This text file is dedicated to various methods of indicating, centering, locating, and/or measuring a workpiece or tool position. 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. 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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. ========================================================================== From: Date: Sun Dec 5, 1999 4:03pm Subject: Re: Shop Tip In a message dated 12/5/99, eidolonx~xxe... writes: << Does everyone know how to use a DTI for mill centering between two opposite edges without having to know/calculate out backlash? >> If for example you have a piece with two parallel sides you can place an angle plate on one side against the work piece. Then you can indicate the other side of the workpiece, then the side of the angleplate for the other side, using both measurements approaching from the same direction, I hope this what you meant with your question. bill ------- From: Date: Sun Dec 5, 1999 4:03pm Subject: Re: Shop Tip In a message dated 12/5/99, cmsteamx~xxa... writes: << Does everyone know and use the Bedside Reader Tip on using cigarette paper for work location? >> I use it all the time on the mill for all axis. Long before the bedside reader came out. Most of the hints are in earlier Popular Mechanics Shopnotes from the 50's and earlier. Anyone got any of them for sale? Contact off list. In using the lathe, I use a tool to get very close with the four jaw, then if needed I get the DTI out and go from there, the tool bit is usually very fast, and you can make direct measurements from the cross slide, and this way you don't overtravel the DTI, which can be a real danger to it. ------- From: Date: Sun Dec 5, 1999 4:30pm Subject: Re: Shop Tip In a message dated 12/5/99, WAnlikerx~xxa... writes: <> I should have added the line, take the reading derived from those two locations, divide by two, and add to the indicated location, to get the center line, again approaching from the same direction. bill ------- From: Steve Clark Date: Mon Dec 6, 1999 10:01am Subject: Re: Shop Tip [Note: think he may have been alluding to a much earlier post as to wrong method here.] Unfortunately, this method will leave you off center by 0.5 times the dial test indicator ball. The method I use is to zero my hand wheel by turning past 0 by about 5 thousands on the test indidator, then set the zero as I crank away form the workpiece center. After this, I move to the other side and record the reading as I crank toward the workpiece center. This way both zeros are found while cranking in the same direction - thus eliminating backlash. The total reading you will get is actually the workpiece width plus the test indicator ball diameter, but when dividing by two the ball diameter cancels out giving the true center location. If you do this in this order (away from center then toward center), you can go directly to the center point rather than having to crank past and back up. ------- From: Gregory Gagarin Date: Mon Dec 6, 1999 11:08pm Subject: Re: Shop Tip -- Revisited When I mentioned these two (5&6) subjects I assumed (as is often the case) that something I only discovered, or figured out, recently had been known by everyone else since the beginning of time. I think that's true about 5. (Rich Dean has a refinement of the idea) but I'm not so sure about 6. so I'll send up a trial balloon for the pros to shoot at. About 2 months ago I had a large semi-finished cylindrical piece of stock mounted horizontally (attached to an angle plate) on my mill oriented lengthwise along the X axis. I needed to center the spindle VERY accurately (in the Y axis) over the stock to mill it along its X axis on center. My edgefinder shoulder would not clear the cylindrical edge and I wanted to avoid using backlash numbers in the calculations -- I've never trusted them to be consistent in different locations of the lead screws. After a lot of head scratching, I came up with a technique that worked so well that I use it routinely now when I have to be very precise in centering or want to avoid marking work surfaces(as with edge finder): 1. Set the Y handwheel such that it reads "0" when the ruled scale (on the Y axis bed) is on one of the graduated lines. Now you can read out a complete relative Y axis position and don't have to count handwheel revolutions. 2. Mount a DTI in the spindle offset such that it sweeps a small (about 1") circle at the tip and with the tip pointing near vertical (for sensitivity)slightly outside the circle. 3. Move up to the stock, sweeping the spindle (and DTI) until the DTI just touches the stock on its sweep and adjust the Z axis to the required test point (max deflection to center on a cylinder). 4. Use clockwise rotation to move the spindle closer until the DTI reads some convienient number (say 10) as a max value when swept by the stock. Your stock is now 10 thousandths inside the circle around the center of the spindle. Record the Y position (scale + handwheel) as you would on a dial caliper. This is your front relative position. 5. Move the spindle/DTI to the other side of the stock without disturbing the DTI setup. You can go around or over, or both, but you then must return the X and Z to the same settings you started with (in front) after you get it to the other side. 6. Back the spindle/DTI (counterclockwise Y handwheel turns)until the sweep shows the same maximum number on the DTI. Now take out the backlash by continuing moving the spindle in to say "25" (more than the expected backlash beyond the desired "10") then reverse and go back to the "10". You have now taken out the backlash and returned to the same offset on the backside as you had on the front. Record this rear relative position (scale + handwheel as before). 7. Subtract the smaller position from the larger position -- divide by 2 -- add this to the smaller position (or subtract from the larger). This is the desired center position -- scale + handwheel. Note: you never determined or needed the stock width. 8. Remove the DTI and move the Y axis to the above position using the scale and handwheel values and finishing with clockwise rotation. DONE. This takes a lot longer to describe than to do. Just don't forget that the key is in sweeping the edges (not static measurements) as we are looking for measurements along the intersecting edge and circumference of the DTI arc and not to disturb the DTI in the spindle or it's point setting. With slight modification this procedure can be used on non-parallel edges to find the center between two points on the edges. That's another story. I have only gone to this length in description since DTIs and such arrive without instructions and, for me, work locating has been a chalenging experience of discovery. Hope someone finds this helpful. Greg ------- Date: Thu, 18 Jan 2001 15:25:21 EST From: wanlikerx~xxaol.com Subject: Re: Centering a Rotary Table Make a plug that will fit the rotary table center hole very accurately, with a center cross scribed on it. Put the plug in the rotary table, then use a center finder in the spindle to find that center and fasten it down. There are several types of commercial and home built center- finders available, but in an emergency put a blob of clay on the end of the spindle, and insert a pin, center the sharp end by turning slowly and use a piece of metal to get the end of it to spin accurately on center, with no wobble. Carefully line the two up, and you can end up very accurate. Use a magnifying glass, but don't dislodge the pin, could hurt you. This is known in the ME magazine as a sticky pin, centerfinder, and it works well, if used carefully, don't spin too fast. bill ------- Date: Thu, 18 Jan 2001 19:38:17 EST From: sgut1x~xxaol.com Subject: Re: Centering a Rotary Table Gavin, I put a dial indicator in the spindle and roughly center the rotary table under it so that the indicator tip just touches the inside of the hole in the center of the rotary table. After that you simply move the x or y axis a bit then rotate the indicator along the inside of the hole. If the needle moves, you adjust along the axis using the handwheels. Once you've dialed in one axis you dial in the other. This might sound confusing but it is really quite intuitive once you try it. I think centering the rotary table is rather fun because you can move it so precisely using the x and y axis feeds. You can effortlessly move that .0005 needle until it is perfectly still. It sure beats tapping ever so gently with a hammer on one side of say a vise then tapping ever so slightly on the other side to line it up. Hope this helps, Stephen G. ------- Date: Thu, 18 Jan 2001 21:04:23 -0500 From: ron ginger Subject: Re: Centering a Rotary Table Gavin Eyre wrote: > Can anyone give me some suggestions on the best way to center a > rotary table so that the axis is aligned with the Z-Axis of the > mill? I am making a number of small connecting rods for an O gauge > loco and need to be able to mill small circular areas at the ends of > the various rods and links. Depends on how exact you need it. If all you are doing is the outside of a rod end, then I would turn a simple cylinder with one end the dia of the tables center hole, the other end 3/8" , or whatever end mill you plan to use. Id stick this into the mill collet, the other end into the rotary table, then I tighten the clamps and lock the table down. I suspect this will put it within 2-3 thou. If it needs to be 'spot on' to within a thou or less, then use an edge finder, and the 'Osbourne manouver" I think its called. First you need to accurately know the diameter of your table, then you set the mill to an 'eye-ball' of the center. Next you go to one edge of the table, say X first, pickup the edge, set your DRO to zero (you do have a DRO of course:-) then go to the opposite edge, find it. Take the distance moved, divide by 2, and move X back to that location. Repeat the steps, this time on the Y axis. Repeat again in both X and Y, and you are about as close as you will ever get. This requires an edge finder, which is a fairly cheap tool and very worthwile for a mill. ron ginger See Guy Lautards Second Bedside Reader for an explanation of this, including some math to prove its as close as you can measure in only 2 or 3 moves. ------- Date: Fri, 19 Jan 2001 16:19:54 -0000 From: khgrantx~xxix.netcom.com Subject: Rotary Table tolerances? The discussion about centering the rotary table reminds me that the last time I tried to center mine, I noticed that the center hole was not exactly concentric with the rotation. Indicating on the inside edge of the hole and rotating the table resulted in an eccentricity of about 0.0005 or more (it was several months or more ago; I don't remember the exact figure). What do others see with thier Sherline rotaries? The other thing I noted at the time was that the surface of the table wobbled a bit as it rotated. That is, with indicator in spindle, indicate off the top surface of the rotary table near the outer diameter. Rotate table and note deflection. I don't remember the value, but I was disappointed in the amount of runout. What do others see for this value? Keith ------- Date: Wed, 14 Feb 2001 16:11:54 -0800 From: Alan Marconett KM6VV Subject: Re: Wiggler. Hi Rogerio, As I understand it, the sharp tip of the wiggler is first set true by running the spindle relatively slow, and "pushing" on the tip with a piece of metal. Once running true, you can shut off the spindle motor, and bring the tip down near a cross hair scribe on a part. Use an 8x loupe (unless your eyes are better then mine), and move in X & Y until centered underneath the sharp tip (but don't disturb the tip!). There are other "tips" in the wiggler bag, the "small cyl" one can be "trued" as above, and kept spinning, brought up next to an edge, and when it just touches, it will "flail" out of true. Wigglers don't themselves "find" the center of a part; you can find the edges, and "dial" over to the center (do X, then Y), given the dimensions of the part. Hope this gets you cutting! Alan KM6VV P.S. Any more uses? I'd like to hear about them also! ------- Date: Wed, 14 Feb 2001 22:27:01 -0500 From: "Marshall Pharoah" Subject: Re: Wiggler. I've been using one for a few months now. I true up the needle point with my thumbnail. Therwise, just like Alan said. The round ball tip is a good edge finder, as is the .100 cylinder. These I find work best to let them wobble quite a bit. As you move the work closer to the wiggler you'll hear it start ticking. Eventually the ticking stops as it rubs constantly. Slightly closer and the ball (or cylinder) will jump to the side. I think this is actually the same motion an edgefinder works on. The bent shank unit is actually an indicator holder I've been told, but haven't really used it yet. To use it to find the center of a solid bar held vertically in the vise, you would be looking for one side and front or back. There is a hunt algorithm that works for this, but I don't have the book handy. I usually just use a lathe to find the center. Marshall ------- Date: Wed, 14 Feb 2001 22:05:56 -0600 From: "Al Lenz" Subject: RE: finding the center of a hole ( was Wiggler). Marshall and list, Just how is the best way to find the center of a drilled hole? The other day I lost my coordinates and had to re-zero on a 10-32 tapped hole. I know that I have read a dozen posts on the best way to do this, but suddently went brain dead. I put a dead center in the spindle and lowered it down til it "looked good". That didn't seem very scientific. Then, took a 10-32 cap-screw and turned the head true. Screwed it into the hole and then used and an edge finder to locate. This was OK for the purpose, but that isn't what I'm trying to remember, (or is it?) Al PS. The part was a 3 X 3 X 3/4 piece of scrap 6061-T6 that turned into a $375 part for my son's 928 Porsche. It fit "like it was made for it". The first "REAL" part made with my new CNC setup. And these are toys? ------ Date: Wed, 14 Feb 2001 20:36:05 -0800 From: Alan Marconett KM6VV Subject: Re: finding the center of a hole ( was Wiggler). Al, What's the Porche part? I've used a "dead center" before, I'm told you can still be off a few thousands. The cap-screw with "trued" head sounds like using what I think they call a "button". Should work great! You can indicate three points on the inside of a "clean" hole, and calculate the center, but with threads?? I don't think so. Alan KM6VV ------- Date: Wed, 14 Feb 2001 21:35:14 -0800 From: "YK Chan" Subject: Re: finding the center of a hole ( was Wiggler). Here is my two cents. Preparation: Bearing ball: 1X < dia. < 2X. Steel plate or USA razor blade. Dead center. Action: Chuck or collect a dead center to the mill/drill. Place the ball on the hole. Move the dead center tip above the ball. Place the blade on top of ball. Drop the mill to GENTLY hold the blade. Any off center will show up on the blade plane. Adjust until blade is horizontal to the mill table. End of Action. YK Chan in Seattle area. ------- Date: Thu, 15 Feb 2001 00:33:52 -0600 From: "Al Lenz" Subject: RE: finding the center of a hole ( was Wiggler). To YK, thanks, that is excellent. Your idea would have been quicker and better. The hole was drilled, tapped and chamfered, just perfect for your application. Your tip will be useful "next time". To Alan, the 928 has a rather unique coupler in the steering shaft that only comes as an assembly, thus the high cost. My son did it up in Autocad and we watched in awe as it was cut. Sort of a rounded corner square piece with raised oblong lands and oblong holes. Four 8 mm slotted holes cut with a 1/4 end mill, (couldn't do that without CNC). HAVE done similar with a file tho no comparison to the accurate final result. al ------- Date: Thu, 15 Feb 2001 12:18:41 -0000 From: ballendox~xxyahoo.com Subject: Re: finding the center of a hole ( was Wiggler). Al, lotta answers to your simple question. small hole, big hole, threaded, not threaded. Accuracy needed. All these need to be part of the answer. Having said that, there are precision equivalents of your "turned capscrew" that are used as you used yours. A "shoulder screw works well if you have one in the right thread size. Also many machinists carry sets of threaded "transfer points", which can be used with a wiggler or "center finder end" of an edge finder. The cone of the center finder will work with (is designed for) small holes. Threads will mess it up, tho; so it only is good for drilled/reamed/bored holes. Larger holes can be edge-findered in three points, with geometry filling in the gap... (remember that a right angle whose vertex is on the circle, will have 'legs' which intersect the circle on the diameter.) Halfway between the two points which make the diameter is the center. Hope this helps. Ballendo ------- Date: Thu, 15 Feb 2001 12:32:30 -0000 From: ballendox~xxyahoo.com Subject: Re: finding the center of a hole ( was Wiggler). YK, this is an excellent method as long as the hole edge (AND your dead center) is "sharp". And the material is FLAT. You can use any "true" point in the spindle... A similar technique is used to set tool height on the lathe. Chuck the material, blade is vertical between tool and work; when blade is vertical, tool POINT is AT center of stock. Also to get the tailstock back to center after an offset. With the sherline, you can put the point in the spindle and tailstock, with the blade in between, BUT... this will only align the headstock to the tailstock! Fine for between centers work. If the tailstock is not accurate, turning with a chuck could create tapers using this method of alignment. Use a test bar, and/or indicator... Thin steel shim stock can replace the razor. Hope this helps. Ballendo ------- Date: Thu, 15 Feb 2001 13:00:00 -0000 From: ballendox~xxyahoo.com Subject: Re: finding the center of a hole ( was Wiggler). > The cap-screw with "trued" head sounds like using what I > think they call a "button". Alan A tool makers "button" is a different thing. It is used to 'set up' a hole location more accurately than scribing, not to "find" an already machined hole. It is essentially a ground round bushing, with a screw through the middle, with "play" between the two. In use, the work is marked out and scribed as usual. Holes are drilled and tapped in the location(s) where button(s) will be used for ACCURATE location. The buttons are screwed into place, and snugged down... next the buttons are "adjusted" into accurate position (according to the part drawing) using whatever means of measurement makes sense. For example, say you have two holes which need to be EXACTLY one inch apart. You have placed two 1/2" diameter buttons in rough position. First you get one button adjusted until it is centered on the desired 1st hole position. Then, you 'mike' ACROSS the buttons "adjusting" until you have a reading of 1.500 inches. The buttons can now be used to 'dial in' the position AT the hole-making machine. AFTER the hole location is dialed in, the button is removed and the REAL hole is machined. This is a simplified explanation; most older machinist texts will detail the procedure. We don't see these as often now because our "commercial" cnc tools are so accurate, that we just program 'em, check 'em, and trust 'em... But it's a useful thing to have in your bag of tricks... Hope this helps. Ballendo ------- Date: Thu, 15 Feb 2001 08:23:51 -0500 From: "Marshall Pharoah" Subject: RE: finding the center of a hole ( was Wiggler). A Blake Co-ax indicator would probably be the best method. Second best would be a chinese clone of same (requires rework before use). For us ordinary mortals, a regular DTI mounted on an arbor in the spindle will work. You just spin it, adjusting the table as required until you get a zero reading, or as close as you feel works. You will either need a small mirror to read the indicator, or suffer a twisted neck. (don't spin it under power!). Another method I use which might be frowned upon, but has worked well for me is a low tech approach. I have a series of precision ground drill rod which fits the collets on my mill/lathe. This is ordinary O-1, but W-1 or A-1 would work, it's the precision ground that makes it work. This should be in the collet or mill holder and be tight enough that it sticks, but loose enough that you can grab it and slide it by hand. Anyway, If the hole I need to indicate in is the same size as one of these, then its just a matter of zdjusting the table until it drops in without binding. Otherwise I turn a tight bushing. This probably get you within a couple of thou, depending on the tolerances of your bushing, etc. You can also use a solid shaft which fits tightly in the hole, or toolmakers buttons if you have them and the hole is the right size, and then use an edge finder. The DTI is the preferred method. Marshall ------- Date: Thu, 15 Feb 2001 08:30:20 -0500 From: "Marshall Pharoah" Subject: Re: finding the center of a hole ( was Wiggler). I covered the first part of you question, but forgot about the tapped hole. By the very nature of tapping the hole, you've lost the exact center. Taps will cut a few tenth too one side or the other at least. What you did was probably close enough. There are precision tools made to do the same thing, but not worth the bucks unless you do it a lot, or need more accuracy. Marshall ------- Date: Fri, 16 Feb 2001 19:18:05 -0800 From: "YK Chan" Subject: Re: finding the center of a hole ( was Wiggler). Thanks to the update, tapped hole is not good for the ball anyway. As far as the subject it addressed the problem. In case of tapped hole, "ball ended" a correct size threaded rod to represent the ball. Hint, place a "true" nut to take out the slag between the hole and the rod should optimize the result. Hope that helps. YK ------- Date: Tue, 20 Feb 2001 15:17:06 -0800 From: Dave Martindale Subject: Re: Re: Problems Fly Cutting At 15:50 20/02/01 -0500, you wrote: >oI recognized the problem as being >an out-of-alignment situation with my milling head, so I pulled out a >piece of 1/4" optical flat glass (heavy, and supposedly true) and >pluncked it on my milling table. Using a dial test indicator, I got the >head trued up left to right, but then I found the readings front and >back were lower than along the length of the table. > It finally dawned on me that the weight of the glass was deflecting >it as it hung out over the front and back edges of the table. I then >shimmed things so the deflection was even on both the front and back >when the plate was equally positioned. Things have worked well since. You might want to check the flatness of the glass even when it's not overhanging the edge of a table. True "optical flats" are flat to a few wavelengths of light or less - better than a good surface plate. But to be stiff enough to hold that shape, their thickness is about 1/4 their diameter. Melles Griot (one vendor of optical flats) sells ones that are 6 mm (about 1/4 inch) thick, but they're only 25 mm in diameter. For 4 inches diameter, the thickness is 3/4 inch. There's no way 1/4 inch glass is stiff enough to remain optically flat if it's larger than this. Various people use glass plates for lapping things flat, and Lee Valley even sells a piece of 1/4 inch glass the size of a piece of sandpaper, but it's really not flat enough for machine alignment. Just putting a test indicator on a stand, with the indicator point a few inches from the stand, shows a few thousandths change as I move it around the plate. And if I lift it up and look at it nearly on edge, I can see distortion in the image reflected from the plate. I don't even use it for sharpening any more - I use the thicker plate below or a granite surface plate to back up the sandpaper. On the other hand, I have a piece of about 4x10 inch by 1/2 inch thick smoked plat glass, and it's as flat as I can measure (and looks flat in the reflection-on-edge test). This one might be good enough for machine alignment. Dave ------- Date: Thu, 22 Feb 2001 00:22:48 -0500 From: Stan Stocker Subject: Centering the tailstock, several methods WAS:Re: Setting up the Lathe I do a fair bit of tweaking/restoring and rebuilding of lathes so here's my somewhat long winded two cents (S&H included) worth. Using assorted techniques, I have made a number of parts that involve drilling holes to remove most of the center of a shaft, although there is usually 10 to 15 thou wall thickness left. Poking a 5 thou hole in a 9 thou shaft isn't on the list of stunts I've tried, although drilling 1/16 (0.0625) holes in the end of shafts turned to 0.080 is on the list. Indicating the results on a surface plate with a V block showed concentricity to within 2 tenths. Precision Test Bar methods and Gotchas: A precision test bar combined with a tenths reading dial indicator is the best all around, provided you have centers of known quality, or cut a 60 degree headstock center as part of the process. I prefer to cut the headstock center as on old lathes you never know who's done what, where, or to what standard of accuracy. Cutting your own center ensures the point is on the spindle center of rotation. Just don't unmount and remount the newly cut center! Many variables are eliminated by cutting the center. If the tailstock center is higher or lower than the spindle center, watch out for errors introduced by this. If only a matter of a few thou, using a button head on the indicator will avoid the error, combined with using the largest reasonable diameter test bar. If it's more than a few thou fix the problem. Note that some larger lathes have the tailstock 3 thou high when built. I made bars in several diameters to handle just this situation, and to avoid droop in the center of the bar. A 1/4 inch test bar spanning 10 inches is going to flex and droop, a one inch bar won't unless you do something silly, or want to chase far finer than tenths. Note that you can't make a precision test rod for use between centers without a steady rest. You can come close, but the 60 degree hole for the centers really must be bored using the compound, not drilled from the tailstock, while the blank is running on its perimeter. You also need a lathe with several inches more length than the length of the shaft to be bored. Start with some centerless ground stock. Verify it is truly round and dead straight using a surface plate and V blocks. One completed, never spin a test rod on the centers, by hand or under power. If you lightly oil the centers, you can gently turn the bar on stationary centers while indicating the perimeter to satisfy yourself that it is true and straight. The tailstock on the Taig is an odd little beast (no offense here, it is just different). Examine the tailstock center cone closely to ensure no burrs, crud, oil varnish, etc. At least you don't have to sweat indicating the interior of a morse taper or have a standards grade piece of MT tooling known concentric to the axis of the taper! The down side is that if you bugger up the tailstock center, you make or buy a new tailstock ram, or spend some time getting to know your toolpost grinder (on a lathe that can swallow the ram, the Taig can't). Indicating the Tailstock Center: Lacking a precision test bar, or when dealing with a worn lathe, swinging a test indicator from the spindle is a very good way to get things in line. I use this method often for non critical work, it will get you to well under a thou with care in short order. Simply swing front and rear, note the difference, and adjust half the distance. Repeat until dead on or close enough. On a worn lathe, this will give a trustworthy setting to allow the test bar to be used to verify the carriage isn't wandering about on a worn or incorrectly planed/ground bed. Cutting Test Bars (two rings, taper, assorted approaches abound). I reserve cutting test bars (the two rings method) for verifying the overall behavior of the lathe, as this introduces possible issues with loose gibs, cutter wear, bed twist, and the like. It is certainly valid, and is one of several final proofs that the lathe is set up correctly overall. The problem is that you may see a result due to something other than tailstock alignment and try to adjust it out and end up hiding an issue that will bite you later. As the Taig bed is more of a clockmakers style this is less of an issue, bed twist and leveling are not something that usually comes into play. Centering Drills - Not always the same as centering the tailstock center!: If you must center a drill on the spindle centerline, don't overlook swinging an indicator on a bit of drill rod of the same size as drill bit to be used held in the drill chuck. This will allow you to tweak out some of the variation inherent in using a drill chuck. This is particularly useful when drilling a hole that is nearly the size of the shaft to be drilled. Do your best to tighten the drill rod the same as the drill bit to avoid adding another variable into the mix. Another option, slightly less accurate, is to hold a piece of 1/8 drill rod in a collet with about an inch extended. Loosen the tailstock, tighten the chuck on the drill rod, snug the tailstock to the bed, then tighten the tailstock center clamp. Works like a charm, and it's fast too. You can use smaller, but keep your eyes open. 1/16 drill rod likes to flex. To verify nothing moved, release the collet, retract the ram, then try to gently push the drill rod back into the collet. If it hangs, something moved. Go back and do it all over again. It's not close enough - trust me, I tried to kid myself on this once, ended up with a lovely shaft with a pretty 270 degree crescent on the end rather than a concentric hole. As I already had a half an hours work in on the shaft I was rather ticked at myself. Don't be surprised to find that the drill chuck doesn't snug to the same center as the tailstock - a few thou variation can trash a small bit in a hurry. It also won't snug to the same center through its entire range. Like the three jaw, there is variation due to the tolerances of the manufacturing process. You will still see this on Albrecht drill chucks, just a lot less than on a $10 utility grade chuck. This is another reason much precision work is done with collets rather than chucks. Stan ------- Date: Thu, 01 Mar 2001 19:03:25 From: batwingsx~xxi-plus.net Subject: Re: indexing propeller hub At 09:40 PM 2/28/01 -0600, you wrote: >I did some indexing with the 3-jaw and 4-jaw mounted to the headstock at >one point. I did it >by using a bubble level straddling two of the jaws of the chuck. Nice thinking but the easy way to index with chuck is to set a stop between a jaw and bed. It's solid, stable, accurate and quick. The stop needs to be square on ends and the jaw should rest on it at outside corner, IOW, jaw needs to tilt downward to the stop. Regards, Hoyt ------- Date: Fri, 2 Mar 2001 11:34:07 -0800 From: Brian Pitt Subject: Re: Run Out: $64 question On Friday 02 March 2001 09:18, you wrote: > When measuring run out. Is it the displacement from the center > line or the total swing. That is if I put a indicator on a rod > in a chuck and it goes from +.001 past center to -.001 past center as > I rotate the chuck for a total dial movement of .002 is the run > out .001 or .002 it usually gets called out as TIR (total indicator reading) so the example would have a concentricity of .002 TIR Brian ------- Date: Tue, 06 Mar 2001 15:35:36 -0500 From: "Rich D." Subject: Re: how to find center of a circle bar stock david albert wrote: > Once again I hope this is not a stupid question, but how do you find > the exact center of a circle. For example, I want to drill a hole in > the exact center of 4" diameter aluminum bar stock. I tried a method > used in geometry class back in high school using a compass. > Essentially drawing 4 arcs and drawing a line from the intersection > of the arc points creating two perpindicular lines. I was off by > about 1mm. Is there an easier more accurate way? David, even if you were off a mm, it left you a nice small scribed box to visually center a center punch. Just a good as dead on. For "exact" work, you need a surface plate and surface gauge set to the radius, or the nearest sufficient equivalent. If you have a vertical mill, set the stock vertical and indicate the to center to get the quill dead on. With a lathe, set the stock to indicate zero runout and center drill. "Indicating" is with a DTI (dial test indicator), from previous discussions. Rich D. ------- Date: Tue, 06 Mar 2001 12:35:20 -0800 From: Alan Marconett KM6VV Subject: Re: how to find center of a circle bar stock David, use a center-finding head for a machinist's square. Looks like a 'V', with the blade of the square going through it. Scribe a line, rotate 1/3, scribe again, and you have the center where they cross. Rotate and scribe again, and your third line should ALSO intersect at the center! You NEED a square in your shop! ------- Date: Fri, 13 Apr 2001 13:27:35 EDT From: catboat15x~xxaol.com Subject: Re: dumb question"test bar" In a message dated 4/12/01, chad_gassawayx~xxhotmail.com writes: > what is the correct term for the bar you put between centers to align I think that "test bar" is the right name. I have never seen one in a catalog so I think most machine shops make their own. Get a good chunk of some material (Alum, Brass, Steel, whatever you may have around) Put it between centers and turn it with a ring close to the headstock, remove put the other end at the headstock and turn another ring the same size (use your graduated collars to make it the same.) Now you have your own test bar. This is assuming you have already used the pinched scale between centers to get the alignment close. John Meacham High Desert of California, Palmdale, Littlerock. ------- Date: Sat, 14 Apr 2001 20:25:46 -0700 From: "Nicholas Carter and Felice Luftschein" Subject: Re: Flycutting [TAIG MILL BUT TIP APPLIES TO OTHERS] From: > I am flycutting some 7075 aluminum and the overlap leaves about > a .001 ridge. I am taking passes at .001 in depth. Is there > any way to get rid of that ridge while cutting or is this a normal > occurance. You will have to excuse my ingorance I am a complete newbie > to this. Any help will be greatly appreciated. Thanks, Phil Warden This can be caused by the head being out of alignment to the y-axis. (assuming that you are taking passes along the x-axis and then moving over with the y). This has come to light recently with the new mills, as the dovetail plate which mounts the headstock to the mill slide isn't perfect and on large diameter cuts with a flycutter (or when tramming in the y-axis, which can mistakenly lead you to think the column is out of alignment - it usually isn't) Try shimming the dovetail plate to correct this. This can be checked by sweeping the y-axis with a dial indicator in the headstock. See our web pages http://www.casco.net/~felice ------- Date: Sun, 15 Apr 2001 03:39:27 -0000 From: airwardenx~xxhome.com Subject: Re: Flycutting Actually I am making my passes on the Y axis and transversing on the x axis. If I put a dial indicator in the spindle I get just a hair over .001 runout in a 2" diameter circle. ------- Date: Sun, 15 Apr 2001 02:54:23 -0500 (CDT) From: Tom Benedict Subject: Re: Flycutting On Sat, 14 Apr 2001, Nicholas Carter and Felice Luftschein wrote: > Try shimming the dovetail plate to correct this. This can be checked > by sweeping the y-axis with a dial indicator in the headstock. Thank you! So far my Y axis has been dead-on, but I've been dreading the day I find out it isn't, for fear I'd be shimming the whole column (NOT my idea of fun, OR of a good idea). Hadn't even occurred to me to shim the dovetail. DOH! Tom ------- Date: Sun, 13 May 2001 22:31:55 -0700 From: "Nicholas Carter and Felice Luftschein" Subject: Re: Re: Indicator point thred size? Paul R. Hvidston wrote:> Ballendo, > The replaceable tip thread size for most/if not all AGD style > indicators is 4-48. The other one is M2.5. You're right - I should remember to wait before posting with my faulty memory - I even bought a 4-48 die for just such a reason. See our web pages http://www.cartertools.com/nfhome.html ------- Date: Fri, 18 May 2001 13:09:00 -0500 (CDT) From: Tom Benedict Subject: Re: metrify inch by inch? On Fri, 18 May 2001, Nicholas Carter and Felice Luftschein wrote: > Not really, you can do one of two things: > 1) redraw any plans you have in a Cad program and change the units from > metric to english > 2) mount metric dial indicators on all axis. I heartily recommend #2. I don't even look at my handwheels any more (though I'm using English dial indicators.) I finally got my copy of "Building the Shay" from Amazon (after three months of biting my fingernails.) It's all in metric units. For the mill work that's not a problem since I'm using the CNC mill, for which units are a toggle. But for the lathe work, a metric set of dial indicators was exactly what I was planning to do. (And before anyone mentions that the Shay is likely outside the work envelope of the Taig, yeah, I know. I'm planning on scaling it down.) Tom ------- Date: Tue, 22 May 2001 14:38:31 -0400 From: "William Rutiser" Subject: Re: Manual Indication Here are a few things I have used... Get a straight round rod that is easy to chuck in the spindle. A drill blank or dowel pin that fits a collet would be a good choice. Prefer a nice round dimension that is easy to divide by two. Nip a strip of paper lightly between the rod and work. Try to establish a consistent feel as you withdraw the paper. You now know a relationship between the spindle axis, the work, and the leadscrew dials. You could use this at the ends of your vice jaw to set it parallel to the table travel. Or if you raise the spindle and move it toward the work by half the rod's radius plus the thickness of the paper, the axis will be aligned with the edge. The "sticky pin" is another old dodge that you may find useful. You need a common sewing pin and a small piece of something like modeling clay, Blue-tac, or a slow drying putty. Use the clay to stick the head of the pin onto the spindle, chuck, or tool, with the point generally on axis. Now run the spindle at a modest speed. The pin's point will traverse a small circle. Use a smooth piece of metal to push the point into the axis. This arrangement has some interesting physics. It is easier to do than to describe. When the pin is centered, you can use it to align the spindle with an edge or a scribe mark. A magnifier helps. Another edge finding trick... Stick a bit of paper to the work with oil or saliva. Now slowly advance a running cutter toward the paper. When the cutter touches the paper it grab it away. The cutter is now one paper thickness from the work. Cigarette paper is traditional for this. It's about 0.001 inches thick and consistent. Bill Rutiser ------- Date: Wed, 23 May 2001 01:18:22 -0000 From: ptolemyx~xxbellsouth.net Subject: Re: Manual Indication Thanks for all the suggestions -- this is a great group! The creative use of paper as a measuring device was something that I didn't think of. Some of the tricks I figured out are similar to some of the suggestions. (In case it's not obvious, ALL the follow steps are done with the milling machine turned OFF.) Here's how I find the center of a hollow cylinder: 1) I have some small biological specimen needles; these made of spring steel precisely 0.012" in diameter, and are extremely straight. 2) attach one of these to the mill head at a known distance from the center leaving about 5mm sticking down. 3) Lower the needle into the cylinder about 3/4 of the way. 4) Carefully crank the x-axis until the needle begins to touch the edge of the cylinder. At this point, the needle will bend slightly. This causes the lower part of the needle to deflect away from the wall of the cylinder and you can see a tiny gap open up. 5) Back off the x-axis until the needle just straightens out (the gap closes) -- conveniently this also takes up the backlash. 6) At this point I do the math and crank the needle to the center (taking into account needle diameter, position on the head, and cylinder diameter). 7) Repeat the process for the y-axis and then again for the x-axis. Now the needle is centered and the position of the head can be computed. Also -- this is probably a well-known trick -- I've discovered how to use shim brass foil to exactly position the cutter on top of a hollow. I cover the hollow with a little piece of brass foil , then carefully crank the (non-rotating!) head down. If the angle of the brass to the light is right, you can see it distort just when the head presses against it. You can then pull it out from under the head and account for its thickness. Maybe it's just beginner's enthusiasm, but I enjoy tinkering with the mill itself almost as much as I enjoy making things with it! Neil ------- Date: Wed, 23 May 2001 02:39:57 -0000 From: yahoox~xxaffiliated-products.com Subject: Re: Manual Indication To locate the tool to the work piece: A very fast and accurate way is to lower your spindle and it's tool off to the side of, but in the same Z plane, as your work piece. Using calipers measure from the shank to your work piece in X and then in Y. Then raise Z and move the table the amount you measured. For Z use the caliper to measure from the bottom of your tool to the top of your work piece. That's it. To find the center of a work piece, measure two opposite sides, and move your table to the center of the two measurments. This technique is as fast to do, as to say. It lets you keep the tool in the spindle. Is easy to verify by moving the table a known amount, past the work piece, and repeat the measurement. It can be accurate to 0.001", with a little practice. By the way, it is usually useful to machine a reference point on the work, as the first step. (Cut one of your corners or drill one of your holes). If this first cut can be roughly located, then it become the measuring point, rather than the tool, from which all the above mentioned measurements are made. Reasonable calipers can be had from MSC or Enco for under $20. The hardened measuring points of calipers are great to directly scribe onto the work piece. (I use a black marker first and then use the calipers to scratch the mark.) I had my calipers surgically attached to my right wrist. Buck ------- Date: Wed, 23 May 2001 23:58:22 -0000 From: ssmithx~xxserena.com Subject: Re: Manual Indication I use a home made continuity checker between the spindel and the part. With spindle stopped or running at a slow speed and just as the cutter rubs the part the continuity blinks or lights up. It use an LED mounted in a test probe with a 1K resister. I use a 9 volt battery with one end connected to the motor mount screw and clip the probe lead to the other terminal of the 9 volt battery. (Make sure the polarity is correct.) I put the probe point on the part. The 9 volt battery sits on the motor controller held between the power cord and the motor. Steve ------- Date: Fri, 15 Jun 2001 09:26:51 -0000 From: J.C.Beechx~xxshu.ac.uk Subject: Re: Dial indicator mount? --- In taigtoolsx~xxy..., "Eric" wrote: > I need some ideas for a dial indicator mount to indicate carriage > travel. I have a 2" dial indicator that I need to get set-up. Any > help or ideas would be greatly appreciated. Thanks, Eric Not so much help as advice for beginners going this route. I have always found with mechanical dial indicators I have owned that the scale is never linear, i.e you always get errors due to the rack and pinnion or just plain wear. Be very cautious of using a dial to take readings, they are really only intended for working to a zero point, i.e cutting to a shoulder etc. The digital gauges on the other hand have a very precise scale for the sensor and these are a good option for small measurements. I suppose the point I am getting at, is you don't need to use a long travel dial, for my use a steel rule and a pointer do for traversing the bed, the dial is used just to zero in for .001" accuracy. Anyone that can point me to cheap, accurate dial guages with 1" travel I would be eternally gratefull, but I am talking errors of less than .003 over the entire travel, and so far only digital has met the challenge. Joules ------- Date: Tue, 19 Jun 2001 09:33:01 -0700 From: "Dave Engels" Subject: RE: Graduation sensitivity of a machinist level to level a lathe From: Steve Leftwich [mailto:sleftwichx~xxwvutech.edu] >>From the information I have read for the leveling of a lathe, it says to use a "level at least 6" long that shows a distinct bubble movement when a .003" shim is placed under one end." In looking at buying a level, for example a Starrett 8" Machinist level Model #98-8, it lists the graduation sensitivity of .005"/ft. Is that adequate? Steve L. << Steve, a 0.003" shim under a 6 inch lever arm produces a 0.03 degree angle. This is a measure of the sensitivity of the level. A 0.005" per foot is 0.024 degrees, which sounds like it is better than requirement. Hope this helps Best, Dave ------- Date: Wed, 20 Jun 2001 00:30:19 +0000 From: Jon Elson Subject: Re: Graduation sensitivity of a machinist level to level a lathe > > graduation sensitivity of .005"/ft. Is that adequate? << It's better than nothing, but a more sensitive level is preferred. I have a Soviet-made master precision level that is graduated for .00075" / foot. The imperial-calibrated M.P.Levels are calibrated at .0005" / foot, or sometimes .0005" / 10 inches. There are import versions of this listed in most of the machine tool supplier catalogs, and they often have specials in the $89 range. Jon ------- From: Gordon Reithmeier Date: Tue Jul 10, 2001 4:25 pm Subject: Re: [sherline] Indicator/.0005 Joe Baker wrote: >>> This question is for anyone that cares to reply. How do I read an indicator that shows .0005 on the face and has 10 increment marks between 0 and 5. i do well with the mike and venier but I havent been able to figure thi little puppy out. Regards, Joe <<< Each increment = .0005(half thou), 10 increments = .005(5 thou.) Gordon, Toronto ------- Date: Tue, 21 Aug 2001 20:52:22 -0500 From: "Skip Evans" Subject: Centering on a 4 jaw chuck I learned a valuable lesson this evening. When centering a piece of square stock in a 4-jaw chuck using a dial indicator be sure to watch the revolution counter as well as the large needle. I eyeballed everything, then put the dial indidcator to it. All looked well as far as the large needle was concerned. I drilled the hole and realized I was off. What could have gone wrong? Well, I was exactly 1 revolution off. I guess I will have to remake the part. ------- [NOTE TO FILE: This subject was discussed in more detail and gathered in this site's file "Turning Tips Metal".] ------- Date: Thu, 23 Aug 2001 20:22:34 -0700 From: "Bob May" Subject: Re: Centering on a 4 jaw chuck The problem is that dial indicators all have a multiply turning needle. I use a test indicator always and that only goes around once and also allows for trailing (edge pushes up the ball while pulling on the instrument) edge measurements which will keep the measuring instrument from moving. Besides, dial test instruments are a lot more accurate than the run of the mill dial indicator. Bob May http://nav.to/bobmay ------- From: "Robert" Date: Fri Aug 17, 2001 8:56 pm Subject: Starrett Last Word Instructions I just purchased a Starrett Last Word Indicator, which I have been able to clamp to the Sherline Mill and I am now in the process of making a permanent fixture to give the Last Word something on the mill to attach to. However, there were no instructions with the Indicator and it has over six different accessories/attachments. I have been able to figure out a couple of them but I don't have a clue about how to use the others. I've searched the Starrett web site and searched the Internet but cannot find any instructions for the Last Word. Does anyone have instructions on how to use the attachemnts/accessories? I am mystified... TIA Robert ------- From: "Rich D." Date: Fri Aug 17, 2001 1:34 pm Subject: Re: [sherline] Starrett Last Word Instructions Robert, there are none. It's just common sense and a need to set it up with what's available. Look at what is there and see what can be used. It is a puzzle, as most machining problems are. You will learn, in time, to figure things out as the need arises. There are other accessories you can borrow from other sets. The Last Word has to be manually reversed with the little switch on the side of the body. The tip (stylus) is held in a serrated seat. To change its position, just force it to the stop and push more to jump it to the next position. RichD ------- From: "Bill Rutiser" Date: Sat Aug 18, 2001 10:25 am Subject: Re: [sherline] Starrett Last Word Instructions > I just purchased a Starrett Last Word Indicator, which I have been > able to clamp to the Sherline Mill and I am now in the process of > making a permanent fixture to give the Last Word something on the > mill to attach to. The lower screw holding the motor bracket to the spindle housing is a convenient place to attach an indicator mount. Bill Rutiser Gaithersburg, MD ------- From: ptolemy... Date: Sat Aug 18, 2001 11:58 am Subject: Re: Starrett Last Word Instructions I've found it handy to look through machining books like "Tabletop Machining" and "Machining Fundamentals", or magazines like "The Home Shop Machinist" or "Machinist's Workshop." You can find interesting examples of attaching and using DTI's (often Last Words). Some of the setups are novel and ingenious! -Neil ------- From: "Joe Baker" <855_1071...> Date: Sun Sep 2, 2001 4:58 pm Subject: Re: [sherline] Starrett Last Word Instructions The starrett catalog gives you a brief description of the uses for the last word indicator. They will mail you one if requested ------- Date: Mon, 27 Aug 2001 17:29:49 -0000 From: ptolemyx~xxbellsouth.net Subject: Interesting Rotary Table Accessory I made a simple but useful accessory for my rotary table today. The problem was, I needed to be able to center a part with an existing #61 drill hole on the rotary table so the hole was on center. I would normally do this by centering the table under the chuck, chucking up a #61 drill bit, and then using this to center the part. Unfortunately, other considerations in the setup made this method unwieldy, and I was making more than one part. So I did this: I turned a scrap piece of aluminum so that it fit snuggly into the center hole in the rotary table and flush with the surface. I drilled a #61 hole in this. Now I can center the part by passing a #61 drill bit down through the existing hole and into the hole in the aluminum part. The very slight amount of "play" is not an issue for my application. Neil ------- Date: Mon, 27 Aug 2001 13:01:15 -0700 From: Alan Marconett KM6VV Subject: Re: Interesting Rotary Table Accessory Hi Neil, just a thought, but why not scribe an accurate cross hair on your "plug", and use a "wiggler" center finder? If you are not familiar with it, the one I am referring to has a 1/4" shank that you mount in the spindle collet, and has a sharp needle point with a ball end that mounts into the shank's receiver end. The spindle is turned slowly, and the sharp needle point's wiggling is "trued" by lightly pressing it's point over with the end of a short piece of rod. Once trued this way, the needle point is "dead on", and you can move X & Y to align it to the cross hair. Drill bits tend to deflect, and a #61 could deflect considerably. OR- If the hole were bigger, a metal dowel pin might work a little better for you. Why not accurately turn the 3/8" - 24 (?) thread that the table takes on a 3/8" rod, and turn the other end down to 1/4", to fit a collet. Then you could "hang" the table from this rod, clamp it down, release the collet, and remove the rod. I am familiar with this task, I have a rotary table too. I think this could work! Another way would be to use a Test dial indicator (Last word) to "indicate" off the clamped work. HTH Alan KM6VV ------- Date: Mon, 27 Aug 2001 20:51:23 -0000 From: ptolemyx~xxbellsouth.net Subject: Re: Interesting Rotary Table Accessory Thanks, Alan. Those are good solutions for quickly centering the table. I like the rod and collet approach -- sounds like maybe I have a project for next Saturday :) In my current case, the spindle was being indicated on a different part of the part. The #61 hole was the center of the axis of rotation. My ad hoc accessory let me quickly move parts onto the setup in "assembly line" fashion. But you're right, the bit does deflect quite a lot and I have to use care not to stress it too much. I am definitely sacrificing some accuracy to setup speed. Neil ------- Date: Mon, 27 Aug 2001 15:11:51 -0700 From: "Craig Libuse" Subject: Re: Re: Interesting Rotary Table Accessory > I have been wondering why there is not a hole all of the way through > the center so that you can push things out from the rear. Joe feels that a hole all the way through the rotary table leads to trouble when chips fall through and get under the rotary table when it is moved around on the mill, leading to a non-flat setup. Some watchmakers have requested a through hole, so we have compromised by making the hole deeper but not quite all the way through. It is not a hardened part, so anyone can easily drill through your own if you have need for a through hole. If you do not need the threaded insert, the hole can be opened up as large as 1/2" without getting too near the inner race of the bearing. The threaded hole is used in the production process to locate the part for one of the manufacturings operations, so we need to keep it the size it now is unless we were to change the whole way we now make the table. Craig Libuse Sherline Products Inc. ------- Date: Thu, 30 Aug 2001 23:40:06 -0400 From: Thomas Gilmour Subject: Re: Interesting Rotary Table Accessory Neil & all, I had a project recently that required accurately centering the rotary table to the spindle. I made an adapter similar to what Alan proposed with a 3/8-24 thread and a hole bored through the center to accept a pin. I found that the accuracy wasn't as good as I wanted, possible due to the play in the thread. So what I ended up doing was turning a plug which fit snugly into the hole of the table above the threads. I bored a 1/4" center hole in this plug to snugly fit 1/4" drill rod. Clamping a short piece of drill rod in a collet allowed very accurate centering of the table. After clamping the table down the drill rod can be removed and replaced with a centering pin of any diameter needed which has a 1/4" end to fit the plug still in the table. Tom ------- Date: Sat, 15 Sep 2001 23:33:26 -0400 From: "Carol & Jerry Jankura" Subject: RE: Dial (test) indicator questions [IN USE ON ALUMINUM SHERLINE EQUIPMENT] 1. Magnetic indicators will NOT stick onto most sherline components, including the bases. They will stick onto the steel surfaces (ways). 2. Many of us have glued some ferrous sheet to the mounting board of the Sherline tool for the express purpose of holding magnetic bases. 3. Depending what you want to do, either can be the most useful. For example, you can mount dial indicators to allow you to accurately determine the position of the crossslides on the mill. You might use the Test Indicator to center the mill spindle on a locating hole in a workpiece. Which task you are most likely to perform determines which of the gauges you should buy first. Note that I said FIRST, because you'll eventually want to have both. Carol & Jerry Jankura Strongsville, Ohio ------- Date: Sun, 16 Sep 2001 20:12:50 -0500 From: "Bad Brad" Subject: Re: RE: Dial (test) indicator questions I have seen some people mount a steel plate onto the base board that the lathe and mill are mounted to. If you own a sherline lathe with a brass way, the magnetic indicator base will not work either. I have found when working on centering stock, in what ever chuck or face plate you are using, remove the magnetic portion of the test indicator base and hold it in the tool holder on the sadle. This is a very rigid set-up. An extra tool holder either made up or purchased will speed up set time up as well. For centering stock in a four jaw I use a Starret Last Word; they are small, mount in a tool post perfectly and can be purchased used with most of their attachments, cheaply ($10-$35). Forrest ------- Date: Wed, 07 Nov 2001 07:38:33 +0000 From: Jon Elson Subject: Re: dial vernier caliper question Steven Harris wrote: > My dad had me make some small part for him. I made them and mailed them > off. He e-mailed me back saying that they did not fit because they were > .001" too big. I was confused because they were exactly the size he > specified (I had triple checked each part. You have to make quality > parts for dad.) After some discussion back and forth we figured it had > to be my measuring device ( all of 7 identical parts were exactly .001" > too big). So I took a look at my trusty dial vernier caliper. I found > when the jaws were closed I could see light coming through them in the > area I usually use to measure. Checked the gap and it was .001". So do > these things wear out? I take good care of my measuring tools always > storing them with the jaws open, making sure that they are clean, > checking the zero before each use and storing them safely. Or is this > something that was present when I purchased them 12 years ago? I'm > thinking that it will be something I check on my next purchase. Dial calipers aren't all that accurate. It is also fairly easy to ding the measuring surfaces or the tips of the OD jaws. If you see light evenly along the length of the jaws, there is a ding somewhere. If there is light only at one end, then the jaws aren't parallel. Since you zero'ed the caliper and then made parts .001" oversize, that pretty much sums up the fact you have a ding somewhere. A .001" raised spot from a sharp object scraping the jaws is pretty hard to find. Any time I make a precise measurement, I wipe the jaws with my fingers, from the middle outward each direction, to remove all tiny grit particles. Cloths and paper towels leave dust particles, so clean hands seem to be the only thing that works. A fine india stone can be used to remove the tiny raised mark if careful wiping doesn't fix it. If the problem is right at the tip of the jaws, you can file the jaws down a little or use the side of a bench stone. Obviously, do this very carefully, and then even up the two jaws. For more precise measurements, you need a micrometer, they are much more accurate than a caliper. Jon ------- Date: Wed, 7 Nov 2001 02:54:30 -0500 From: "Darryl Urcheck" Subject: Re: dial vernier caliper question I have found it's useful to have a friend periodically double check a part with his micrometer, using it as my gage, so to speak. Also, I use Vernier calipers for rough measurements, but .0001 micrometers for finer work. Friends criticize me for being too precise, but hey, I'm not in a hurry: measure twice, cut once. This is especially true on some engine work. We have come a long way from the days when a 1/64 steel rule was used for engine work. Darryl ------- Date: Sat, 08 Dec 2001 12:55:30 -0500 From: ron ginger Subject: Re: DRO I personally dont like the Sherline DRO- it is really a turns counter on the lead screw, it does not sense the actual table movement. It does have software compensation for backlash, but you need to measure the backlash accurately or else the readings wont be accurate. And if the backlash varies along the screw (and Im sure it will with wear ) then it wont be accurate. I suggest you buy 2 digital calipers, which can be bought for as little as $40-50 on various sales. Make a couple brackets to attach them to the tables. You then have a direct measuring device, most have zero reset and will do metric to inch conversion. And if you make the bracket well the caliper can be removed quickly and used as a caliper. The only drawback to this is that the two readouts won't be beside each other on a nice display. But you save at least $200 and get a device that is a real DRO, not a wheel turns counter. Sorry to be negative about a Sherline product, but IMHO this one could be better. ron ginger ------- Date: Sat, 08 Dec 2001 18:33:12 -0000 From: "n2562001" Subject: Re: DRO Ron, I can`t comment on the Sherline DRO since I have not used one other than play with them at show`s. However a while back I did clamp a Mitutoyo 6" Digital caliper to my Sherline mill and try what you have suggested. It seemed to work Ok until after about five hours of operation when it died. When I opened the unit up it had several damaged circuit board connections that appeared to caused by machine vibration. Since then I have talked to two other people who have tried this with the same short life results on small mills. I have a extra Mitutoyo DRO Quill travel unit I may try one of these days and see if I have better luck. Just my experience; thought it may be of interest. Have Fun Jerry Kieffer ------- Date: Sat, 8 Dec 2001 12:20:04 -0800 From: "Yasmiin Davis" Subject: RE: Re: DRO Has anyone tried this? The Bridgeport spindle down travel measuring devices are cheap and made for this. It would seem that they should work well and they even come with the mounting brackets. Yasmiin ------- Date: Sun, 09 Dec 2001 17:40:01 -0500 From: ron ginger Subject: Re: DRO I have had a caliper on my Bridgeport quill feed for a couple years with no trouble. Im sure it gets as much vibration as any Sherline size machine. Wholesale Tool (stores in several cities and on the web) sells what appears to be the same mechanisn as a caliper, just without the measuring arms on the ends, and with brackets to mount is on a mill. They offer them is several lengths, up to about 18" as I recall. It is important with any DRO to be sure the table travel does not bind or jam on the caliper. I have a Mitutoyo DRO on my Clausing mill, and the installation instructions were very clear on the importance of alignment. Maybe the early caliper failure came from a misalignment? ron ginger ------- Date: Sat, 15 Dec 2001 19:37:58 -0500 From: ron ginger Subject: DROs and Calipers I have had a caliper attached to my Bridgeport Z axis for several years with no trouble. This is an actual caliper which I cut down to fit. There are also similar packages sold with brackets to fit a mill. All 'real' DROs have an electonics package in the reader head. I have a Mitutoyo low-end unit on my clausing mill and it has exactly the same mechanism as the caliper, with read heads attached to the table. It has been inuse for 5 or 6 years with no trouble. So, I see no reason a caliper wont work just fine as a DRO on a Sherline. I suspect the warning against their use is by 'armchair experts' that are speculating on things that could happen, not real experience. On, The Sherline DRO has an encoder in the reader unit, which is also electronics, so if vibration kills electronics how do they keep working? ron ------- Date: Mon, 17 Dec 2001 09:27:56 -0800 From: "Craig Libuse" Subject: Re: DROs and Calipers >So, I see no reason a caliper won't work just fine as a DRO on a Sherline Ron, our experience was based on trying one and having it go bad. Jerry Keiffer had the same thing happen. Perhaps we both got bad units and gave up too early, but the experience was not theoretical. Maybe the larger mass of the Bridgeport lessens the effect of vibration on the caliper. The Sherline encoder is a simple optical unit that senses the position of teeth on a star gear in the handwheel unit. The circuit boards are in the control box, which is a separate unit. Some people have mounted their control boxes on top of the speed control with Velcro or double/stick tape as a convenient place to read the output and keep the cables out of the way, and I haven't heard of a failure yet. Could be the tape insulates some of the vibration or maybe our larger circuit boards and chips are a bit more sturdy than the tiny ones used in the calipers. Craig Libuse Sherline Products ------- Date: Mon, 17 Dec 2001 19:29:51 -0000 From: "terry6453" Subject: Re: DROs and Calipers I turned my nice new mill on and it does not seem to vibrate nearly enough to damage normal electronic components (I am a reliability engineer). Electronic circuit boards survive in car engines, wrist watches, missiles ... with no special problems. The mill "should not" be any problem at all. My first thought is that the caliper was just "a bad one". However, it appears Craig as seen a bad "two" now, which is odd. If the calipers really are being killed by the mill environment, there are some special weak spots to suspect. 1. Battery connections in calipers are a bit none standard and tend to use the stainless steel body of the caliper that may have contact problems. 2. The LCD screen connections may be susceptible to vibration. This type of connection is well understood but if the screen design in the calipers is unusual someone may have done something creative and messed it up. 3. I assume they use a magnetic head and strip to determine the position in these things. Vibration may confuse the electronics if the head vibrates over a mark and seeds high speed signals back to the electronics. This may lock up the electronics but removing the batteries and reinstalling them should clear the problem if simply turning it off and back on does not. This could be a real big problem if vibration causes the reading to drift as the caliper gets false movement signals. 4. The magnetic pickup could be failing if it was not made well. I assume it is a Hall sensor, which should be indestructible. If it is a coil of wire like a tape recording head it may have a weakness. 5. Static electricity could be zapping the electronics. This is a very big possibility. 6. The buttons for the controls could be having a problem with vibration especially if their design is sort of odd. 7. The batteries ran down ;-) I would think removing and replacing the batteries should restore the caliper to life. If both failed calipers were the same brand and type, they may have some common defect that does not affect other types. I looked at my Starrett 723 and a few digitals I found at work and they look pretty tough. I don't feel like taking apart the Starrett since it is not broken (yet :-)) but maybe I'll pick up a cheap caliper and play with this. I have a nice wide-band G-sensing vibration probe and FFT scope I'll hook to the mill tonight to see what the vibration looks like. I doubt if it will show anything but it sounds fun to do and will help me justify those expensive toys too :-)) If you still have the broken calipers, try removing and replacing the batteries and checking the batteries to be sure they are good. If you can tell us what went wrong with them (dead, display gone nuts, frozen, etc.) that may provide clues too. Of course, using a caliper is only one of many options, but it is attractive in some high precision or inexpensive applications (especially if one already has the caliper). Mounting the darn thing is another challenge... Cheers, Terry ------- Date: Mon, 17 Dec 2001 13:57:06 -0600 From: "Bad Brad" Subject: DROs and Calipers The main problem with the hand-held calipers is the fragile pickup for position. Wheather the position pickup is magnetic or optical the amount of vibration to knock these parts out of alignment is not much. I can tell you (Ron) that the people you refer to as "armchair" people are far from it, their experiences are learned first hand and not made up. I would not let any of the stuff written in these (Sherline or Taig) news groups stop anyone from trying things for themselves. Usually the words can't or shouldn't are invitations for doing it anyway. Forrest ------- Date: Tue, 18 Dec 2001 03:13:06 -0000 From: "terry6453" Subject: Re: vibration - DROs and Calipers I checked out the mechanical resonances and vibration of my Sherline 5400 mill to see if there was anything there that may hurt an electronic caliper. I hooked up a Tek3012 Scope with FFT and a Measurement Specialists 0-20kHz accelerometer to my Sherline mill. A just taped the sensor to the back of the mill vise as shown. http://hot-streamer.com/temp/Sherline/Pc170002.jpg http://hot-streamer.com/temp/Sherline/Pc170003.jpg At first the electrical noise was messing with the tiny sensor's signal. The plastic case that houses the mill's electronics does not shield the electrical switching noise from the electronics well. A transistor radio picks up the noise nearby but it goes down fast as the radio is moved a few feet away. Practically, this noise is not of much of a concern but it could be a factor to the damage reported to digital calipers. One may want to insure that the caliper and the metal frame of the mill are electrically connected (grounded). The noise is mostly radiated like an antenna, so a simple grounded foil shield reduced it enough to get a good scope reading: http://hot-streamer.com/temp/Sherline/Pc170001.jpg A metal shell around the electronics and perhaps a little bypassing would stop this noise, but it probably does not matter unless you are trying to do something strange like this. So I turned the mill speed up and got the following: http://hot-streamer.com/temp/Sherline/Tek00000.gif The yellow shows the raw vibration from the sensor. 7.9 mV is equivalent to 1 G so we have about 0.89 Grms of vibration. That is very small and will not hurt anything. The red line is pretty neat. It is a graph of the frequencies of vibration. It shows that the vibration is almost entirely made up of 8 frequencies. The left side of the graph is 0Hz with every major vertical line representing 250Hz. So reading them off, it looks like there are resonances at: 120, 240, 350, 400, 475 and then another set at: 1160, 1200, 1230 Hz. I will leave in to mechanical types to decide what causes these but "I" would guess that the low frequencies are from the longer metal parts and the high frequencies are from the smaller parts (or dimensions) like the vise. I wonder if the surfaces were never parallel, like in a stealth fighter, if that would reduces these? Smooth rounded surfaces might also like in those big Bridgeport mills (but even they have big square tables...). I suppose by knowing the speed of sound in aluminum and the dimensions of the mill's features one could find where these resonances come from. Stuff like that makes my brain hurt so I'll pass :-)) Even the highest resonance here is only 0.34 G so nothing is going to hurt a caliper. With the foil, I could not run the mill in an actual situation. However, those vibrations are not inherent in the mill but in any vibrating object. Thus, if those vibrations break a caliper, so will mounting it to all kinds of other things. You just need a better caliper... So I hope I didn't loose everyone :-)) but the bottom line is that the mill does not vibrate oddly or do anything it is not supposed to do. There is nothing here that would hurt a caliper. If one mills things that knock the mill around and cause a lot of pounding, that may be different. However, I would think that is a caliper problem not a mill problem. The electrical noise "could" be a factor but simply grounding the metal frame of the caliper would stop that from being a concern (It may also cure any static electricity problems). I doubt it would hurt anyway but the electrical noise and spikes are pretty strong. If I have not bored you to death already :-)) The accelerometer uses a micro machined lever arm. It uses capacitance to sense the tiny arm's position to determine G force. If you hold it upright it measures 1 G, if you turn it upside down, it measures -1 G. Lots of high tech there and it is really cool! FFT graphs like the above can be used to inspect aircraft and other high importance assemblies. If some major part is loose, the graph will show it as the peaks moving around or being missing. Good parts should all have exactly the same graphs. Some people can hear resonances like the above and pick them out by ear. I imagine you need perfect pitch or something to be really accurate but I guess we have all heard strange whines in cars and such which is the same thing. Some people can listen to machines and determine that something is wrong when others can't. They are simply trained to hear the "right" noise. Cheers, Terry ------- Date: Tue, 18 Dec 2001 08:28:17 -0800 From: Mark Fraser Subject: Cheap calipers Having owned 4 of these for some years, my armchair opinion points toward the battery contacts. If vibration will affect anything, it might just cause enough abrasion of the crappy plating to make contact somewhat intermittent. I've had some "failures" in normal use (or non-use or misuse) that miraculously fixed themselves after I cleaned up the batteries and contacts. The technology is CAPACITIVE, not magnetic. Little rectangles are etched into copper clad FRP (printed circuit board) with dimensions and spacing to allow similarly dimensioned sensor electrodes in the caliper head to detect transitions up / down. Spacing is sorta like vernier scales - small differences between spar and sensors. All in the very old (1990) Circuit Cellar INK article. Someone who became a legend in RCM once published an article on making very long spars for cheap calipers, for use as DRO for larger machines. Previously mentioned, but worth another mention, is the Mitutoyo spar, which most likely uses their digital caliper technology that has been so widely copied in the cheapies.... /mark ------- Date: Tue, 18 Dec 2001 20:32:59 -0500 From: ron ginger Subject: Re: DRO and calipers Thanks Terry for the detailed analysis. One of the things I love about these e-groups is no matter what the topic someone with real serious expertise always pops up when you need it. All of the calipers Ive seen use a capacitive effect for the position sensor. The fixed 'scale' is a piece of PC board with a pattern of rectangular copper areas on it. The copper pads are about 0.2" x 0.4" The read head is an IC chip mounted to slide a fixed distance off the copper pads. The copper pads are covered with a plastic material that provides insulation and protection from dirt, etc. An article in an early PROJECTS IN METAL described this in detail, including the description of a very long scale the author made by CNC engraving a piece of PC board stock. I would guess the main reason one of these would fail would be the simple rubbing of the read head over the scale. On a mill they would likely get more 'mileage' than as a caliper. I've had my Mitutoyo DRO with this mechanism in use for several years now with no indication of trouble. In today's mail I received a flyer from Wholesale Tool with an ad for their line of "Machine scales' These are clearly the mechanism of a caliper, but just a plain metal scale, no hooks on its ends. They offer a model with the LCD display both horizontal and vertical, and in sizes from 4" to 40" long. The 4" long unit is US$44.50. The 12" is $76. So for just under $120 you could have 2 scales, made for use on machine tools, with a resolution of .0005" and a repeatability of .0005", with instant inch to mm conversion and zero reset. And, if you want a display box they offer a 3 axis display box with 3 cables each 6ft long and large red LEDs for display for US$259. They have a single axis with large fromat disply and a 37" scale for $105. WT has a web site at http://wttool.com Someone asked about RPM- no, these calipers will not measure RPM, just the position of the table. ron ginger ------- Date: Tue, 25 Dec 2001 03:40:55 -0000 From: "terry6453" Subject: Re: DRO and calipers Hi All, I got the digital machine scale from Wholesale Tool today. Unlike hand calipers, these things are built really big and tough. Lots of stainless steel and rugged! They are definitely made for hard use. They can be mounted in all kinds of ways. I tried one way but it was too loose. I ended up just using double-sided foam tape to stick it on the side of the headstock. That actually works perfectly fine although that sounds "too" simple :-) I coated the mating surfaces with a thin coat of oil and rubbed it off well so the tape would be easily removable (I didn't want to drill any holes in the mill). I did make a little plastic spacer and a quick (needs improvement :-)) weight for the slide. The 12-inch scale cut down may fit nicer but it costs almost twice as much. I could easily get 0.5 mil repeatability and its readout matches the hand wheels and the other Starrett gages. So it works fine and it is easy and smooth to use. I was having a little trouble getting really accurate Z dimensions before but now it's child's play! There is a picture at: http://hot-streamer.com/temp/Sherline/Pc240007.jpg The instructions list a wide variety of things to do if it stops working including taking it apart and cleaning the switches and such. They thought of all the same things we did ;-) However, I don't think this will be breaking anytime soon. For a nice $50+ digital readout it is prefect and I really like it. I think they are too big for the X and Y table movement. However, I have just been using digital calipers against the metal edges there which works fine. I can also verify that the graduated hand wheel marks are very accurate so using them is no problem either unless you think in absolute dimensions and can't count turns like me ;-)) I also got that fancy turntable today. Definitely worth the $200+. It is solid steel and works perfectly! It will be perfect for wheels, rotors and such :-)) Time now to go play... Cheers, Terry ------- Date: Sun, 6 Jan 2002 00:07:17 -0500 From: "Jeff Bissonnette" Subject: New member/comments on DRO Hello all! I'm a new member to this list as of tonight, though I've known about its existance for some time. I currently own both a Sherline model 4000 lathe and model 5000 mill (both pre-zero adjust handwheel, and the mill has an AC motor), as well as a bunch of Sherline's accessories. I've looked back through the archives and found a lot of informative and interesting posts. I read through several posts regarding DRO's and using digital calipers as a means of measuring axis movement. I have another suggestion that I've used and it works very well for me. For the Y-axis of my mill, I made a bracket out of aluminum that holds a Mitutoyo 2" dial indicator, which is bolted to the column base with the tip of the indicator running on the back surface of the milling table. Before some of the diehard career tool makers and machinists out there balk at this, let me say this. IT WORKS!! Thanks in part to the excellent manufacture of the Sherline mill! On my mill, running the table from one end of the X-axis travel to the other produces NO noticeable change in the indicator reading. Not sure if all other Sherline mills out there are the same, but mine is great... Anyway, it was cheap and easy to make, I purchased a 3/8" reamer just to make such brackets (most dial indicators have a 3/8" stem), which makes it even quicker. Though with my existing 1/4" max. cap. drill chuck I had to use my 3-Jaw lathe chuck to hold the reamer!! Anyway, the Y-axis was easy because 2" of travel is more than enough for what I need to do with it, hence the 2" DTI. For the X-axis, I came up with a similar solution as those suggesting using a digital caliper but I instead substituted Mitutoyo's Bridgeport Z-axis DRO. I used laser cut steel brackets bolted to the mill table to hold the unit, and attached it to the mill saddle via aluminum and steel parts. It too works very well, "great" even though the amount of travel is limited to about 5" while it is installed on the mill. Again, for the small parts I machine that is not a problem... I've found it to be dead accurate, and I can often "hit" dimensions using it to +/-0.0005" if not "dead on". The only problem I have with it is due in part to how I've tied it into the mill saddle. I've made it removeable, which creates about 0.001"-0.002" of "play". Not a serious problem; I just have to remember to use the same "trick" used when counting hand wheels, that is move in the same direction and if you have to reverse direction go farther than you needed to go and come back. If I would screw the bracket on the saddle and mounting bar together, I'm sure that this would eliminate any problems with this "play". In either case (indicator and/or Mitutoyo DRO) I have experienced NO problems with vibration, or either measuring device "failing" under use. I've been using my set-up for about 2 years now in this configuration... For your viewing pleasure I will post photos to the "files" section showing my set-up. I'm glad to be a part of this group and look forward to the plethora of very useful information I will get from you guys. Best Regards, Jeff B -------- Date: Sun, 06 Jan 2002 15:09:17 -0500 From: ron ginger Subject: Re: DRO- Dial Indicator Jeff Bissonnette wrote about using a 2" travel Dial Indicator on his mill. A friend of mine does this, but in a somewhat simpler fashion. He mounted his mill and lathe on a table top covered in sheet metal- a fairly thick sheet, and painted it nicely. He uses a magnetic base indicator stand which he can plop down anywhere around the mill or lathe as needed for a particular setup. Its fast and easy to move and adjust, and those magnets are plenty strong to resist moving. He actually has 2 or 3 indicators on stands so he can use a couple at a time. Also works very well on the back side of the lathe to measure the cross slide travel, or alongside the table for length of turned objects. You can often place them into positions that would never be possible with a fixed bracket, because you drop it down after the setup is made. I cut the case of an old PC apart to use its side pannels for this, they are well painetd and plenty stiff. You do need to be careful that you align the indicator carefully for the direction of travel so you get an accurate measurement, and note dials are only good for about 1% accuracy over the full travel range. But $25 will get a 2" imported indicator form any of the big suppliers, and the bases are always on sale for $10-20. ron ginger ------- Date: Sun, 6 Jan 2002 14:04:38 -0500 From: "Jeff Bissonnette" Subject: Re: Re: DRO- Dial Indicator "A friend of mine does this, but in a somewhat simpler fashion. He mounted his mill and lathe on a table top covered in sheet metal- a fairly thick sheet, and painted it nicely. He uses a magnetic base indicator stand which he can plop down anywhere around the mill or lathe as needed for a particular setup. Its fast and easy to move and adjust, and those magnets are plenty strong to resist moving." Ron, I've done this for my Sherline lathe... Only I use small squares of 1/16" thick sheet steel screwed to my workbench. It works well with the 1" indicators I use so long as you aren't rigorously cranking on any handwheels. I use a small machinist square to align the indicator stem to the cross slide table. Close enough that when you work out the "cosine" error for the few thou it may be off it results in an error of nearly zero for 1-2" of travel of the indicator used. I'll throw a photo in the file folder I created in the "files" section showing my set-up. Most of the time I only use it for Z-axis travel (along the bed). BTW, I went to www.discountcampus.com. GREAT site!!! I found a better solution to the DRO set-up I have. They sell Mitutoyo DRO's and they have longer measuring ranges... I may have to pick one up to retrofit my current set-up!! I'd be able to use the full X-axis range of movement of my machine that way... Jeff ------- From: CaptonZap... Date: Sat Jan 19, 2002 10:26 pm Subject: Re: [atlas_craftsman] Edge finders 1/19/2002, skip_evansx~xxh... writes: << I have two edge finders, one with a straight tip and the other a pointed tip. How is the finder with the pointed tip used? >> After you have prick punched the center of a desired hole, you CAREFULLY put the tip into the punch mark, and center your workpiece. Most Bridgeports and clones have a small amount of down quill feed travel that is spring loaded. The spring doesn't put enough pressure on the point of the center finder to bind it in the hole. With a drill press, you will have to feel your down, and hold a slight amount of pressure while you center the workpiece. A drop of oil would ease your mind. 8) CZ ------- From: Thomas Gilmour Date: Thu Jan 24, 2002 3:11 pm Subject: Re: [sherline] good dial indicator / centering device. Ifbige28673 wrote: > I want a good method for locating the center of round stock for > drilling operations.I was looking at a centering indicator but there > is not going to be enough room for it to fit between the spindle and > milling table.This would in my opinion be the best measuring tool > since it will "sweep" both the ID and OD of round stock and with the > addition of a spindle lock you could square up flat stock along one edge > also.Any ideas or solutions?I have ordered the 6200 DRO outfit from DPP. you're not looking for extremely precise centering you can use a wiggler mounted in the spindle to line up with scribed marks on the part. I've also used my dial test indicator to sweep internal holes and the outer edge of small diameter round stock. Rather tedious but it works, however with the standard indicator point I don't think you could sweep anything larger than .500" or .750". Tom ------- From: "terry6453" Date: Thu Jan 24, 2002 7:43 pm Subject: Re: good dial indicator / centering device. I am not sure what the size of your round stock is but here are three tools that should be of interest. The first is the "edge finder". Sort of hard to explain it but when you see it working you will get the idea right away. It has a 0.2000 inch sliding tip that will slip out of place when it just touches a straight edge: http://hot-streamer.com/temp/Sherline/EdgeFinder.jpg The shaft is 3/8 inch so it fits in the 3/8 inch adapter perfectly. When it "finds" the edge, the centerline is exactly 0.100 inches away. This may be of limited use on round stock since it likes flat edges. Starrett is the usual choice (MSC# 86425246) at a pleasant $17.50. I use it all the time but for flat edges. Probably good to 0.00025 inch. If you have a mark or point you want to drill without any other dimensions to go from, the "Wiggler" is your tool: http://hot-streamer.com/temp/Sherline/Wiggler.jpg You will have to "see" this one in action to get how it works too. You spin it and touch the tip with something and it swivels right to a perfectly placed point. Then its tip will be a perfect point to line up with the mark on the work (magnifying glass). Starrett 828 MSC# 86425295 at $12.40. Almost a must have... Accuracy depends on your eyes 8-) A few mil for me... The tip could be a little shorter, so a friend with a lathe to chop it may be an option. I hear there are other "tricks" for using this tool on round stuff but I don't know them. I think what you really want is the "Last Word 711" gauge by Starrett. Many many uses! It is a fine dial gauge made for touching perpendicular surfaces. It is marked in 0.0005 but you could actually go better: http://hot-streamer.com/temp/Sherline/LastWord.jpg http://hot-streamer.com/temp/Sherline/LastWord2.jpg With this, you can set it to the outer (or inner, it has a switch for both) surface and "play" with the X-Y to get a round piece in perfect alignment (0.00025). You can turn the quill to see how far out of round the work is from the centerline and make adjustments directly. I set it up and tried it and with some tiny practice it is very easy. Cost you more it will!! $:o)) Starrett 711 MSC# 86424314 at $115.00. There are some cheaper types but get the Starrett ;-) It can also be clamped in a vise with an included adapter for other alignment work. It has a 1/8 inch shaft that you can easily stick in a drill chuck or 1/8 collet. The mounting could probably be modified if needed. I use it to align just about everything with the mill and vises. Note that your "round" stock should really be "lathe machined" round. If it is a few thousandths off from round, then you will have to "fiddle with it" :-)) Also, you may need a thin film of oil on the part for these contact gauges to get a "smooth" reading. All three of these are long standing "must haves" of the machining industry and they work very well. Every machinist knows them well and they are just assumed... Aside from gauge blocks (for quickly setting up square stuff, WOW, I use them a LOT!!), you really don't need anything else. Not sure the square blocks will help with round stuff... Cheers, Terry - Gosh! Sometimes I sound like I know what I am doing :-))) ------- From: "Al Lenz" Date: Thu Jan 24, 2002 10:45 pm Subject: RE: [sherline] Re: good dial indicator / centering device. Terry, good info. Here is my Tip of the day: Using double sided tape and a refrigerator magnet, stick a pocket mirror to the mill column. You can see the indicator dial on the backside without getting a crick in your neck! Al Lenz ------- Date: Fri, 25 Jan 2002 22:37:03 -0000 From: "Ted Walls" Subject: Re: good dial indicator / centering device. Are you cross drilling or end drilling? For end drilling I'm not too sure as to what size bar you will be using, but a dodge I have used in the past with end centering round or square bars is to make ,or have made a bar with a 20 degree cone machined in one end the other end say 1/4 for a collet. Mount the bar perpendicular in the vice and, with the vice screws or clamps loose, bring the spindle down so that the end of the bar enters the cone. Tighten the clamps and the bar is now central to the spindle bore ready for drilling. For cross hole drilling, an accurate and easy to make and use tool can be made by machining a piece of round stock about 3/8 in diameter and say 3 or 4 in long to half its diameter for about 1 1/2 in at one end and turned down to suit a collet at the other. Make a 'Y' shaped piece of something like 16SWG material (steel brass or aluminium) with about 1 in long legs with a small hole say 1/16 or 3/32 in the middle of the 'Y' make the same size hole on centre and about 1/4 in. from the end of the bar with the flat on it. Assemble the 'Y' piece to the bar so the 'Y' is upside down and put a good fitting pin thro both the 'Y' and the bar. You now need to "calibrate" the tool by centering a bar below the spindle using the tool. It is easiest to do this with the with the bar along the table West to East so to speak. You can easily see both sides of the too this way. Clamp the bar to the table and bring the tool down so that the 2 legs of the 'Y straddle the bar using a fine felt tip or pencil mark a line central to the bar and onto the top leg of the 'Y'. Now raise the tool clear off of the bar, rotate it thro 180 degrees and lower to straddle the bar again. Note the misalignment of the lines. Move the table half the misalignment and mark the top leg of the 'Y' only. Clear the bar rotate and repeat again. If all has gone well the second line you marked will line up with the line on the bar. If not repeat until it does. When the lines align both ways the tool is "calibrated". Permanently mark the lines with a scriber. From now on all you need to do, to centre a bar, is clamp it to the bed or hold in a vice, put the tool in the spindle, bring it down to straddle the bar and move the bar using the handwheels until the lines on the 'Y' and the bar align. The centre of the spindle is now central to the bar. Once made the speed and ease with which a wide range (size) of bars can be centralised makes the effort of making the tool well worth while. If you can't understand my ramblings contact me off list and I'll send you a couple of simple sketches. ------- Date: Tue, 05 Mar 2002 16:03:53 -0800 From: Ben Bennett Subject: telescoping gages I bought some telescoping gages from HF (made in China) and it drives me nuts trying to use them. Whenever I try to measure an inside diameter with them it always comes up short. The way I do it is, I press the probes together, tighten the handle (for want of a better name), stick it in the hole, loosen the handle (letting the probes pop out against the inside of the hole) and tightening the handle. Then I mike it. What am I doing wrong? Is it me or the gages? Ben Bennett ------- Date: Wed, 06 Mar 2002 11:02:01 -0700 From: "Ron Shaw" Subject: Re:Telescoping gages I have a set of those gages, and they drive me nuts, too. They are better than nothing, but not by much. The anvils stick closed and won't release when you loosen the screw, etc, etc. Take them apart, as I did, and you can see why. There is NO finish work on the parts whatsoever. Even after cleaning up the ragged edges and whatnot and reassembling, they are not a whole lot better. They are made cheap to sell cheap, but as far as being any kind of a precision measuring instrument, forget it. Ron Shaw ------- Date: Tue, 5 Mar 2002 22:24:17 -0600 From: "jerdal" Subject: Re: telescoping gages Way I have heard is put them in, vertical, cock handle up a bit (hush you Brits, that's not what I meant) off straight, tighten just to hold, then one sweep down with the handle past straight, pull out, snug up and measure. Your problem is likely not the gages, if they don't have a friction problem, but rather with the cut. A rough cut is usually a couple tenths of mm (few thous) over what it measures due to the ridges in the bore. The rough bits smash down easily, and bore seems to have expanded. Jerry ------- Date: Wed, 6 Mar 2002 01:07:42 EST From: catboat15x~xxaol.com Subject: Re: telescoping gages In a message dated 3/5/2002, greyhawk200x~xxatt.net writes: > The way I do it is, I press the probes together, tighten the handle > (for want of a better name), stick it in the hole, loosen the handle > (letting the probes pop out against the inside of the hole) Two possible reasons. Are the anvil and spindle of your mike pushing the probes together? Are you sure you are measuring on the full diameter of the hole and not on a chord? How far off are you and is it consistant? Oh, make that three reasons possible defect in gauge when tighting the handle it may shift the probes a bit. Most of our amateur tools require getting a feel for measuring to high precision. That is the reason a mike is better for outside measuring than a dial caliper as a caliper does not have the feel and the measuring jaws deflect differently depending on how hard you close the jaws on the work. John Meacham California High Desert 12 inch Atlas, Minimill, rusty file ------- Date: Wed, 06 Mar 2002 04:23:46 -0000 From: "jdmichael2001" Subject: Re: telescoping gages Ben, the technique I was taught was to insert the gage in the bore at a diagonal, then loosen it so the arms telescope out to the I.D. Snug up the handle, but not too tight, then pivot the gage so the arms are compressed through the smallest effective diameter ONLY ONCE. Withdraw the gage and mike it. Again, pivot the the arms through the mike faces to get the same feel as when you pivoted in the bore. It will help a lot to have a practice bore you know the size of acquire the right feel. It takes a while to learn to trust the once through the bore and to feel the same drag in the mike, but we used to measure to tenths with telescoping gages for shrink fits. Jan ------- Date: Wed, 06 Mar 2002 06:32:10 +0000 From: Jon Elson Subject: Re: telescoping gages > tightening the handle. Then I mike it. What am I doing wrong? Is > it me or the gages? These things are pretty hard to use. When you release the clamp, you have to wiggle the handle gently to allow the spring pressure to force the feeler tips to find the true diameter. On the larger gages, you need to use hand pressure to offset the weight of the gage so that it is at true center. After clamping the tips, I then move the handle to see if the tips are truly on center, of if there is some free play. If there is free play, the tips are not at the true diameter. So, I try again. Some of these gages may not be machined well, and the tips may be drawn in when you tighten the handle. If this is the case, return them, or take them apart and see if some rough egdes on the interior parts are causing the clamp to hang up. There is definitely some acquired feel to using these, and only us cheap home shop machinists use them. The pros use rather fancy direct-reading bore gauges. The REAL pros use Cadillac air gauges, but these are REALLY expensive. For smaller holes, pin or plug gages are relatively cheap, and work VERY well at sizing holes up to 1/2". Jon ------- Date: Tue, 5 Mar 2002 23:38:26 EST From: LADDERBARx~xxaol.com Subject: Re: telescoping gages You must put the gage in over center (Handle tilted up or down) tighten up the handle rotate it over center pull it out and then you have a size. have fun Mike ------- Date: Thu, 07 Mar 2002 14:52:11 -0800 From: Ben Bennett Subject: thanks-re telescoping gages Thanks for all the advice on using my telescoping gages, except for the wise guys that told me to take them apart.... boy! What a lot of little parts & springs. Maybe the best advice was to throw them away. I think I've got a pretty good idea now. Cock it, release it, cock it the other way, pull it out and measure. I think my trouble was I was I was wiggling it around, trying to get it perfect after I set it. Ben Bennett ------- Date: Mon, 11 Mar 2002 16:20:56 -0800 From: "Van Lupo" Subject: Indicating using electrical contact Is it just me or have others figured this out? I bought a "Signal Lite" edge finder the other day that uses electrical contact to detect the edge of a work piece only find out that it wouldn't work on the Sherline machines. Well being an electrical engineer and all, I quickly figured out the problem. It turns out (not too surprising actually) that because the Sherline cross slides are all anodized, there is little chance that electrical current can ever flow between the work piece and the spindle or cutter in the case of the Lathe. That's when the lights went on (pun intended!). So, I thought I would share my excitement (pronounces discovery). Using a simple conductivity meter or light you can connect one lead to the spindle or tool and the other to your work piece and then simply bring the tool into contact with the work piece and when it touches the conductivity indicator will let you know where the surface or edge is. Simply subtract out the proper tool compensation and your good to go. Now my question to the list is, is there really anything wrong with using this technique for determining the edge or surface of the part? I can't seem to see any reason why this couldn't be used in place of a dial or test indicator either. Simply note the hand wheel settings at two different locations and then take the difference to adjust the work position. Anyone have comments on this? Van ------- Date: Tue, 12 Mar 2002 14:10:03 -0000 From: "docholliday01201" Subject: Re: Indicating using electrical contact Have done it for years. I use a multimeter on resistance setting which has beep on full continuity. I use big alligator clips one on work one on the spindle at the top where the drawbar is. Usually the beep tone is all I need, sometimes I have to watch the resistance on the meter for sudden change. The only drawback is that if there is a chip there it will short it out and give an innacurate reading, or if your coolant is conductive. (I use non-conductive ethylene glycol.) The meter is part of the shop tools now !!! ------- Date: Tue, 12 Mar 2002 20:06:52 -0000 From: "flosi2001" Subject: Re: Indicating using electrical contact I use a homebuilt conductivity probe that I made long time ago from plans in a magazine. It is a very simple gadget, that lights a diode when the resistance is less than 10 ohm. I have also tried my multimeters for this, but they don't work as well as they peep at a much higher resistance. Flosi Gudmundsson Iceland ------- Date: Sun, 17 Mar 2002 23:33:15 -0000 From: "gbesch" Subject: Re: Instruments In sherline, "Graham Knight" wrote: > Now that I'm back from holiday and have time to use > my new Sherline lathe, I intend to go and buy > myself some measuring equipment this week Graham, besides a good set of calipers and micrometers, the only instrument I consider a "must have" is a dial indicator. However, it's also nice to have a dial test indicator. Sometimes it's the only way to center a part in the 4-jaw, as when you have a part with an irregular outer surface, but which has a finished center hole. The lever of the dial test indicator can ride against the inside surface of the hole where the dial indicator simply can't reach. Over the last few years I've accumulated a basic set of instruments one-by-one as the need arose for different jobs. I have several dial indicators of various lengths from .5" to 2". I also have a set of 0- 3" outside micrometers, a depth micrometer, three dial calipers (two 6" and one 4"), and a dial bore gauge. I wish there were a good supply of used instruments here! As you've observed, a magnetic base isn't much good on the lathe cross-slide. However, you can get a bit of steel plate to put down in front of the lathe for the magnetic base to stick to. Another option is a shop-made indicator holder for the lathe cross-slide. I made a simple one as follows: Using a 2" length of 2x1" aluminum bar, face off the top and bottom. Put a clearance hole down through the top for a 10-32NF clamp screw, about a half-inch from one side of the 2" width (leaving room for boring a hole for the indicator without running into the clamp screw). Counterbore the bottom of the hole for a Sherline T-nut. Clamp the new indicator tool post to the cross-slide, mount the drill chuck in the headstock, drill and ream a hole for a close fit on the indicator tube (drilling from the headstock insures your hole will be at the lathe center height). Last, cross-drill down from the top of the new tool post into the hole for the indicator tube, thread 10- 32NF for a clamp screw to hold the indicator in the tool post. A nice accessory for your new lathe indicator would be an "indicator bridge". It's just a little makeshift item to assist in centering square, hex, or other irregular shaped parts in the 4-jaw. Get yourself a bit of flat spring metal (banding strap from an old packing crate or skid works well) about a half inch wide by about three inches long. Drill a hole near one end for a 10-32NF clamp screw, then put a right-angle bend about three quarters of an inch from the drilled end. Make sure it's nicely deburred all over, and you may want to lightly radius the top corners (the opposite end from the bend). You can use it as-is, or you may want to make a base for it to make it more convenient to set up. To use it, mount it to the cross-slide so that it's square to the side of the part you're trying to center, then bring your indicator up to bear against the bridge. As you turn your part to center it, the outer edges should just contact the bridge, causing a reading on the indicator. It's more convenient than having to pull the indicator rod away from the part as you turn it and it prevents bent indicator rods. I hope you enjoy your new Sherline! Greg ------- Date: Mon, 18 Mar 2002 01:41:12 -0000 From: "kentfreeman" Subject: Re: Instruments On the Sherline web site there is a picture of someone using the headstock riser block and the riser tool post. The dial indicator was inserted in the 3/8 hole in the riser tool post. ------- Date: Sun, 14 Jul 2002 00:48:21 -0000 From: "neilunreal" Subject: Re: Indicators Dial test indicators and dial indicators both measure the same thing, distance, but they do it in different ways. A dial test indicator measures distance by angular deflection, while a dial indicator measures it by means of a rack or piston. As Forrest pointed out, one of the results is that it's easier to make a dial test indicator which measures larger distances. It also makes each of the two types of indicators appropriat for different types of measurement. For instance, it is easier to use a dial test indicator to align the milling head and any parts to be milled. On the other hand, a dial indicator can be useful for situations where the absolute distance is important at two different points on a part. I find I nearly always use my dial test indicator for milling alignments, while my dial indicator is often handier on the lathe. If I had to have only one or the other, I'd have a dial test indicator, since it can be used in many of the same situations where a dial indicator is used, and in other situations where the use of a dial indicator would be almost impossible. So I compromised -- I bought a really good dial test indicator and a less expensive dial indicator. Neil ------- Date: Sat, 13 Jul 2002 21:20:22 -0400 From: "Marshall Pharoah" Subject: RE: Re: Indicators This is a good summary. I would like to add that because a DTI works by angular deflection, that the readings from it should not be taken as gospel, especially over a distance of more than a few degrees. I believe this is called tangential error, but my math is extremely rusty. The rule of thumb is: Use a dti when testing alignment. Use a dial indicator for measuring distance. Note that when measuring distance with an indicator, you still can introduce errors due to improper alignment (the indicator becomes the hypotenuse of a triangle and may read less than the acual movement. If you walk into a shop around here, you'll see the pro's using Starret Last Word DTI's or Browne & Sharp, Mitutoyo, Fowler, or a couple of other good brands. For travel indicators they use the cheapest they can get. $6.99 specials from the truck sales if they can get them. DTI's are almost always used with the machine off and are at little danger. Travel indicators are often used with the power on, occaisionally even sacrificed (Watched a machinist take a cut right through the top of one once, on purpose, there was no way to remove it without losing the setup). So, generally, you need both in your shop. I have a Browne and Sharpe Bestest DTI, a Brown and Sharpe 1" Travel indicator, a federal .0001 indicator and 4-5 el cheapos travel indicators. Marshall ------- Date: Sat, 17 Aug 2002 23:39:30 -0000 From: "variousgroups" Subject: finding center of small hole What is the best way to find the center of a small hole, say under 1/4", in a flat piece, not thick, that is being brought to the machine for the first time? The hole was bored somewhere else. You want to lower an end mill of a lesser diameter into the hole and create a key hole-type result. If you place a lesser diameter drill rod in the chuck and measure side to side in X and Y, how do you really know when you've made contact at the sides, or that you're on a diameter? Successive approximations sounds fairly time comsuming and inexact. You could measure electrical continuity easily enough for contact, but what if the piece is Delrin? Does one just have to gauge it by a "tips of the fingers feel" on the lead screws? Any thoughts? Mike ------- Date: Sat, 17 Aug 2002 20:15:33 -0400 From: "Daniel Munoz" Subject: RE: finding center of small hole Here's my quick & dirty method (from a beginner that blindly think he'll become a machinist some day) I use a Sherline lathe dead center, stuck it in the motor taper shaft, and while slowly setting the Z-axis down I manage to center it on the hole until the dead center is low enough to fill the hole completely. Then I clamp the piece, the vise, the rotary table or whatever hold the piece to machine, and voila, I have centered the hole around the dead center's cone. Hum, not the most accurate solution I'm sure, but it was enough for many of the things I needed to do for now. Daniel http://www.nutsnbits.com ------- Date: Sat, 17 Aug 2002 22:03:43 -0400 From: "Van Lupo" Subject: RE: finding center of small hole You use a hole center finder device that you mount in your end mill holder and then spin a low RPM. When it makes contact with the side it will true up until it then kicks out to the side. Record the hand wheel value and then go find the other side and record that hand wheel setting. Subtract one from the other and then divide and you have the center. Repeat for both axis until they match. Takes about three to four passes. That's how I've been doing it anyway. Would love to hear how others solve this common need. Van ------- Date: Sun, 18 Aug 2002 03:50:34 -0000 From: "variousgroups" Subject: Re: finding center of small hole Van--Is the "hole center finder device" that you use the same as an edge finder? Using a dead center sounds okay, in that a cone held in a chuck or in an end-mill holder ought to "find" the center of the hole, but irregularities in the hole's outer rim will invite imprecision. Perhaps one solution is just to run a fine, flat sharpening stone lightly over the surface around the hole first. Clamping will introduce some imprecision, too. But then again, this is a hobby-type tool. Mike ------- Date: Sun, 18 Aug 2002 00:17:08 -0400 From: "Van Lupo" Subject: RE: Re: finding center of small hole Mike, a hole center finder is very close to the same as an edge finder except that the end is a pointed cone rather then a straight. Beyond that the device works the same way as an edge finder. Van ------- Date: Sat, 17 Aug 2002 21:36:44 -0700 From: "Marcus & Eva" Subject: Re: finding center of small hole The best and most accurate way is with a dial test indicator. My Mitutoyo has a 0.030" tip so I can indicate a 0.050" hole directly. Anything smaller, I push in a gage pin of the right diameter and then indicate the pin. Cheers Marcus ------- Date: Sun, 18 Aug 2002 07:51:12 -0500 From: "Nance, Tom" Subject: RE: finding center of small hole Hi Van, That sounds like a very elegant way to find the center of a hole but I see a major problem. To move from one side of the hole to the other you must, of course, change direction of the table movement. When you do that, you introduce backlash into the scheme and you won't get a true reading from your handwheels. Sorry, but that's one of the vagaries of driving a mill. The only way I have found to find the center of a hole on the mill is to mount a Dial Test Indicator in the mill spindle and indicate the inside of the hole as someone else mentioned earlier. It's a real pain in the neck - and I mean that quite literally because the dial moves around and so YOU have to move around with it to see what it's reading around on the back side. Doing it that way is tremendously accurate and once you've done it a few times, you can center the mill fairly quickly. Tom Nance ------- Date: Sun, 18 Aug 2002 06:30:58 -0700 From: "Dave Hylands" Subject: RE: finding center of small hole If you have one of the edge finders that shoots to the side when you hit the edge and comes back when you back away (they have a spring in them), then you can eliminate the backlash problem. This of course, only works for holes larger than the edge finder, typically 0.2". You find one side the traditional way, moving the table until you just see the edge finder move. To find the other side, you move the table until you just see the edge finder move, and then to get rid of backlash, reverse direction until the edge finder has just gone back to center. You've now found both edges in one axis. Center that axis. Since you've eliminated the backlash, if you overshoot center, you need to overshoot in the other direction and come back from the side where you obtained the 2nd measurement. Repeat for the other axis. ------- Date: Sun, 18 Aug 2002 10:06:37 -0400 From: "Van Lupo" Subject: RE: finding center of small hole This is correct, but I might add that to do this accurately you must feed the hand wheel until the edge finder starts to spin true and then just a little more and the edge find then kicks off to one side. It is at this very point that the find kicks off to the side that you want to read your hand wheel setting. As Dave mentioned you must always subtract your previously measured backlash from the hand wheel readings each time you change direction. This is true for any measurements you make using the hand wheels. I might also mention that it is very important to make certain the hole is clean around the edge your taking your measurements from. Any burrs will obviously drastically affect your outcome. As mentioned in previous post, a dial indicator is much more accurate but also requires considerably more setup effort and time. Also is generally better used on larger holes I think. Van ------- Date: Sun, 18 Aug 2002 10:14:39 -0400 From: "Dan Statman" Subject: Re: finding center of small hole > That sounds like a very elegant way to find the center of a hole but I > see a major problem. To move from one side of the hole to the other you > must, of course, change direction of the table movement. When you do > that,you introduce backlash into the scheme and you won't get a true > reading from your handwheels. Sorry, but that's one of the vagaries > of driving a mill. Do you not have an indicator set up to measure the actual table movement? Or do you solely rely on your handwheels? With a plunger type indicator you can easily measure the actual table movement and then abcklash is NEVER an issue for this. This is also what is needed to measure the value of the backlash. Daniel J. Statman, Statman Designs www.statmandesigns.com ------- Date: Sun, 18 Aug 2002 07:32:15 -0700 From: "Marcus & Eva" Subject: Re: finding center of small hole Hi Tom and others: Best way around the neck bending problem is to bum a small mouth mirror off your friendly neighbourhood dentist. They are only around 6 bucks orso, and dentists toss the scratched ones all the time. Going back to all the interesting responses we've had on this thread, the only good way to pick up a hole is with a dial test indicator. This is what everybody in the trades uses and with good reason. Edge finders are useless for small holes, and cone centers are hopelessly inaccurate. Edge finders are not terribly accurate either; even for finding edges. Many harder grades of steel will magnetize a bit when they are machined, and will yank an edge finder into the kickout position prematurely. They are therefore useless on steel!!! The best way to find the center position of a rectangular block to within tenths is to chuck a dowel pin into the collet and feel the gap with a feeler gage or a Jo block. If you spin the dowel by hand so you're always presenting the same point to the successive sides of the block, you can accommodate any runout in the collet and dowel. This is the fastest and most accurate method I have ever found to pick up a block center, and I have tried them all over the years. I've seen lots of toolmakers farting about with Dial indicators and edge finders and depth mikes. They all still routinely screw up the positions of their work by 0.001 to 0.002". I can feel a movement of 0.0001" easily on the CNC or a tenths DRO equipped mill, with a feeler gage if I'm gaging whether the feeler will slip into the gap between block and dowel or not. For accurate location of a single edge, I use a similar method: I stick a Dial onto the dowel and spin it by hand. I set the clock so the runout reads identically on either side of zero, and then mark the zero positions on the dowel with felt pen. I mike the dowel across the zero positions and then feeler gage my way up to the edge with the dowel positioned to present the marked point tangent to the edge. Add up the feeler thickness plus half the dowel diameter, and set your offset. You will be within 0.0005" of the correct location without breaking a sweat. So toss your edge finders into the trash where they belong, and go score yourself a couple of hardened dowel pins. Your workpieces will thank you. That's my Sunday morning rant, and I'm stickin' to it!!! Cheers Marcus ------- Date: Sun, 18 Aug 2002 11:08:02 -0400 From: "Van Lupo" Subject: RE: finding center of small hole Sometime ago I posted another technique that I have been using with reasonable success. This involves a little electrics effort but is simple enough to put together. I simply use continuity tester and measure for continuity between my work piece and the machine tool. Of course this only works with metal materials it has been quite reliable. Only issue is finding the highest pint on the tool to make the contact with. Clip one lead to the tool or head stock and the other to the stock or hold down and you're ready to go. It turns out that with the anodizing used on the saddle and cross slides there is no continuity between the head stock or tool and the cross slide or stock mounted to it. Is anyone else using this concept? Van ------- Date: Sun, 18 Aug 2002 15:25:18 -0000 From: "variousgroups" Subject: Small Hole Concensus: dial indictate yes wiggler no The feeler guage method Marcus describes, which involves a dowel of known diameter, relies on known quantities and assumes their accuracy: the feeler gauge thickness and the dowel diameter. If these come from Starrett or Brown & Sharpe they ought to be as described. There is also some need to rely on a well-developed, probably over many years, tip-of-the-fingers feel to use Marcus's method correctly. Anyway, the consensus seems to be that indicating the hole gives very good results and is widely used. The only "center finder" tools I can find in MSC are the "wiggler" sets. The consensus seems to be that these are basically not worth their cost, at least in this small-hole context. Do they have any genuine uses? Maybe for larger holes? Mike ------- Date: Sun, 18 Aug 2002 11:57:26 -0700 From: "Yasmiin" Subject: RE: Small Hole Concensus: dial indictate yes wiggler no A wiggle has some definite uses and I for one couldn't do without one. Its not a center finder for an existing hole. However, it is the tool of choice when placing a drill on center on a piece of work that has been carefully laid out. With a wiggler you can place the drill over the cross mark for the center of a hole that is being drilled. The only more accurate method is the use of a centering scope. Of course, you can position all holes relative to one hole but that's a lot of work that isn't necessary in most cases. If you have a DRO then relative position is simple but older methods take some care to do well. Regards, Yasmiin ------- Date: Mon, 19 Aug 2002 19:30:13 -0700 From: "Marcus & Eva" Subject: Re: :getting holes in the right spot Hi Mike and others: Actually, the feeler gage method does not require any special feel to it. It is amazing the first time you experience it, but a movement of 0.0001" is easy to discriminate. A feeler gage that is just nipped so it drags will fall out by itself if a 0.0001" movement is made away from the part, and will be pinched too tightly to pull out easily if a move of 0.0001" is made toward the part. The best way to use this method quickly, is to advance the pin toward the edge until it is obviously too close to slide in the feeler. Push the feeler into the gap as far as you can and start moving the pin away from the part. Keep pushing on the feeler and keep moving the pin away until the feeler slips into the gap easily. Now lock the slide and take up the backlash in the leadscrew. Unlock the slide again and advance forward slowly while wiggling the feeler. When it just starts to drag, you are there. Since you measured the pin and the feeler, you don't need to care what size they are; any old smooth round pin will do. When I'm too lazy to pull the cutter from the collet, I just use its shank as a pin. If I don't have enough of the shank sticking out for a proper feeler, I use a bit of wire. When you're centering a block you don't need to account for runout either, because you always place the same point on the circumference of the pin against the surfaces that you are gaging from. Yasmiin: you commented on the usefulness of a wiggler. I find them occasionally very useful too. Here's an old toolmaker's trick that provides the best wiggler I've ever found. Take a lump of Plasticene and stick it on the end of whatever tool you happen to have in your spindle. Stick a small sewing needle or a straight pin into the plasticene so the point is roughly centered on the long axis of the spindle. Turn on the machine at about 1000 RPM or so. Hold a bit of any old thing (like your fingernail) against the side of the pin until the point runs dead nuts true. Now pick up your scribelines with a good spyglass and the point. You don't have to change tools, and you can set it up over and over in seconds. It's also dirt cheap and when the point gets dull, just toss it and raid the family sewing basket for another one. By the way, there is a bad habit that I've seen even "experts" writing "how to" articles in Home Shop Machinist and other magazines doing all the time. Almost everyone centerpunches the intersections of holes they intend to drill; even when they are drilling on the mill. Don't do it... it sets you back if you intend to put the holes in accurate locations. No one can freehand punch perfectly every time, and the punchmarks that are off position just obscure the intersection of the scribelines and pull the drillpoint into the wrong spot. It's a perfectly valid way to position rough holes on the drillpress where the part can flop around and center itself on the punchmark, but it's worse than useless on the mill. A far better way if you are positioning holes IN THE MILL that are not too critical, is to scribe your lines, and then pick up each line independently by just touching the point of a spinning centerdrill to the job and seeing where the dimple is in relation to the line. Once you've centered on the first line, zero your first axis. Now deliberately move off your first line a bit (say 0.050" or so) and pick up the other line the same way. Once you've picked up the second line to your satisfaction, you can just reposition to zero on the first axis and you are there. The secret to success with this method is to keep the dimples tiny, and to make a new dimple in a new spot every time you shift an axis around while you're trying to center it. Make them close enough to the intersection