Yesterday I was hardcutting stainless on the new lathe, holding extreme tolerances. What I ended up with was the diameters were insanely perfect, thru 45 pieces (3hrs), the lathe held +-.0001 on a diameter no problem. But the Z wasn't so good. It was strange, the spread from shoulder to shoulder was changing. An example is a shoulder 1.5" from the front. It floated +-.0002. That's strange because the front shoulder repeated on location to within a tenth all day. Same conditions on all the shoulders, taking approx .005/side off. No insert wear whatsoever, im using coated cbn inserts and these things do not wear ever. Everything is real rigid.
Now, my question is are lathe's more accurate in X due to maybe the spindle bearings? The Z axis is pushing on the bearings strait in? Is what I'm getting normal?
Variable: Our lathe chuck is fuxored up, samsung is coming out today. With a gage pin clamped in previously bored steel jaws, boring .3 deep, the gage pin in the chuck all the way to the cut so it's almost clamped on the whole length of the jaws. 250 whatever clamping pressure. I bore and without unclamping it I get .0002-.0003 tir. That should be zero, I never unclamped the chuck? Plus it bounced my indicator a tenth or two. Then unclamp and clamp on that gage pin again and it goes anywhere from .0007 - .002 tir, and each jaw is different. So, maybe this crappy chuck is effecting my accuracy in Z????
Any advice on this matter would be appreciated.