Atlas Is Tapering?

Yes that is write you shim the leg at the tailstock end closest to you, trial and error, put in a little, take a test cut etc. Make sure it is bolted down to the bench this very important.
 
If you can, try turning the same part with a centre in the tailstock supporting the outer end of the part..Could just be deflection at the outer end. If the taper reduces or disappears, what you are seeing is the amount of play in the bearings, amplified by the length of the part. I am NOT saying the bearings need replacement!!!, just maybe reset the preload if they are ball/roller type, or remove shims if they are bronze/babbit plain bearings.
 
so I'm thinking my th42 spent most of its life sitting around.

I took the longest "precision" straight edge I have (6" machinist square) and ran it up and down the ways where the carriage makes its marks. Can't see any light gap and can't even get a .002 feeler gauge to even bite.

Measured the thickness on the same part where the carriage runs with it's gibs underneath and got an even .375 the length of the bed. Well truthfully, I had the carriage all the way back to the tail stock so I didn't measure the way thickness there, but the portion of the bed in question (from headstock to ~14" out) has no variance from the .375 thickness.

I even measured the width of the ways. Consistent 1.499 measurement for both front and rear bed way.

Have yet to check the spindle bearings for play but beginning to look like a possible taper culprit...
 
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If the spindle bearings are good less than a .001 lift than than the bed is sprung a little. The first thing to do if you haven't yet is level the bed and make sure it is bolted down to a solid thick surface. Also turn a piece with a large dia. at least 1 1/2" and use a final cit of only .001-.002. If you still have taper start shimming the leg at the tailstock end nearest the operator. Ps you need a precision level .
 
great white said:
OK. If so, how do I "work around it"?
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You have not mentioned any tolerance either specified by the customer or for yourself if a hobby part.
Ask yourself these questions.

Is the part suitable for use?
If so have at it.
If not then you will have to correct whatever is causing said taper, the choices being hand work (finish it to size with abrasive cloth), fixing the machine or buying a more robust and accurate machine.

Is my quest for tenth's accuracy important?
If so buy a cylindrical grinder and stop screwing around with a lathe for anything but roughing.

I personally have the advantage of mostly using CNC lathes where I can program the taper out of the parts often +- 1 or .002" , you probably do not have this option. On occasion I do small bores for one customer, .6250 +.0004 -0.0000 as shown on the drawing, they are incapable of measuring such a feature and none have ever been rejected and were "suitable for use"
Above all if the product is suitable for use do not worry about a bit of taper.
 
Wreck if you read his original post he clearly says the parts are usable lol
Been hangin out with FOMOGO or what bra? Haha
But true to what he says, working within a thou is actually quite good considering the non precision machine you own, I think the atlas lathes are good hobby machines, mine has served me ok, it lacks but it does most of the jobs I need it too. BTW I have half inch ways, Mic each ways width, I'm not sure what they are but I think they are around inch and a half maybe? But that wear could be causing the taper, not the thickness of 3 8ths
 
chevydyl said:
Wreck if you read his original post he clearly says the parts are usable lol
Been hangin out with FOMOGO or what bra? Haha
But true to what he says, working within a thou is actually quite good considering the non precision machine you own, I think the atlas lathes are good hobby machines, mine has served me ok, it lacks but it does most of the jobs I need it too. BTW I have half inch ways, Mic each ways width, I'm not sure what they are but I think they are around inch and a half maybe? But that wear could be causing the taper, not the thickness of 3 8ths
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I did read the entire post and was merely pointing out that chasing tenth's on such a machine will be maddening at best.
 
I totally agree wreck, and personally I think a thou tolerance on that machine is exceptional, given its stock used condition.
Scraped and fitted it may be able to be called high precision...
 
chevydyl said:
BTW I have half inch ways, Mic each ways width, I'm not sure what they are but I think they are around inch and a half maybe? But that wear could be causing the taper, not the thickness of 3 8ths
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I'm glad somebody else is thinking along these lines. I don't have experience with anything but a flat-way machine, but it just seems to me that it would open some potential not typically encountered with Vee-ways. Or at least that's what I think. The edges of the ways wear, and after a while a very slight "waist" develops in the highest traffic spot. Gibs are no longer as snug as they were outside the waist, and the carriage can slew just a bit more in that spot than before. I'm thinking fee-way machines must hold that potential at bay more effectively, but like I said, just my thinkin'

-frank
 
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