Re: 3C vs 6K

Jim B. <btdtrf@...>

I have a 10K spindle in my 9” Workshop headstock.


I do use 6K/3C/3AT collets.

I do not have a speed closer. I do have 3 handwheel closers.

The 3C and the 3AT have essentially the same threads but the 3AT is shorter, a bit larger in diameter and has a different taper than the 3C.

I have two POT collets for 3C.


I see no reason you could not make a tube for the 3C to fit your speed closer.

You would need a taper adapter sleeve for your lathe, to take 3C if you do not have one and a Nose piece if you do not  have one


Now a once in a lifetime offer.


I have a brand new 6K pot collet. Never used. It’s a big one, 4-1/2 OD.

I will probably never use it. I have had it since about the time SB had their going out of business sale.

I would be willing to part with it. I am getting old and need to start clearing stuff out.

Not inexpensive but if you are interested contact me off line.


I also have 3 6K SOFT steel collets; a 1/8 a ½, and a 9/16” (9/16 could be 35/64. All are unmarked.

They say Modern, 6K, soft.


I think you could just turn a shallow 1” ring in them. The OD seems to be 1-3/16 (1.178), the key is 0.080 deep.

The ring might break through the key.


Perhaps one of these would do better; I would guess the 9/16 one could work.

These would be cheaper.


Jim B.

From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...] On Behalf Of David Rysdam
Sent: Tuesday, April 01, 2014 1:52 PM
Subject: [SOUTHBENDLATHE] 3C vs 6K



For my decoder ring project, I think I want to use a pot collet (why are
they called that?) to clean up the back sides after parting. But I don't
want to chase down and pay for a 6K one.

In the mailing list archives, I find claims that the 10K spindle can
take a 3C collet, although you need a different closer because of
non-matching threads. (Online I've found claims that the collets are
totally different, but I guess I can trust the SB mailing list over some
guy on PM.)

However, I have the speed closer and I'd prefer not to give that up. Is
there an easy way to non-destructively modify that to be both 3C and 6K?
Can just the tube be replaced? This would be especially nice if I do a
mini-run of ~5 pairs of rings, which would be 30 pieces of similar
diameters. Wouldn't have to crank the handwheel all those times for each

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