Watchmakers lathe accuracy

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

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henryr
Posts: 25
Joined: Mon Jan 15, 2018 1:20 pm
Location: Connecticut USA

Watchmakers lathe accuracy

Post by henryr »

This may be hard to believe but the Boley Leinen 8mm lathe, I've owned for 15 years has amazing, to me, spindle runout accuracy.
About 5 five years ago I measured the spindle runout, starting with a last word indicator with .001 divisions and the indicator never moved. I switched to a .0005 division dial indicator and again no movement. So I switched to a .0001 division indicator and saw very slight hard to see movement.
Since then I’ve acquired a Mahr Klein Millimess 9129 and last night I went through the .001 to .0001 indicators again and got the same results. So I set up the Mahr indicator and the pointer moved about 1um which is equal to .00004 (1um actual vale is .00003937…..). This is amazing to me or is it normal for watchmakers lathes? All my indicators are calibrated using my Mitutoyo height master.
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Harold_V
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Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Watchmakers lathe accuracy

Post by Harold_V »

I've owned a Starrett Last Word thou indicator since 1958. It has been returned to the maker once, many years ago, because it wasn't reading properly. To expect it to display a reading when there is little movement is not reasonable. I have since purchased, and now use, (3) Brown & Sharpe BesTest .0005" indicators, which I find to be bullet proof. The only use I can find for the Last Word, now, is in taking taper out of of a grinder. I used to use it regularly when I operated a centerless, for that purpose. It was up to the task.

I'm not the least bit surprised by the minimal reading you've determined on your watchmaker's lathe. The harsh reality is that as parts get smaller and smaller, tolerance, too, must shrink. I would expect a high level of precision in the spindle, to assure pieces being round. A couple tenths on a ten thou diameter is a large percentage in the scheme of things.

You certainly have some fine instruments.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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GlennW
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Location: Florida

Re: Watchmakers lathe accuracy

Post by GlennW »

You may be exhibiting some significant cosine error in that first image.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
pete
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Joined: Tue Feb 10, 2009 6:04 am

Re: Watchmakers lathe accuracy

Post by pete »

I have the same Millimess indicator that was built by Mahr for Mitutoyo and there's a small tag on it's back saying so. Probably the only difference between mine and yours is the gauge front on mine has the Mit logo on it and mine is marked in imperial divisions. There one of the better mechanical indicators I know of today. But using a plunge style indicator because the vertical movement is being transmitted through an angle when the indicator is tilted like that will throw the accuracy of the readings way off. The accuracy of the measurements will be reduced by a very large amount so there meaningless. Scroll down about half way to where it says Tilted Indicator for an explanation. https://ludeca.com/blog/alignment/2308/ ... alignment/ But there's lot of other sources for how that tilt affects the readings.Plunge type indicator stems have to be as square and at 90 degrees as closely as possible to the surface being checked for any measurement to be accurate. Doubtful it would be a direct fit, but you'd need an attachment much like this, https://www.starrett.com/metrology/product-detail/670B to transfer the horizontal rise and fall internal for run out checks on the spindle surface to a vertical movement an indicator of that type can measure.

Edit, Glenn is a lot more concise and faster at typing. :mrgreen:

There were a lot of watch making lathes and some even larger one's made using extremely hard high precision ground and in some cases lapped spindles that used tapered bearing journals that matched softer ground and lapped cast iron tapered sleeve bearings. My guess is the the better manufacturer's like your Boley assembled the head stocks and then ground the spindle bores and tapers while they were being spun in there own bearings. It's still one of the best and most accurate bearing designs available and the lubrication clearances can be set very accurately. But that accuracy can also be quickly destroyed just from lack of lubrication. If that's what you do have, then probably it has some pretty specific oil type requirements. Substituting a different oil and especially weight would not be a good idea. If you do know the oil brand and exact type the OEM specified and it's no longer available, any larger oil manufacturer can recommend something that's current that will work just as well. If you don't already know of them? Boley also made extremely accurate jig boring capable mills, http://www.lathes.co.uk/boley-miller/ and to lesser accuracy, a few more standard horizontal and vertical mills.
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