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Thread: Lathe bed wear
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14th Sep 2012, 05:51 PM #1
Lathe bed wear
Hi
This pic is from the Hendey factory pics series. I am wondering if this is a legitimate method of checking older worn lathe beds for a definite amount of wear . This method pictured is of a new machine being checked out .
. alignment.jpg
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14th Sep 2012, 06:07 PM #2Diamond Member
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That's an interesting question. It must be accurate on a new machine - gives a good base/allowable reading (for the factory to pass it out). But you'd have to watch out for dents/dings etc on the bed of a older lathe.
Ben
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15th Sep 2012, 09:59 AM #3Distracted Member
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I'm not really understanding that. But I have to assume Hendey knew more about making lathes than I ever will. Maybe one of our experts can help?
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15th Sep 2012, 12:17 PM #4Most Valued Member
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He is checking for parallel between the carriage and the tailstock ways right? Though he appears to be measuring on the flat on the top of the way. Which I guess would be ok to do at factory if you knew they were ground at the same time as the sides. No good once the machine has been used though.
On second thoughts, if one assumes those two surfaces were parallel when it left the factory, as the top of the way gets little to no wear.... maybe you could use it as a test as any out of parallel would be wear in the carriage ways?
Now where did those experts get to?
Stuart
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15th Sep 2012, 12:47 PM #5
Its a problem in checking way allignment that the individual ways wear at different rates. Finding a reference surface from which to survey is the key to the problem. Often a lathe maker will grind a flat way that is recessed from the main ways, and hence left untouched by wear. I have seen lathes with the underside of the back way ground for use as a future reference.
GregIt's all part of the service here at The House of Pain™
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15th Sep 2012, 11:12 PM #6Cba
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The guy has mounted the indicator on the saddle, and is measuring the front tailstock way whilst moving the saddle. I think this would be a legitimate method, even on a worn lathe. It is fair to assume that the headstock ways are not much worn close to the headstock, while the main ways would indeed be worn mainly close to the headstock. It may not tell you though, if the front and rear bedway have different wear. That you could better check by measuring a test bar between centers, both horizontally and vertically (of course, you would have to level the lathe first, or else you may confuse bed twist with wear).
I am not sure, what exactly you want to do with the measures so aquired. I would be much more interested in the question, what sort of error does bed wear cause to my workpieces. That you check by cutting a long workpiece and measuring diameter along its length. Bed twist causes a linear error (taper), wear causes a non linear error (horglass shape) mostly close to the headstock. In practical use, bed wear is more a nuisance as you cannot adjust saddle to bed clearance anymore, it is sloppy towards the eadstock and binds towards the tailstock. Bed wear usually goes hand-in-hand with cross slide dovetail wear, the gib strip cannot be properly adjusted anymore, and the lathe may face convex instead of slightly concave.
Chris