3 jaw chuck run out after machining

Hi,

I'm in the process of commissioning my lathe, when I place a dti on a machined length of bright bar which has been turned in a 3 jaw, I get around 0.02mm run out on the machined surface. Does this sound acceptable?

Edited By Matthew Davenhill on 30/05/2017 19:38:30

Going by a recent thread on here you have quite a reasonable 3-jaw. They are never going to be spot on

Not sure what you are saying Matthew. Are you measuring the runout on the bar you have just skimmed? Without having removed it from the 3-jaw? If so, it wouldn't tell you a great deal. If not, then exactly how are you measuring it?

20 micron runout would be pretty reasonable....

Murray

Good point, if one is measuring a bar in situ after it has been machined I'd expect it to be a darn sight better than 0.02mm runout.

However, if the runout of the chuck is 0.02mm on an inserted bar (no machining) that's pretty good.

Andrew

This is the reading on the freshly machines surface, any thoughts on the cause? The mounting surfaces are clean.

What is the diameter of the bar and how far away from the chuck are you machining? What depth of cut and feed are you using? What type of tool are you using HSS or insert tooling?

Mike

Tipped tool ,about 3 thou cut an inch from the chuck

Are you saying that the lathe is producing work which is circular that is not central to the axis it has been turned on?

What is the 'profile' of the DTI reading as the job is turned through one revolution? (could be three lobed for example)

How good is the surface finish, also in relation to the diameter of the DTI probe radius, Are you just seeing random variations in readings as the tips goes over the hills and dales?

If the turned part is truly circular but off centre then I'm baffled.

Ian P

Slack headstock bearings.

A 3 thou cut is likely to be rubbing/pushing the insert tool off the work, try again with a fresh insert and a heavier cut on a bar of say 1" dia that won't flex.

I thought you were reversing the work in teh chuck in my earler comment.

If you want to take off .003", I think you would be better off with HSS.

Ian S C