recutting on lathe

[MBG]

Okay does anybody else experience with their HASS lathe (sl-30) that after a turning operation is completed and you rerun the operation that it takes an additional material off.

Is this common or not?

[Geof]

How much additional material?

Are you doing a finish cut with a finishing tool taking off just a very small amount?

Are your tools sharp?

You will always get a little bit of deflection either on the part of the workpiece or on the machine so if you just do a cut something like 0.1" deep and then go back over it you will always take a little more off.

Even when you do a final cut with a nice sharp tool sometimes when you go back you will find little wisps of material taken off. The machine specs say that it repeats to within +/-0.0002" on the X axis measured on the diameter I think. Theoretically it is possible that recutting could take off 0.0004" on the diameter and the machine is still behaving within specs.

[MBG]

Same tool and it will take off material even AFTER the 2nd cut. It will take material off on the 3rd and the 4th cuts.

[MikeOD]

Every lathe I've ever used in my life does this...I've lost count of how many cuts it will continue to make really really tiny chips. It has a LOT to do with what type of edge the tool has, what type of projection length you see on the tool as well as on the part, how much material you cut on the finish path with the finish tool...material of the work...lots of variables, surface pressure differences and whatnot...however that said, once you have a normal roughing and finishing operation programmed, and you have the tool offsets dialed in properly (adjust the calibration of the tool pre-setter if you have one and you find you're always adjusting the offset when you just set a fresh tool on it), along with the proper stock allowance for the finish tool...I'm betting you'll be very impressed with how repeatable the machine is...properly use the tool wear offset as the machine runs, and remember to wipe the wear offset out when you rotate or replace an insert and I don't think you'll have a problem.