Haas Lathe - Tailstock Pressure question

Hi -

We have a Haas Lathe - SL 20 I belive is the model, with a tailstock. Lately we have been getting chatter on the bars we run where we hold one end in the chuView attachment haas lathe pm post question.pdfck and the other end has the center in it. The pressure on the chuck is set at 400 psi, and the tailstock is set at 50. If they push that tailstock harder it starts pushing the part back in the collet. We have a serrated collet on the chuck that we bought a few months ago and still looks to be in good shape.

With all that, my boss said the chuck was supposed to have .159 range and only currently has .110.

We are running proven programs that we just ran about 6 months ago, and are having to back down speeds and feeds to get acceptable finishes.

I am wondering if there is an issue with the chuck, but don't know enough to say that that is most likely the issue.

Does all this seem normal to other people with the same setup, or does it seem as if we may have some sort of mechanical machine issue?

Thanks,
Brian

I attached a .pdf (hopefully, can't tell for sure yet if I attached it correctly), showing the part with a couple reference dimensions, so you can get more of an idea what we are doing with the machine.

View attachment haas lathe pm post question.pdf

A couple of things to check that I've run into over the years, although not specific to Haas:

Where in the chuck's stroke range are you clamping the stock? Clamping too close to either end of the chuck's travel seems to not give very good clamping pressure. This could be related to stock size vs. previous runs. New matl supplier?

Different matl than previous? Different supplier? I've had repeat jobs run terrible with proven programs simply because a different supplier was used.

Last thing I can think of is, are you just holding a blank between centers, or is it a whole bar going thru the spindle? If its a whole bar and its not supported with a spindle liner, I have seen bars walk back into the chuck without even taking a cut.

Booze Daily said:

A couple of things to check that I've run into over the years, although not specific to Haas:

Where in the chuck's stroke range are you clamping the stock? Clamping too close to either end of the chuck's travel seems to not give very good clamping pressure. This could be related to stock size vs. previous runs. New matl supplier?

Different matl than previous? Different supplier? I've had repeat jobs run terrible with proven programs simply because a different supplier was used.

Last thing I can think of is, are you just holding a blank between centers, or is it a whole bar going thru the spindle? If its a whole bar and its not supported with a spindle liner, I have seen bars walk back into the chuck without even taking a cut.

Click to expand...

Booze Daily hit the nail on the head with wanting to clamp mid stroke on chuck.
Also long rods walking out if not supported in the rear.

Harder, smoother material can also give some issue.

When was the last time Chuck was serviced...AKA- taken apart, cleaned and fresh greased. Amazing how little fines can get in there and bind up the chuck. You think your clamping work...but your really just overcoming the internal gunk packed in there.

Have enough hydraulic fluid?
Is the hydro fluid filter clean? I have to change mine every few months or I start to notice it takes too long to open of close...pressure doesn't develop.

Last but not least...could turn end or add a notch to be used as a stop for chuck jaws.