Parting off metal objects (being turned on a metal lathe) looks like it should be easy, but the conversations here try to answer many problems that are typically encountered by new machinists. Find other ideas and tips in the file here called "Cut or Saw Metal". 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 more than 70 additional files on my home page Machining and Metalworking at Home http://www.janellestudio.com/metal/ 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. If you do not have those most recent official instructions, acquire a copy through the manufacturer before operating or using their product. Where the company no longer exists, use the appropriate news or user group to locate an official copy. Be careful -- original instructions may not meet current safety standards. Updated safety information and operating instructions may also be available through a local club, a local professional in the trade, a local business, or an appropriate government agency. In every case, use your common sense before beginning or taking the next step; and do not proceed if you have any questions or doubts about any procedure, or the safety of any procedure. Follow all laws and codes, and employ certified or licenced professionals as required by those laws or codes. Hazardous tasks beyond your competence or expertise should also be contracted to professionals. Let's be really careful out there. (c) Copyright 2003 - 2008 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: Sat, 31 Mar 2001 01:15:34 EST From: LADDERBARx~xxaol.com Subject: PARTING TROUBLE I'm having a problem parting off on my 12 late model atlas. The parts are less than satisfactory and if I I use an insert tool it will brake. Here's a run down I have a phase 2 quick change tool post, the tool bit was aligned with the chuck (square) with minimal tool sticking out. The tool was aligned with a center in the chuck on center, then about .025 above. The saddle has about .002 clearance from the bed and every thing else seems tight. When parting I lock the saddle down and hand feed the carriage. I've slowed the rpm's, used cutting fluid tried soaking the part with WD 40 but I'm still having problems. I hope what I've written makes sense any help in this matter would really be appreciated (and save me some money). Happy Chip Making Mike ------- Date: Sat, 31 Mar 2001 04:41:18 -0500 From: "Dr. Robert Harms" Subject: Re: PARTING TROUBLE The standard parting tool size that fits the Phase II defualt parting tool holder is too small and light weight for any type of work beyond the thinnest aluminum. I bought an Armstrong cut off tool and modified it to fit in the normal tool holder. Works much better ------- Date: Sat, 31 Mar 2001 07:13:55 -0600 From: "Dana Zimmerman" Subject: RE: PARTING TROUBLE The best thing you can do for parting is turn the tool upside down. Seriously. Most lathe operations have an inherent engineering problem, in that the cutting forces tend to flex the tool and tool post down and forward into the work piece. This is especially bad for parting, which is a grabby kind of cut and tool. This strategy also reduces the very real danger in parting. The wisest machinists with the "modern" lathes that have a cross slide that is long enough, put the parting tool behind the work piece and upside down. In this arrangement, when the tool grabs, the tool post flexes away from the work, and releases the pressure on the tool rather than making it worse. It will work with the tool in front of the work, but in this case you have to turn the lathe "backward" which could unscrew the darn chuck. My father apprenticed as a machinist in the 1920's and has told me that when he started out, every machine shop had a couple of guys with eye patches in the manner of Long John Silver. The cause was usually the parting tool. When a parting tool grabs, and the tool post flexes, the tool digs in and if the lathe has the power, the tool will break in such a way that it sends a triangle of high-speed steel, at high speed, exactly at the right angle to get the machinist leaning over the lathe in the eye. Wear your safety glasses! ------- Date: Sat, 31 Mar 2001 06:20:49 -0800 From: "Larry Bailey" Subject: Re: PARTING TROUBLE I read the other replies. Good advice. In my limited experience I have found that the tool should be right on center. If the tool digs in a little, it will decrease engagement with the work instead of increase it. I also usually part with the power feed. Seems to be smoother than I can hand feed it. Good luck, Larry ------- Date: Sat, 31 Mar 2001 15:45:13 -0000 From: STYSx~xxMINDSPRING.COM Subject: Source codes & advice on cut-offs Larry, I have a document on my home computer that has source codes for Craftsman items. I found it on the internet last year. Email me at stysx~xxmindspring.com, and I'll email it to you if you still need it. Also, my machinist friend taught me that when you are using a cut-off tool, try to use one narrower than the groove you are trying to create. That way you can make multiple plunging cuts, moving your tool left or right between plunges, and not have the material grab on the sides of the tool and cause a crash. I have used his advice with my Phase II holder and with my lantern type holder without any problems in grooving cold rolled steel, bronze and aluminum. I also make it a practice not to cut all the way through with the cutoff tool when I'm making an item like a thrust washer. The last bit before it breaks through, I'll use my hack saw. Wilford always tells me to play it safe, take the time and use the saw! My friend still has both eyes, and all of his fingers (minus the end of one thumb, and he has been a machinist for close to 40 years! Hope this helps Rick Stys Apex NC Craftsman/Atlas 12X24 ------- Date: Sat, 31 Mar 2001 13:40:08 -0500 From: Jude Miller Subject: Re: PARTING TROUBLE Here's a posting by the late teenut (Robert Bastow) on the subject from rec.crafts.metalworking. Best, Jude Miller >>> Most people treat the pre-ground HSS parting blades as a finished tool, ready for use. It is NOT! No more than a ground, square, HSS tool bit is a ready to use tool. Parting tools NEED side clearance. This must be ground into the blade before use. When re-sharpening has reduced the length of useable blade below the radius of the piece to be parted off..start again! Snap or grind off the short end and regrind side clearance on a new section. Fer Chrissakes..new blades are cheap enough to buy! Lets belay all this crap about whether the blade should be at, above or below center. ANY and EVERY lathe tool should be set at dead center height..PERIOD. If you get better results by not doing so..you are doing something WRONG and need to re-examine the geometry of your tool bit. Unless you are parting off SMALL diameters, and wish to reduce or eliminate the center "Pip", the nose of the tool should be ground SQUARE to the body. Any angle to the nose will, invariably, deflect the blade to one side, during deep cuts..resulting in binding, rough finish, non-flat surfaces or breakage. More importantly, an angled cutting edge produces a chip WIDER than the slot..how the hell do you expect this to escape freely from the cut? Better, even than a square grind, is a slight radius, or as I use a broad "Vee" shape to the nose..This flows the chip in on itself, producing chips that are noticeably narrower than the cut and which clear the slot easily. If you want to add belt to suspenders, use a tiny mounted point to grind a shallow, radiused groove LENGTHWISE in the top face of the tool. Examine a carbide, inserted parting tool tip, to get an idea of the best geometry to achieve. Chatter is reduced by INCREASING feed! Power feed will give best results. Rigidity of the entire set up is next to Godliness! Lock all slides not in use. Normal cutting speeds are the rule..Reduce ONLY if your rigidity is suspect. Reduce overhang to a minimum..both in the tool setup and the workpiece. Avoid Lantern type tool posts and Armstrong tool holders like the plague. Especially the angled parting tool holders..the worst abomination ever foisted on unsuspecting machinists. If you can't afford a rigid tool post..MAKE one! Rear mounted toolposts have definite advantages..Deflection of the tool or workpiece tends to lift the cutting edge OUT of the cut, rather than forcing it deeper...this by dint of the geometry involved. Mounting the parting tool upside down, in the front tool post, and running in revers, has the same effect. This same arrangement works wonders with broad form tools too. Part off as close to the chuck as possible. If a long overhang is unavoidable, or the parted off piece is relatively long..use GENTLE pressure from the tailstock to prevent whipping and chatter. Remove this just before final breakthrough or you may get a jam up. Judicious use of a fixed steady, a wedge of wood 'twixt toolpost and job, or, (dare I say it,) a well lubed hand, (NO GLOVES PLEASE!!) will also help to reduce chatter in these circumstances. Lubrication is a MUST except on free cutting brass and MAYBE good grades of grey iron. Drip feed or flood lubrication..matters not. Just bear in mind that a happy parting tool sounds like frying bacon. The instant it starts sounding grouchy..add more lube. Happy partings. teenut <<< ------- Date: Sun, 3 Jun 2001 13:57:41 -0500 (CDT) From: dswrx~xxwebtv.net Subject: Old, but worth repeating... Hi Lathe Lovers, Yesterday, I re-learned an old lesson; When "cutting off" ALWAYS put the tool point on the EXACT lathe center! Not above, not below, or eyeball it and get it "Close enough for government work" (what ever that means). I was machining brass to make washers for my crossfeed vise. I tried cutting off the little slices and stalled the spindle on my Craftsman 6". (no i was not using the backgears). The tool dug in, tried again, same thing. I gauged the point and found it was just above (0.10 ~ 0.20") the lathe center. I set the tool point to the exact center (point of 60 degree dead center in tailstock). Now, it cut the brass like butter (or margarine... if you are on a diet)! Nothing new, but little things are overlooked by ole guys like me. 8-) Leo (of course, i used cutting oil) ------- From: sleykin... Date: Tue Aug 14, 2001 8:28 pm Subject: Re: [atlas_craftsman] cut off tool problems/taper attach. wanted. A great tip from the recently departed Teenut ... Grind the parting tool with appropriate back rake and a square tip. Then with the corner of the wheel cut a shallow "V" in the center. This tends to cause the chips to turn in on themselves, giving more chip clearance and a cleaner cut. Other than that all the same old stuff applies .. lock everything down that dosn't have to move and feed rather aggresively. If you are using the lantern toolpost consider something more ridgid. I have an AXA style QC holder on my 12" and have no trouble (most of the time) parting off anything I can cut. Good Luck Glenn ------- From: James Meyer Date: Tue Aug 14, 2001 8:45 pm Subject: Re: [atlas_craftsman] cut off tool problems/taper attach. wanted. >Hi, I just joined the list. I am a maker of custom french horns and >therefore use my 12" Craftsman lathe to cut brass bar and tubing. Does >anyone have any suggestions on cut off tooling? I get a bit of chatter >etc. The shape of the business end of the cutting tool has a lot to do with how smoothly you can cut brass and copper and alloys like that. A cutting tool that works perfectly for iron and steel is exactly the *wrong* shape for brass. Brass cuts best for me if I use a tool with no relief under the cutting edge and very little "rake". The action is more like scraping rather than cutting. Jim ------- From: catboat15x~xxa... Date: Tue Aug 14, 2001 8:49 pm Subject: Re: [atlas_craftsman] cut off tool problems/taper attach. wanted. Cutting off is one of the more difficult lathe operations. First you may be feeding too slowly, tool is not ground correctly or not exactly on center. If you are feeding too slowly the tool tends to "skip" on the work producing chatter. Tool set too low or high will leave a "pip" on the stock. For many part off operations I cut a bit in one place, then back off and move over about 1/2 or 3/4 of the cut off tool width and cut another groove. This leaves plenty of chip clearance and makes cutting easier. A slight length-wise shallow groove in the top of the tool will also help keep the chip from jamming in the cut. If you are parting brass stock try using an oil stone for just a couple of swipes as if you were dulling the edge. Cutting on brass the tool tends to be pulled into the work, hogging and making a mess of your work and in worst case your tool. John Meacham High Desert of California, Palmdale, Littlerock. ------- Date: Sun, 07 Oct 2001 11:05:45 -0400 From: Richard Parker Subject: Re: cut off tool hates me > Why am I having sooo much trouble using a cut off tool? I follow the > directions. I'm taking my time. I'm eating right. I acknowledge a > higher entity. Is there a high/low cap or limit to what size stock > you can cut off? Parting or cut-off tools are traditionally a bit of a PITA, Hank. There's many variables to consider when they don't perform properly, and experimentation is usually the best way to learn "what works with what". Rigidity and on-center (or slightly below center) application of the tool is one factor. Naturally, you wouldn't want more tool hanging out of the holder than you need. Perpendicularity to the workpiece is a must, and thickness of the tool is yet another variable. Top rake geometry (or lack thereof) is yet another - some applications prefer a chip breaker, and some like no top rake at all. Increasing/decreasing side clearance and front rake can affect performance. Spindle speed can really affect things (some materials part better at high spindles, some prefer back gear). These are a few of the things that I can think of that affect the tool's performance, and any combination of the above might be right for one job but stinko for another (excepting rigidity, tool protrusion, and perpendicularity - those are constants.) Also, cutting oil should be constantly supplied via a small brush or squeeze bottle when cutting steel or aluminum - don't let the "race" that your cutting run dry. In most materials (other than free machining plastics and such), the cross slide should be fed by hand - and the feed rate is yet another variable. Take yer time, observe the action of the tool, and apply analytical corrective action using some of these points as a guideline. Try to part your work as close to the spindle as possible (again, rigidity). It may take you a little time, but you'll do fine eventually! Best regards, Rich ------- Date: Mon, 08 Oct 2001 02:55:01 +0000 From: Jon Elson Subject: Re: cut off tool hates me HUNLEY31x~xxaol.com wrote: >Why am I having sooo much trouble using a cut off tool? I follow the >directions. I'm taking my time. I'm eating right. I acknowledge a higher >entity. Is there a high/low cap or limit to what size stock you can cut >off? Cutoff is the hardest thing to do on light lathes, and is even tricky on the big ones. Some materials will not cut well. the tool height is critically important, speed is important too. You need to keep the advance going briskly into the work. Some materials work harden if you don't keep plunging, some develop chatter. Unlike some other tasks where reducing infeed helps with the chatter, on cutoff it often helps to increase the infeed rate. Correct grinding of the tip of the cutoff tool is also part of the trick. Some have recommended puting a Vee in the top of the cutoff tool, causing the chip to fold in on itself a bit. That gives the chip clearance in the groove. Lots of cutting oil is also part of the trick, this works wonders for me. Finally, if there is any looseness or free play in the stackup of carriage, cross slide, compound and toolholder, then you will have big problems. One little-known area is the gibs on the underside of the carriage. The high infeed force can lift the back of the carriage off the ways, if there is much clearance there. This will give you fits (and broken tools). Jon ------- Date: Mon, 08 Oct 2001 12:12:33 -0500 From: Jim Irwin Subject: Re: cut off tool hates me I've been making chips out of metal for about 45 years on the same Atlas 1042. Cutoff was a real challenge for me for most of those years. Several broken tools, dug-in & ruined bars and parts. I seem to have somehow "paid my dues" and now have no troubles. Maybe some confidence goes a long way. I use the Atlas cutoff tool holder with plain, straight across ground tip. The secret seems to be to set it right on center, not below, and use a sharp tool with minimal relief angle (made with the radius of my 6in. grinding wheel). Tool is extended only as far as the radius of the part being cut off + one RCH (red cat hair ...an old machinist's measurement ;>)) and the holder extended out from the tool post as little as possible and all tightened down gorilla tight (my term). That means all sources of play reduced to good'n'tight (German machinist's nomenclature ;>)) The key then is: align the tool exactly perpindicular to centerline, lock the saddle, use good lube, start & maintain the cut aggressively, evenly, firmly. Remember that as the cut progresses, you're cutting at ever-slower FPS, so adjust speed to be on the fast side at the start. If you get digging in, check the chuck jaws and dress if necessary to be sure they are tight in the chuck body and exactly parallel (when clamped down on the work) to the lathe centerline. My cutter is now ground such that I have had no trouble parting aluminum, brass, stainless, HRS and CRS. Best regards, Jim Irwin ------- Date: Tue, 9 Oct 2001 08:49:03 EDT From: AtlasTV48x~xxaol.com Subject: Re: cut off tool hates me I agree, The hack saw works everytime for me. I made a cute holder for my die grinder that fits in my QC tool holder. A 3 inch cut off wheel does a beautiful job on anything that I've attacked with only a 1/16 kerf. It also makes a nice tool post grinder for about $89 new. I always use a rubber mat with a tight hole what fits over the tool holder and covers the ways. Remember, always practice safe grinding. Dave ------- Date: Tue, 9 Oct 2001 13:04:05 -0700 From: "Bob May" Subject: Re: cut off tool hates me I find the discussion of cutting stock off fascinating! I've owned a Unimat for many years and have done all of my work with that machine unless there was a lathe available at work (I work in electronics) to do some larger stuff. I've had the problem you have all experienced with chattering and so forth much worse than what you've experienced. Remember that the Unimat has the carriage on a pair of rods that are suspended at the ends only and the carriage surrounds the rods? That makes the whole process of doing any work an excercise in keeping those rods from singing. My process in cutting off is to take a short cut with the cutter and then moving over a half a cutter and going a bit further on that side. Then back to the first position and do some more there. You only go about .050" at a time but you get the cut done and it's a nice smooth cut when you do a final pass getting the last thou on the face of the cutoff material before the final plunge. Bob May http://nav.to/bobmay NEW! http://bobmay.astronomy.net ------- From: Alan Marconett KM6VV Date: Tue Jan 15, 2002 4:25 pm Subject: Re: [sherline] Parting 2" dia. ABS plastic midroof wrote: > Hello: One of the projects I have on deck will involve parting off > some ABS plastic that's 2.0" in diameter. I'm wondering whether I'll > need to make a special cutoff tool holder and cutoff tool. From the > little I know about machining, I am thinking one should have a 0- > degree rake on the cutoff tool to prevent digging in the plastic. I > don't have my Sherline cutoff tool holder yet, but I believe it holds > the tool at a 7-degree rake. I would also think that I wouldn't be > able to get the cutoff tool at the center of the part with 1.0" of > tool sticking out of the holder. Do I need to make a special cutoff > tool and holder? Thanks. Bryan Hi Bryan, OK, I can be crude. Just cut a slight groove where you want to part it, take a hacksaw, and WITH YOUR HANDS OUTSIDE the HACKSAW FRAME, gently lower the hacksaw to the groove, and make light strokes back and forth as the spindle turns. It should be easy to cut ABS off this way. You should probably stop before the end, and finish with the spindle off. CAUTION: Please, anyone doing this, or filing, etc. BE CAREFUL! we want you to keep all your fingers! (required caution message complete). HTH Alan KM6VV ------- Date: Tue, 3 Sep 2002 20:57:51 -0700 From: "Dave Hylands" Subject: Interesting problem while parting I ran into an interesting problem while parting a piece of round brass stock. The piece was 3/4" in diameter and 4-5" long. I was using a steady rest and parting about 0.25" from the end. The steady rest was about 1.25" from the end (I had knurled about this much of the end). The very first part went very straight. The second and subsequent parts caused the brass stock to be pulled from the 3 jaw chuck (towards the tailstock). This, of course, casued the parting blade to bend and not cut straight. Retracting the parting tool, the starting slot was half of the width of the parting tool closer to the tailstock. I eventually wound up using the tailstock to prevent this from happening. Does anybody know why this would happen? Is there anything I can do about it? Or is using the tailstock the only option? If it can pull the work out of the chuck, presumably it can push it into the chuck? Any insight is appreciated. Dave Hylands Vancouver, BC, Canada http://www.davehylands.com/ ------- Date: Wed, 4 Sep 2002 07:49:34 -0500 From: "Nance, Tom" Subject: RE: Interesting problem while parting Hi Dave: You might want to check how your parting tool is ground. It should be fairly square when looking down from the top. If it has a point, it will drift to one side everytime. Tom ------- Date: Wed, 4 Sep 2002 07:54:18 -0700 From: "Marcus & Eva" Subject: Re: Interesting problem while parting Hi Dave: Here are the places I would look: 1) Make sure the parting blade is ground and set up so the cutting edge is exactly parallel to the axis of rotation. 2) Make sure the jaws of the steady are precisely in line with the cylinder you are supporting. Misalignment here will slowly crawl the part out of the chuck by working it against each successive jaw as it rotates. (To get a clear mental picture, imagine setting the steady deliberately way off and then rotating the bar in it. The chuck will start trying to act like a universal joint, and chew up the end of the bar until it can flop around.) 3) Sherline chucks won't grip with much force...their construction is pretty light, and the mechanical advantage of a Tommy bar vs a crown and pinion is low. Use the 4 jaw if you need better holding power. 4) Watch for wear of the jaws or the workpiece at the steadyrest location. Wear will act the same way as steady rest misalignment. Cheers Marcus ------- Date: Wed, 4 Sep 2002 08:01:41 -0700 From: "Marcus & Eva" Subject: Re: Interesting problem while parting Hi Tracy: Yes, this is what's commonly recommended in textbooks, but it doesn't work nearly as well on tiny machines. The rigidity of the blade is often a big problem. Sherlines don't have the poop to handle a wide, stiff blade, so often the blade will flex sideways with deeper cuts. If it snags in the side of the slot it either stalls the machine, spins the work in the chuck or snaps off the blade. These machines are actually pretty marginal for parting off...I hacksaw and face whenever I can to avoid parting on these tiny machines. Parted off faces usually look like a pig's breakfast anyway and need facing off to clean up. I'm too lazy to set up the parting tool and then flip the part for clean-up, and have to set up another tool. Cheers Marcus ------- Date: Wed, 4 Sep 2002 08:14:38 -0700 From: Wm. Dubin Subject: Re: Interesting problem while parting Dave, I have had this same problem, not just with cutting off, and not just with the Sherline, but with my 6" lathe as well. So far, the replies you've received all centered on the cut-off blade, but this is (in my estimation) not the problem, the problem is the steady rest, as this same problem happened to me while doing simple turning (using the steady). I checked with a friend in Australia, and he felt the problem is based on the steady acting as if it were a NUT, and the bar stock literally 'unscrews' from the chuck. My solution was to use the tail stock, only instead of a center (as my stock couldn't be end drilled), I put a 1/4" dia faced off steel rod in the tail stock chuck and brought it up to the work end, added grease, and went to work. I no longer use the steady rest without tail-stock support. Hope this helps. Wm. ------- Date: Wed, 4 Sep 2002 09:45:48 -0700 From: "Dave Hylands" Subject: RE: Interesting problem while parting Thanks to everyone for their input. I'll be keeping an eye on this in the future, and see if I can determine if it is in fact due to the steady rest. I first turned the brass bar (no tailstock and no steady). I was taking very light cuts (0.001 or less) because I was trying to measure the alignment of my headstock to the ways. I was able to get it within 0.0004" over 3-4" (probably not really that accurate since I doubt my skills at using the micrometer are that good yet). Once I got the headstock running well, I added the steady rest and snugged it up to the piece while it was really close to the headstock, then moved it out towards the tailstock. I used a small amount of oil on the stock where the steady rest touched it and then proceeded to knurl the end and part off pieces. The first one was really nice, and the finish was much better than I was expecting. I have some pictures, which I hope to post in a few days. The remaining ones weren't so nice. Fortunately, I added 0.010 to the cut, expecting to have to finish things off a bit nicer. The parting blade was new. I think I had used it once before to shorten the length of a threaded screw. Dave Hylands ------- Date: Wed, 4 Sep 2002 18:41:15 +0100 From: "David Simmons" Subject: Re: Interesting problem while parting I'll second that, small or big. I avoid parting tools as much as possible and just cut off the part with a hacksaw. That is after years in the trade when I worked on items far to large to even dream of using a parting tool. I prefer to make a jig for very thin parts - out of Al - that way I can face both sides. The jig is very simple - a disc with a rim around the edge and then split it about 2/3 across the Dia. That way you can still use the three jaw to hold it. Another little trick - don't try this at home kids - is to cut a vee groove a little wider then the hacksaw blade, then with the lathe spinning slowly press down evenly with the hacksaw from above - make sure the teeth are the right direction. Regards, Dave S. BTW: As a youth I was told that wearing an old tie around the shop was a great way to have an instant and handy rag. I don't think that guy liked me much:) ------- Date: Mon, 11 Nov 2002 00:40:33 -0600 From: Jon Elson Subject: Re: More about the lathe disaster kdspriggs wrote: >Here is the gruesome details about how I managed to break the >compound rest on my 10 inch Atlas. I was using a cutoff tool to cut a >3/4 inch bar. I had the lathe running at the lowest speed possible >(in back gear) and was keeping the cut well oiled. Unfortunatley I >had the compound rest extended almost all the way forward. I am sure >the tool was on the centerline as I took a lot of pains with that. I >was about 3/16 inch in to the bar when it caught and broke the the >compound rest right at the back side (or maybe you would call it the >front side anyway it was the side closest to the idiot running the >machine) of the tool post slot. WOW! Major mistake! Lucky you didn't get hurt! Anyway, the 10" Atlas compound is pretty weak to begin with, and gets noticably wobbly when entended far in either direction. The lathe manual says for heavy cuts that the compound be fully supported on the base. The wobbly condition of the compound makes it more likely that the tool will wobble and possibly dig in, too. You've got to have the stiffest support possible for cutoff tools. Jon ------- Date: Mon, 11 Nov 2002 23:27:32 EST From: AtlasTV48x~xxaol.com Subject: Lathe Disasters 
After several good scares and close calls with cut off tools, I have
reverted back to the trusty old hack saw. A cut off tool light enough
to break before the Atlas does takes more patience and time than the
hack saw but I do tend to get in a hurry.

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Date: Mon, 11 Nov 2002 07:17:12 -0800
From: Mark 
Subject: cutoff tools

My Dremel makes real nice toolbits from thin-kerf carbide tipped saw
blades. I roll my own for positive, zero, negative rake. A jeweler's saw
would do if you don't have a Dremel.

mark

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Date: Tue, 12 Nov 2002 05:15:16 -0800 (PST)
From: gauge-onex~xxwebtv.net
Subject: Re: Lathe Disaster

It sounds to me like the only error made here is the use of such a slow
speed - I do a large amount of parting off and have absolutely no
problems doing it... I would have parted off that piece of 3/4" steel at
about 500-600 RPM. Atlas lathes are not really rigid enough to part off
at back geared speeds.

I use a Carbide tool and a steady feed - too light causes chatter and
fine, splinter-like chips... too heavy a feed could probably break
something - I have only over-fed once... the tool dug in, stalled the
spindle and slipped the motor belt. (I was lucky I guess).

Anyway, you want to produce a fairly continuous chip. Mine usually come
out as little coils - like flat snail shells - and break themselves off
when they are about 1/4" diameter.

Make yourself a little gravity-drip oil can to take care of the cutting
oil so both hands are free to operate the feed. Lock the carriage to
the bed and tighten the compound gib screws. And of course, the tool
should be sharp, square, and perfectly on center.

Regards,
Jay Dee

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NOTE TO FILE: Also see the Sherline Lathe Quirks or Tips text file for
more parting hints in the discussion starting:
Date: Thu, 03 Apr 2003 05:13:44 -0000
From: "forbes_rl" 
Subject: Problem with steady rest slipping

A perfect illustration of how one topic completely changes focus in
the discussion to another (parting off).

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Date: Fri, 11 Apr 2003 15:07:32 -0700
From: Mark 
Subject: Question parting off Titanium

Silver soldered a broken 18 inch shank carbide pc-board drill into a hole
in a chunk of mild steel. Trimmed it down to about 40 thou thickness,
slight positive rake, squared tip for cutoff. Made a nice cut into the
side of a titanium rod, but I was amazed by the cutting tip - almost a
mm had come off the top surface, which is now rounded and somewhat
mottled. Looks like it had been ablated, not eroded by the Ti.

Is this a function of the carbide grain structure, or of my heating it to
essentially red heat for Silver soldering? Or? Any other suggestions for
grooving / cutoff of ti rod?

thanks/ mark

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Date: Fri, 11 Apr 2003 20:18:19 -0400
From: "Statman Designs, LLC" 
Subject: Re: Question parting off Titanium

All I do is titanium. Here is how I part it off, assuming a depth of cut
less than 0.250", maximum diameter for a solid bar of 0.5". I use a 1mm
full radius grooving insert. TiN coated helps if you are going to part off
50 pieces with one bit. The full radius prevents it from shattering when
it gets to the end. I also part off a lot of thick walled cylinders.

You can buy a mini grooving toolholder and insert from J&L for about $50
for the holder and $13 apiece for double sided inserts.

I can part a solid bar up to about 0.6" in diameter by snapping it off
manually after grooving to the full depth of the insert. Titanium is
fairly brittle (the 6/4 alloy) and snaps off easily enough. Then you do
a quick facing cut to clean it up.

Daniel J. Statman, Statman Designs
www.statmandesigns.com    dan.statmanx~xxrennlist.com

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Date: Fri, 11 Apr 2003 19:17:48 -0700
From: "Marcus & Eva" 
Subject: Re: Question parting off Titanium

HI Mark:
Carbide doesn't tolerate the stress of heating and cooling all that well.
I suspect that the corners just crumbled off the tool because of
microcracks in the carbide. I've had problems of the same sort with
brazed-on inserts ...especially homemade ones.

Clamping rather than brazing the carbide insert is the best way if you
need to preserve the physical properties of the carbide. In the case of a
round stub from a broken PCB drill, a simple setscrew is adequate.

Cheers
Marcus

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Date: Wed, 16 Apr 2003 07:13:50 -0000
From: "sikn1gh7" 
Subject: Re: parting off brass with a cut-off tool

Advice from my shop teacher at the Univ. of Washington --
Rules of thumb for parting:

* As slow as you can go. On our 14x40" lathes, we usually spin the part at
no faster than 200 rpm, even aluminum. We have the luxury of power feed
and we always use it, typically we feed at about 0.002" per turn but it
depends on the material. On the Sherline, I understand such slow speed can
be a problem. One thing I would love to see is a hack to put an extra
planetary gearbox (such as a power drill gearbox) into the headstock.

* Lots and lots of lube. Even for aluminum and brass which can be machined
   dry.

* Make sure your setup is *VERY* rigid. This means:
- Lock the carriage, if applicable (not on the Sherline).
- Never part more than part diameter away from chuck. Deflection will
   result in a loose setup.
- Never part diameter bigger than the height of the blade - you'll get
   deflection and chatter.
- Never, EVER part between centers.

Also: Check to make sure that the blade is running true. Remember, the
tool post can move, so before parting make sure the side of the blade is
parallel to your X axis.

That said - our most common technique for parting things off bar stock?
Horizontal bandsaw, then putting it back onto the 3 Jaw to face the other
end. Much, much faster - the bandsaw blade costs about as much as a
parting tool but it's less likely to break. :-)

Hope this helps!
Terence

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Date: Wed, 21 Jan 2004 14:07:42 -0000
From: "mmurray701" 
Subject: Advice on parting? [using a mill -- posted to taigtools group]

I've been trying to make a batch of round parts using my CNC mill as a
lathe. I made a toolpost and everything is working surprisingly well so
far. Facing and regular outside cuts are all working amazingly smooth.

But I cant seem to be able to part things off without chatter. I recently
bought one of those 1/16th wide parting tools on e-bay and this helped but
i'm still getting alot of vibration. I assumed it was because of my
homemade tool post, but all the vibration seems to be comming from the
headstock.

Any advice? Everything is tight. I've tried different speeds and feeds but
it doesn't seem to help. Is this all I should expect out of a Taig? How
well does the lathe part things off? I'm working with 1" aluminum by the
way. Thanks!

Mark

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Date: Wed, 21 Jan 2004 14:55:36 +0000
From: Steve Blackmore 
Subject: Re: Advice on parting?

Probably the toolpost rather than the headstock, it needs to be very
rigid. The more so the better. If you can try inverting the tool and
parting from the back (opposite side on the mill). Also keep the feed on,
it can be a bit of a juggling act, parting tools like a steady infeed and
probably at a higher rate than you would expect.

Steve Blackmore

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Date: Wed, 21 Jan 2004 15:27:55 -0000
From: "Ed Chesnut" 
Subject: Re: Advice on parting?

Cutting edge height on center?

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Date: Wed, 21 Jan 2004 16:25:08 +0000
From: Tony Jeffree 
Subject: Re: Advice on parting?

I suspect that this is a simple problem of stiffness - the mill's Z-axis
is almost certainly not as stiff as the lathe bed (consider - with the
lathe, you would be parting off near the headstock, therefore there is
only 3" or so of bed to flex; with your "mill that thinks it is a lathe"
setup, there is a considerable length of Z-axis to flex). Parting off
generally puts heavy loads on a lathe - I suspect you are probably just
working outside what the setup is capable of.

I have occasionally wondered whether the Z-axis column (which is basically
a piece of heavy gauge square section tube) would benefit from a concrete
filling to stiffen it, rather like the lathe bed; might improve matters.
Apart from that, if checking centre heights, using lubes (Kerosine/WD40)
etc. makes no difference, I would go for the old hacksaw-it-off-and-then-
finish-the-raggy-end-in-the-lathe technique (which I often use anyway if I
can't be bothered to fit the cutoff tool to the cross-slide).

Regards,
Tony

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Date: Wed, 21 Jan 2004 16:40:54 -0000
From: "mmurray701" 
Subject: Re: Advice on parting?

Thanks for the replies guys. The center height is good, Tried both water
based coolant and kerosene. I'm thinking I'm just outside my limits as
well.

The tool post probably doesn't help things. Its 1" square steel and about
2.5" high. But it really doesn't seem like the vibration is here. You can
put your hand on it and it seems solid, no vibration at all. On the other
hand, you lay your hand on the headstock and you can definitely feel it
vibrating. The column seems solid as well.

It still will part the thing off, just squeals really loud. Any reason why
I can't just let it chatter its way through? Is this going to damage
anything (other than my ears)?

I guess I could chop it off with the bandsaw after removal, but this would
slow things down considerably.

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Date: Wed, 21 Jan 2004 08:24:29 -1000 (HST)
From: Tom Benedict 
Subject: Re: Advice on parting?

I've been doing mill-as-lathe parts recently, too, and found an answer
for this.

Because of some constraints on the shape of the part, I've been using a
diamond point tool. It'd look like a threading tool except it's got a 15
degree included angle instead of a 60 degree included angle. The parts
I'm working on have features on the order of 0.002" wide, so there's
almost no tip radius on the tool.

When it came to parting I figured I'd plunge the tool into the work. At
that point the work is pretty thin, so no big deal, right? WRONG! I
destroyed a bunch of parts that way.

I was still looking for an answer when I had to make some parts using a
similar setup. Only this time the parts wound up being almost a quarter
inch in diameter at the point they needed parting. Plunging snapped a
couple of those tools (they're fragile as all get-out), so I looked for
another way.

If you don't mind a slightly wide parting slot, you can treat the parting
operation as a normal lathe turning operation. Plunge in a couple of
thou, take a light pass across your wide parting line. Go back, plunge in
a couple more thou, take a light cut. Eventually you whittle the thing
away to practically nothing and the part falls off. You're only ever
cutting with the very tip of the tool, so the cutting forces are minimal
at best.

On a manual lathe this would be tedious beyond tedious. In CNC it's just
more toolpath. No big deal. And the results aren't that bad. It parts off
the part just fine. The only drawback is you eat more material doing it
this way.

Tom

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Date: Wed, 21 Jan 2004 21:48:02 -0000
From: "mmurray701" 
Subject: Re: Advice on parting?

Tom, thanks for the tip. The point of my new parting tool is basically
square so I'll have to re-grind it but that isn't much of a problem.
I'm sure this will work.

I actually used to use this method when trying to part things on my
father's Unimat (a nightmare!), just didn't think about doing it here.

Thanks!
Mark

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Date: Fri, 23 Jan 2004 20:48:46 +0000
From: Clive Foster 
Subject: Parting off and back Tool Posts

Folks: Back tool posts are an effective and widely used panacea for
chatter and other parting off problems on small lathes but the magic is
more in the action of the feed screw than in the position of the tool.

With a conventional front tool post the screw is pushing the tool into
the work. Being a slender column it is obviously weak in bending and,
given half a chance, will try to run away from the load by buckling.
Obviously it can't collapse completely but it will bow and any change
in the pressure on the tool point will alter the amount of bow needed
to support the load so, unless we can keep an absolutely constant
pressure the screw will effectively be trying to" vibrate" in a transverse
mode. Such vibration will change the feed slightly which in turn will
change the load re-enforcing the effect (us techies call this positive
feed back) so it doesn't take long before you have a nice chatter going.

If you have a back tool post the cutting forces are put on by pulling
the feed screw so it is in tension. Even the thinnest piece of steel
wire takes a fair load to stretch it (tried tuning a piano recently?)
so basically even the smallest of screws wont allow the feed to change
with load variations effectively breaking the positive feedback. As
long as you have enough feed load to keep the feed nut and screw in
positive contact the tool will advance nicely through the work.

I think it would be well worth seeing if the feed screw can be
re-arranged to be held at the back, working in tension. This ought to
improve cutting capability and finish with normal tools as well as
helping the part-off process. A normal fixed bearing at the back
(angular contact ball race??) with a "Alinbal" type bearing (like a
ball rod end) at the dial end seems a good way to go.

In my view the major advantage of the back tool post is that its pretty
much a permanent fixture making it worth taking plenty of time to get
the tool alignment absolutely right so it cuts straight across without
arguing with the side of the cut.

George H Thomas describes some experiments with different parting tool
tip shapes in his book "The Model Engineers Workshop Manual". The shapes
look fiddly to produce but I can vouch his the demos were convincing.

HTH.
Clive

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Date: Thu, 15 Apr 2004 18:55:02 -0700
From: Don Rogers 
Subject: Re: cutoff tools

I'd like to make a couple remarks about the cutoff tools.  Setup on these
are very critical.  There is no relief along the tool. That means that the
tool has to be exactly perpendicular to the work axis. I use a 1" sq tool
bit as a square setting up cutoff blade. No amount of lubrication or tip
grinding will prevent this need.

Now, for the tip of the tool. When grinding the tool, don't grind the top
of the tool. Any grinding there will cause a wedged shape tool, with the
cutting edge at the narrow point and a scrapping edge along the sides. The
face of the tool needs to be cut at an exact 90 degrees to the top of the
tool. 89 Degrees will cause the tool to try to wander when pushed into the
work.

The cutting edge of the tool needs to be set exactly on the axis of the
work. Too high, and you run into a area of the tool where it won't cut the
last bit and jams. If it is low, then you leave a small rod in the center
and the closer to the center the cut gets, the more the cutting angles go
to hell.

Keep the blade as close to the support as possible.  Two inches of tool
projecting past the holder is not needed for a 1/2" cut. It lends to a
bent or broken blade, or one that overheats and looses hardness.

Last, parting is not a process that you can ease into, it takes brute
force. The variable speed spindle is nice in that you can increase speed
as you get nearer to the center to keep up the ft/min cutting speed to the
best results. Just remember that 1/4" rod that is sticking through the
head stock by a couple feet and was wobbling around a bit will wobble a
lot and may bend as the speed increases. If you are feeding a long rod
into the lathe, support is necessary, and not just under the rod, but
enclosing it.

Don

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Date: Thu, 18 Nov 2004 09:05:54 -0800
From: Don Rogers 
Subject: Re: parting off [taigtools group]

>Does anyone have suggestions as to a better setup or the best way to
>grind and sharpen the cutting tool?

On Sharpening the tool, only sharpen the end of the tool, never touch the
top or sides. Keep the cutting tip exactly square with the length of the
tool.

Absolute alignment is required for success with a parting tool. I keep a
1/2" tool bit at had to use as a mini square when aligning the tool to the
work. If you are off by just a tenth of a degree, the tool will drag on
one side, bending the tool and it just goes down hill from there. The the
tool wants to be exactly on center. Too low and you lose your cutting
angle; too high and you don't have relief and the body of the tool hits
the work.

The quick change post on the Taig has it's problem in that there is a lot
of leverage from the tool to the center post, and it is quite easy to turn
the post when applying tool pressure like needed for parting, or even just
tightening the QC clamp. The 10-32 screw just doesn't have enough pull to
lock the post and it's riser to the cross slide. I think that doing a
relief cut on both sides of the raiser would help this.  Make sure the
screw will fully tighten without bottoming in the T slot, but be fully
engaged in the nut. This takes some washer work on the top to get it just
right. You need all the holding power you can get.

One other idea comes to mind as I am writing this. A top plate for the
cross slide, from 3/8" cold rolled steel, four corner mounting, maybe an
additional two in the center, drill pattern of 5/6" NF holes and then
replace the center screw with a 5/16 stud and nut on top. You will have to
bore out the top of the blue center post to accommodate the 5/16 stud, but
there is plenty of relief on the bottom part of the center. A slight
relief on the bottom of the black body would be in order using this
approach. Really tightening down on the stud may distort the bottom of the
black body enough to loose it's grip on the plate. You would also want to
countersink the threaded holes in the CRS so you don't have a thread pull
up and cause you to lose the fit.

Don

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Date: Thu, 18 Nov 2004 11:10:10 -0600
From: "Bad Brad" 
Subject: RE: parting off

>I've been having trouble lately when using the parting tool.  I'm
>using the TS Engineering setup with a 1/2 blade.  The problem is that
>I am getting loud screeching sounds and chattering.

Make sure your tool hieght is correct, sounds like your tool is to high.
Run the slowest spindle speed you can and use a ton of lubricant. Also
there should be proper clearance. Don't stone the top edge of the cutting
point by hand because you will round the corners and the bit will wedge
into the cut as a result.

I sharpen my cutoff tools at a 30 deg. angle from flat just on the
outboard end only. Make sure the cutting edge is square to the edge of
the tool too.

Happy cutting!
Bad Brad        Rabid Weasel Racing Team

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Date: Mon, 23 May 2005 01:23:43 -0000
From: "David" 
Subject: Parting Chatter [taigtools]

I just could not part anything without severe chatter, so guess what
solved it ? A hand crank on the chuck spindle. Just turn it about 2
rpm. Better than sawing it and re-chucking and facing.

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Cheap parting /cut off tools [atlas_craftsman]
Posted by: "Ted Lotz" mototedx~xxyahoo.com
Date: Sat Nov 18, 2006 4:53 pm ((PST))

Hi there, I've had my "new" lathe for about 6 months now (1941 12"x 36"
from the original owner, he was 82 years old and bless his heart he was
crying when I loaded it up and left his driveway). Thanks for all the
useful inforamtion in this group. Haven't seen this tip before so I
thought I'd run it across you guys. Was playing around last night in the
shop and took a 7 1/2" carbide tipped circular saw blade that had a few
teeth missing to the old bandsaw, cut it into 1/2" wide strips to fit my
parting tool holder and presto, free parting tools that cut fantastic.
They seem to have a small angle on the carbide tip, but hey, one trashed
40 tooth blade will make at least 20 parting tools.

Ted,
Proud owner of a classic American made lathe.

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Re: Cheap parting /cut off tools
Posted by: "Ted Lotz" mototedx~xxyahoo.com
Date: Sun Nov 19, 2006 4:53 am ((PST))

> Hi Ted, I can sympathize with the former owner! It's kind of like
> closing the book on one's life when it comes time to dispose of your
> tools & toys! So far as the cut off is concerned; what a great idea.
> Now, how did you cut the blade into strips? I assume, you used your
> bandsaw. How did the blade fare? Cheers, Jay Greer

Seems that circular saw blades are made of a softer metal than it would
appear. I've just got the common 4"x6" bandsaw and it sliced up nicely,
just be sure and miss the carbide tip!

Good luck,
Ted Lotz

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Cut-off tool for 6" Atlas [atlas_craftsman]
Posted by: "allan.ostling" aostlingx~xxgmail.com
Date: Tue Oct 9, 2007 9:49 am ((PDT))

I've recently acquired a 6" Mk.2. The carriage is now de-shimmed, the
bed is leveled, and I'm ready to make some first chips. But I'm
stymied by the first thing I plan to do.

I have a 12" length of 4" dia solid Delrin. I want to cut off 0.5"
lengths, discs on which I will do subsequent turning and facing. I was
thinking of using a cut-off tool, making a groove perhaps an inch deep
on which I could then use a hand saw to complete the through cut.

I can just manage to grasp the end of the 4" diameter in my 3-jaw,
with the jaws reversed. The other end is supported on a live center.

I can't use a cut-off tool in a holder mounted in the tool post -- the
cross-slide travel is not great enough to initiate a cut at a 4"
diameter. I'm wondering if I can achieve my needed cut-off capacity by
using the Cut-Off Tool Block, accessory #10106. This is substituted
for the conventional tool post, and provides greater rigidity. I don't
have this, so I can't try it to see.

--------

Re: Cut-off tool for 6" Atlas
Posted by: "LouD31M066x~xxaol.com"
Date: Tue Oct 9, 2007 10:00 am ((PDT))

Since you are not going for extreme accuracy a temporary tool fabricated
from whatever comes to hand will probably get you from where you are to
where you want to be. Don't be afraid to think outside the box and it
does not have to look elegant or last longer than the last cut....although
better to build better than you need to in case you might want to make
more. I have a little experience with turning Corian that worked out just
fine. Delrin may be subject to digging in. I  would advise to get a piece
to practice on to get used to how it goes.

Louis

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Re: Cut-off tool for 6" Atlas
Posted by: "Paul DeLisle" ferretpdx~xxgmail.com
Date: Tue Oct 9, 2007 8:13 pm ((PDT))

As some else said, think outside the box.

Using the whole piece, cut/face the front (most complex) side of the piece
you want. Then take a fine Sharpie marker (or a pen/pencil), and mark
about 0.6" back from the edge, at several places around the piece.

Spin it up on the lathe, and connect the dots with the pen. Then, take
a hacksaw, and *carefully* start your cut.once you have a clean groove,
start sawing away.

If you're lucky-enough for the piece you want to be flat-backed, sand it
smooth on a Surface Plate, or a tabletop with sandpaper. Otherwise, chuck
the remainder up, and start cutting carefully.

Repeat until you have enough pieces, or until you're out of material!
Hope this helps!

Paul DeLisle

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Re: Cut-off tool for 6" Atlas
Posted by: "jmartin957x~xxaol.com"
Date: Wed Oct 10, 2007 7:58 am ((PDT))

You've got a couple of problems, because the lathe really isn't big enough
to do what you want. But people with small lathes often find ways to stuff
work in them that the lathe wasn't designed to handle. So, there may be
ways to do what you want.

The lathe will not swing a 4" piece over the cross slide. Close, but not
quite.

But - you can remove the cast piece which covers the cross slide ways, and
you'll have your 4". The cast piece also holds the cross slide feedscrew
nut, so you'll have to put some washers or something in its place.

Or - you can work off to the left of the cross slide. There are a number
of ways to do that.

A right offset cutoff toolholder, held in your lantern toolpost, may allow
you enough clearance to get the 1/2" thick pieces.

A straight cutoff toolholder might work if you turn the compound slide
parallel to the lathe axis (or even aimed back toward you a bit) and feed
it out to the left of the carriage. Be careful, though, as the compound
slide can break.

A boring bar would probably give you the clearance and feed you need.
You'd have to grind up a cutoff bit for it.

For Delrin, you could always try a handheld cutoff tool, such as a wood
turner's parting tool. For a tool rest, try a boring bar.

Lots of ways to skin a cat.

The tool block would probably work, although you might have to remove the
way cover as above.

Supporting the piece with the tailstock is a must in this case. You'll be
finishing the cuts by hand anyway.

John Martin

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Re: Cut-off tool for 6" Atlas
Posted by: "allan.ostling" aostlingx~xxgmail.com
Date: Wed Oct 10, 2007 5:05 pm ((PDT))

John, I can tell you have swung a 4" diameter. You are right, removing
the carriage guard cover is all that is needed to make this possible.

I took your advice, turned the compound parallel to the bed, and saw
immediately that this does the trick. I can use a cut-off tool without
interference. This was a forehead slapper, when I saw what I'd overlooked.

Allan

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NOTE TO FILE: Cutting off yellow brass is a thread in atlas_craftsman
starting Apr 5, 2008 and that conversation may be found here on my
site in the file called Turning Brass. [Yes that thread could have been
put into this file but the conversation includes some general turning
information applicable to turning brass, as well as comments on rigidity
of the lathe involved.]

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