words,the half nut engages and seems to work fine in the middle of the carriages travel, except for the fact that the lead screw is bent upward. And since the lead screw is held firmly in place at it's ends, the half nut wont engage at the ends of the lead screw travel. Something's not right, and I hope there is a slim chance I won't have to remove the carriage to fix this. Thanks in advance for your help Felix ------- Re: Atlas 6 inch half nut Posted by: "JACK SIMS" jack-br549x~xxatt.net Date: Wed Jul 30, 2014 9:32 am ((PDT)) Sounds like you might need a new lead screw. If you can't get yours to run straight. Jack ------- Re: Atlas 6 inch half nut Posted by: felix8470x~xxcomcast.net tallgitawr Date: Wed Jul 30, 2014 9:44 am ((PDT)) The lead screw is perfectly straight, until I engage the half nut. And it springs back to normal when I release the half nut lever. ------- Re: Atlas 6 inch half nut Posted by: "James Irwin" jirwin1x~xxaustin.rr.com jimirwin2001 Date: Wed Jul 30, 2014 9:54 am ((PDT)) Remove half-nuts Remove chips embedded therein Reassemble Batcha will see better results! Jim I ------- Re: Atlas 6 inch half nut Posted by: "Jon Elson" elsonx~xxpico-systems.com jmelson2 Date: Wed Jul 30, 2014 10:10 am ((PDT)) That means either the apron is not at the original height due to bed wear and maybe regrinding of the bed, or the cam and half nuts are worn in such a way they are leaning unevenly on the screw. Jon ------- Re: Atlas 6 inch half nut Posted by: wa5cabx~xxcs.com wa5cab Date: Wed Jul 30, 2014 5:52 pm ((PDT)) Felix, If swarf (shavings) stuck in the lower half nut isn't the culprit, either the carriage is too high (bed and/or carriage wear would lower it, not raise it) or the lead screw is too low. You can (usually) fix the problem at the right end by running the carriage all the way to the right, loosening the two cap screws holding the right bearing housing, closing the half nuts (which will raise the lead screw and bearing) and tightening the cap screws securely. I'm not familiar enough with the 618 to know whether you can do the same thing at the headstock end or not. You might have to shim that end. In any case, before you close the half nuts at that end, loosen the banjo (change gear quadrant) and swing it down, disengaging the A-position gear from the tumbler compound gear. Robert Downs - Houston wa5cab dot com (Web Store) MVPA 9480 ------- Re: Atlas 6 inch half nut Posted by: "brokenwrench1 ." brokenwrenchx~xxgmail.com Date: Wed Jul 30, 2014 11:30 pm ((PDT)) I had the same thing happen and my lead screw bushing hanger was worn out on the tailstock end. A good used lead screw and half nuts made from brass are available on ebay at reasonable prices. You can buy an entire 618 in pieces if you want to. ------- half nut success - sort of. Posted by: felix8470x~xxcomcast.net tallgitawr Date: Wed Jul 30, 2014 4:51 pm ((PDT)) I took the apron off, and as suggested, the half nut threads were full of gunk. Also, the cam with two slots that engages the half nut was also really packed with gunk in the slots. After cleaning and reassembly, it now works much better - altho the lead screw still moves upward, about 1/16 inch when the half nut is engaged. But since it seems to work OK without binding, I am going to move on to the next stage of the job - mounting a motor and wiring. But, can a few owners of the Atlas 6 inch verify what their lead screw does (if anything) when they engage the half nut? Again, thanks for ideas. Felix ------- Half nut problem solved Posted by: felix8470x~xxcomcast.net tallgitawr Date: Thu Jul 31, 2014 10:24 am ((PDT)) Thanks for advice. It turns out, that the hanger on the tail stock end was worn, and also, I had to remove a lot of shavings and dry, hard grease in the half nut mechanism. I have a "parts" lathe, and swapped hangers and now the problem is gone. ------- Suggestions for a sticky threading dial [atlas618lathe] Posted by: "Pat/Juke/Whatever..." chefjukex~xxchefjuke.com ChefJuke Date: Tue Feb 24, 2015 8:00 am ((PST)) Hi all, Newbie here, in the process of refurbishing a Craftsman 101.21400 lathe. Came across an interesting problem. The threading dial on this machine initially barely did not turn, or, more accurately, turned only with significant force applied. Soaked for a bit in parts cleaner and then it helped ever so slightly. Seemed to have some significant gunk inside (mummified grease?). I couldn't see a way to disassemble it to get at the guts and noted that there is very little gaps to allow solvent get into the body of the thing. Finally had the idea of heating it up and when I did, it moved MUCH more freely, but tightened up once I cooled it down again. Not as tight as it was before, but still a little tighter than I would like. So, looking for suggestions on what to try next. I can heat it for longer and see if whatever seems to be gunking it up inside can either burn or melt off or try to disassemble or... Any suggestions appreciated. Chef Juke www.chefjuke.com ------- Re: Suggestions for a sticky threading dial Posted by: egpacex~xxhotmail.com egpace Date: Tue Feb 24, 2015 8:47 am ((PST)) Parts cleaner is a solvent and will dry out quickly. I'd try soaking it in Kroil penetrating oil or a 50-50 mixture of automatic trans fluid & acetone. Good luck, Ed ------- Re: Suggestions for a sticky threading dial Posted by: "Pat/Juke/Whatever..." chefjukex~xxchefjuke.com ChefJuke Date: Tue Feb 24, 2015 9:42 am ((PST)) Ed, Thanks. It just so happens I have it soaking in Kroil right now. Figured I'd give it a day in Kroil and see how it comes out. Thanks, Chef Juke ------- Re: Suggestions for a sticky threading dial Posted by: "Lost helm" losthelm1x~xxyahoo.com losthelm1 Date: Tue Feb 24, 2015 10:32 am ((PST)) I have had similar issues with old farm equipment. If you can submerge the part and let it soak, work the articulation when you're able and try to flush out all The old grease. Be careful with heat and solvents. Most have a low flashpoint and you get odd looks until the eyebrows grow back. ------- Re: Suggestions for a sticky threading dial Posted by: "John Williams" grain914x~xxsuddenlink.net Date: Tue Feb 24, 2015 11:28 am ((PST)) I would warm (not hot enough to be in danger of causing a fire) and then soak it in a 50/50 mixture of automatic transmission fluid and acetone. Grain914 ------- Re: Suggestions for a sticky threading dial Posted by: zoyagenax~xxyahoo.com gennady_123 Date: Tue Feb 24, 2015 12:00 pm ((PST)) I had the same problem when I bought my 618. Tried different things, but ended up with disassembly and cleaning. The dial is mounted on the shaft by press fit, so I just carefully use the punch while supporting the body in the vise. Then I mounted it back, engaged half nuts align the marks on the dial and body and press the dial back carefully using big pliers (or C-clamp, do not remember now). It is just the description what worked for me, not the guaranteed recommendation. It is your choice what to do. Good luck, Gennady ------- Re: Suggestions for a sticky threading dial Posted by: "Pat/Juke/Whatever..." chefjukex~xxchefjuke.com ChefJuke Date: Tue Feb 24, 2015 3:50 pm ((PST)) Hi Gennady, That is really helpful. I wasn't sure if it was pressfit and the parts diagram didn't give me much to go on. I didn't want to try and pull it apart if it was going to damage it. I will see how the soaking in Kroil does and if it still need more cleaning, I'll carefully disassemble. Cheers, Chef Juke ------- Re: Suggestions for a sticky threading dial Posted by: wa5cabx~xxcs.com wa5cab Date: Tue Feb 24, 2015 7:18 pm ((PST)) Pat, Both the gear and the dial are pressed onto the shaft. Robert Downs - Houston ------- Re: Suggestions for a sticky threading dial Posted by: "Pat/Juke/Whatever..." chefjukex~xxchefjuke.com ChefJuke Date: Wed Feb 25, 2015 8:18 am ((PST)) Okay, so once the fact that this was press-fit was revealed to me, this was simple: Disassembled, cleaned the shaft and interior of the dried up gunk, and all is well with the world. Thanks for the info/advice! Cheers, Chef Juke ------- Backlash [atlas_craftsman] Posted by: tpmurconx~xxyahoo.com tpmurcon Date: Mon Aug 10, 2015 1:13 pm ((PDT)) I have discovered possibly a problem with my 10f. Can anyone tell me how much play should I have on my feed screw when the half nuts are engaged. Mine has a total of .044 thousands, This seems a bit much and it seems to be getting harder to engage. But I have never changed out the half nuts. Is it time to do so? The feed screw looks almost brand new, even though I know it is the original. Should I try tightening the half nuts first? If so How does one go about tightening the nuts. Thanks for any input. Tom ------- Re: Backlash Posted by: "Jon Elson" elsonx~xxpico-systems.com jmelson2 Date: Mon Aug 10, 2015 5:52 pm ((PDT)) That is probably a reasonable amount of backlash. The nut halves have some clearance to the leadscrew, the leadscrew has some clearance on the end bearing, the nuts have clearance into their slots, and that all adds up. First, you want to clean the leadscrew every once in a while. I take a rag, oil it and shove it into the screw with a screwdriver, while the screw is turning slowly. Just ride the rag down the thread until there is too much swarf on the rag, then start with a clean spot of the rag and continue. Then, you have to pull the apron to get the half nuts off, and pick the chips and grunge out of the threads in them. When you put it all back together, it likely will work better, as the nut halves can seat deeper into the leadscrew thread. As far as I know, there is no adjustment of the halfnuts on the Atlas. But, accumulated swarf will prevent them from fully closing on the screw. Jon ------- Re: Backlash Posted by: wa5cabx~xxcs.com wa5cab Date: Tue Aug 11, 2015 9:06 am ((PDT)) Tom, Unless your half nut lever is peened on AND you intend to remove the scroll, you do not actually have to remove the apron from the carriage in order to remove the half nuts. You already apparently have the lead screw removed. Remove the tailstock and crank the carriage off the end of the bed far enough to give access to the 9-13 half nut guide. You may need to loosen all of the carriage gib screws first. Study the exploded view in your parts manual before proceeding. Don't remove the lever. Remove the two 1/4"-20 Fillister Head Cap Screws. Pull the guide and half nuts off the back of the apron. A sharpened putty knife may be useful for getting it started. If you do need to remove the scroll, first remove the 1/4"-20 slotted set screw from the hole above the lever so that the detent ball doesn't pop out and disappear when you remove the handle. Robert Downs - Houston ------- Re: Backlash Posted by: "Carvel Webb" carvelwx~xxabsamail.co.za cwlathes Date: Tue Aug 11, 2015 9:16 am ((PDT)) Tom, just a tip for a “thread pick”. Use a piece of 3mm or so brazing rod about 6 – 8” long –- loop one end into a ‘handle’, and grind the other end roughly into a thread form –- either straight, or with a right angle kink. Also useful for cleaning chuck threads. Regards, Carvel ------- Re: Backlash Posted by: "Thomas Powell" tpmurconx~xxyahoo.com tpmurcon Date: Tue Aug 11, 2015 2:54 pm ((PDT)) Robert, Your knowledge with Atlas lathes sometimes frightens me. I read and try to keep up with all you say and recommend to everyone and try to keep notes. I cannot believe just how dirty it was to clean so I went ahead and pulled the apron anyways. The split nuts look pretty good, a lot of wear on the ends which I expected. I have a lathe parts book but it is so flimsy I am afraid to use it. Do you know where to find a download for it? I started this project last December and I have a lot to learn about my atlas lathe. Thanks again guys for all your help. Carvel, I thank you for the suggestion. I have tried the rod trick before and it does work, however this time I felt everything needed cleaning. Thanks, Tom ------- Re: Backlash Posted by: wa5cabx~xxcs.com wa5cab Date: Tue Aug 11, 2015 9:07 pm ((PDT)) Tom, Thanks for the kudos. With the exception of the 936...954 and the 10A through 10D, the 101.07300, and most of the early 12", there is I think at least one parts manual for every other model lathe that Atlas built to be found in the atlas_craftsman Group's Files section. Log into the Group on Yahoo. Go to Files. Click on the Actions tab and select Alphabetical. Find and click on Manuals, Atlas and Atlas-Craftsman Lathes. Again set sort to Alphabetical and scan the list for your model. In the unlikely event that you don't find your exact model, let me know what your model number is and I will suggest a substitute that will be at least partially correct, and tell you what will be different. Robert Downs - Houston wa5cab dot com (Web Store) MVPA 9480 ------- Half nut woes [atlas618lathe] Posted by: "Carlos Akin" carlosakinx~xxyahoo.com carlosakin Date: Fri Jan 29, 2016 7:41 am ((PST)) Hi Group, What does everyone do when trying to dial in the half nuts? Mine are slipping in the area of the lead screw that is most worn - as usual, but the threads on the half nuts themselves are also half gone. I received a nice used lead screw that has more pointy threads, but has a consistent diameter through its entire length, it does seem to engage better. When watching the half nuts engage, I notice the lead screw moves up a bit as they are closed. Is there some way of adjusting the lead screw so that it doesn't move, and therefore has more consistent engagement? Now I also just received a set of 1/2" wide half nuts that may engage better, but I want to eliminate the stress on them by dialing this in. I am only fiddling with this because I'd like to eventually be able to make my own half nuts if they wear out again. Worst case, I`ll be ordering a new lead screw and half nuts. Thanks! ------- Re: Half nut woes Posted by: "Hank Riley" n1ltvx~xxyahoo.com n1ltv Date: Fri Jan 29, 2016 2:05 pm ((PST)) [posted by moderator for Robert Downs] Carlos, There is no adjustment on the height of the half nuts. What you do is adjust the height of the lead screw. To do this, move the tailstock all the way to the right. Crank the carriage toward the tailstock as far as you can without the carriage touching either the tailstock of the right lead screw bearing. Loosen the two screws attaching the bearing to the bed. Close the half nuts completely (you might need to jocky the carriage back to the left a little to do this –- don’t force the closure). Lift up on the bearing and note how far it moves (if any). Lower it half the movement distance and tighten its mounting screws. Move the carriage to the headstock end of the bed. Open the change gear cover and lower the change gear bracket. Repeat the previous steps with the left bearing. Move the carriage to the center of the bed and close the half nuts. The lead screw shouldn’t move. If it does, it may be bent. If it moves down, you may have considerable bed wear in the middle (not common). If it moves up, the bed may be arched up (again not common). Robert D. ------- Re: Half nut woes Posted by: n1ltvx~xxyahoo.com n1ltv Date: Fri Jan 29, 2016 8:20 pm ((PST)) [posted for Carlos, carlosakinx~xxyahoo.com] Robert, Thank you for this detailed info. I will do this. ------- Re: Half nut woes Posted by: "Carlos Akin" carlosakinx~xxyahoo.com carlosakin Date: Fri Jan 29, 2016 8:22 pm ((PST)) Well, That was an excellent fix. Is this some sort of common knowledge I should get from a manual somewhere, or just your personal method for getting that setup dialed in? It's almost like a new lathe now! Now I can get back to making a delrin tumbler gear to get the noise down. Thanks! ------- Re: Half nut woes Posted by: wa5cabx~xxcs.com wa5cab Date: Sat Jan 30, 2016 3:28 pm ((PST)) Glad to hear that it helped. Unfortunately, Atlas never seems to have published a real maintenance manual for any of its machines. The Manual of Lathe Operations (MOLO, and a book that every Atlas owner should probably have a copy of) included a lubrication chart, in the early editions the instructions for adjusting babbit bearings (for early 10" and 12") and in later editions the instructions for disassembling and assembling the late 12" headstock. Otherwise, the various MOLO versions are all about operations. Later Atlas (by then changed to Clausing) published Technical Bulletins on the various headstocks. Otherwise just parts lists and some setup bulletins. Someone on one of the other Groups wrote briefly how to adjust the right bearing. I just added details so that someone who was relatively new to the machine could more easily follow. And I added the left bearing which only applies to the three 6" models. ------- ------------------------------------------------------------------ This is just one of some 80 files about machining and metalworking and useful workshop subjects that can be read at: http://www.janellestudio.com/metal/index.html ------------------------------------------------------------------