Collets

[woodchucker]

Because you say draw 'tube' I presume the tube is hollow and not a solid drawbar? If used with a hollow tube closer, then these likely not MT3 collects but 3C collets. My understanding is that these were standard on the South Bend 9 lathes.

As John said you have a 3c collet, I have a 194?? 9a, it's a 3C.

 

[woodchucker]

OK, so I can look at 3c collets.

Question, how far off the nominal size can 3c collets hold? I notice the free dimension for the SB 3 collets that I have measures +.010 over the nominal dimension. The part I just turned in the 1/4" collet measured .240 diameter, which is -.010 of course. Held fine through most of the process, but chattered like crazy when I tried to part it off. I cut it with a hacksaw then faced it instead.

Any and all information is appreciated.

-Ed

Well it might have been the collet, you may only have had a bite on it and the very end, rather than along the area that is made to hold parts.. not sure how much. So yes, it could have chattered from that.
It also could have chattered from too much stick out on the parting tool, from loose gib screws, from not being perpendicular, to being too low with the tool. You want to be dead center when parting. You can put a scale in between the parting tip and the piece and if it is straight up and down you are probably dead center, too high and it leans back, too low and it leans toward you.
if you part to high it will stop cutting, too low and first chatter, then it can actually lift the part and crash.

 

[ebolton]

I had issues with parting at first, but it hasn't been an issue for me lately, till I tried this part in the collet. I know of the alignment/adjustment requirements, minimal tool stickout, copious oil, etc. I also know the work has to be maximally supported, and that's where I think the problem was this time. It was chattering badly and cutting only minimally, so I stopped before anything broke and grabbed the hacksaw. Turning and facing went fine.

I like the collets for being able to take the part out and returning it without runout, and for not marring the part. Beats soft jaws on a chuck by a mile and a half.

-Ed