Collets

ebolton

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Feb 8, 2017
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I could use a primer on collets. I inherited my 1966 9A lathe, and it came with the handwheel draw tube, 3 identical collet closers, and 14 collets from 1/16 to 7/16 including a 1/4" square collet. Some of the collets appear to be original South Bend parts, and are marked with the number 3 along with the size. Some are just marked 3 along with the size, and I guess they are 3rd party. Some aren't marked at all, and appear to be custom diameters for some job the original user must have needed.

I just turned a knob for my motorcycle using one of the collets, and it worked out well.

I was wondering what I should look for if I wanted to expand the collection. Will any Morse Taper 3 collet work?

I am new to this equipment so please go easy on me-

-Ed
 
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.
 
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.

It is hollow. Most of the collets are engraved "South Bend", the size, and "3". No other identification.
 
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
 
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.

I do not know the grip range for 3C, but 10 thou feels like it should grip.

Chattering when parting may not be due to the collet. So many variables can impact parting. Tool, relief angle, spindle speed, feed rate, type of metal, width of parting tool. I have often experienced chattering. More experienced forum members may have advise. I would look at some YouTube videos. Toms Techniques, Joe Pieczynski are two example channels.
 
Try not to go more than .005" off the nominal size to get a good hold. The closer to nominal, the better the hold.
 
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