Thread: Lathe chuck forcing work piece out???

There seems to be a little confusion here- seems to me the OP is turning toward the chuck whereas a few replies seem to assume he is turning away from the chuck?

I would suggest that the part is walking out of the chuck under the lateral pressure of the relatively heavy cut, muck like a long part supported in a fixed steady will walk out of the chuck if the steady is not properly aligned. Perhaps your old 3-jaw chuck is not able to provide a good enough grip for heavy cuts.

Originally Posted by Pete O

There seems to be a little confusion here- seems to me the OP is turning toward the chuck whereas a few replies seem to assume he is turning away from the chuck?

I would suggest that the part is walking out of the chuck under the lateral pressure of the relatively heavy cut, muck like a long part supported in a fixed steady will walk out of the chuck if the steady is not properly aligned. Perhaps your old 3-jaw chuck is not able to provide a good enough grip for heavy cuts.

Correct, my deep cuts were TOWARD the chuck. I try to only do light cuts in the other direction, to be kind to the spindle lock nut+clamp.

The chuck is a 4" Pratt, but has had a bad life serving school students.

I have been tempted to buy another one – maybe a 6jaw?
...but now a larger lathe has appeared, no need once its brake is repaired.

I agree with oxx/steve, the chuck jaws are bellmouthed.
Lighty tighten à length of stock and push and pull the end of it and you see that the outer ends of the jaws are not gripping

Hi Guys,

Probably not applicable here, but I've seen carbide insert holders that have been rubbed on the front face because the tool has been set slightly high.

One thing that did surprise me a little was to discover that the jaws on my four jaw chuck are tapered towards the back. If they all had the same taper I wouldn't have been as surprised, but they all vary. Pictures in my "Brooks Grinder" thread in projects.