Subject: Collets for MT 3 spindle

From: [email-masked] (Tim Jensen)
Date: Thu, 23 Mar 95 04:28:21 GMT

I have a model 815 Logan lathe that I would like to equip with collets
and closure. The headstock spindle is threaded 1 1/2  8 t.p.i. with a
number 3 MT. Obviously 5C collets are too big for this spindle. What would
be my best choice for collets for this lathe? 

  Thanks, Tim Jensen

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From: [email-masked] (-F.KERFOOT)
Date: Thu, 23 Mar 1995 17:52:43 GMT

In article <[email-masked]>,
>be my best choice for collets for this lathe? 

Based on our recent discussion of the collets and spindle taper of the
South Bend 9" lathe, I expect that 3-C collets, as used in the 9" SB,
would be a reasonable choice. You might well be able to use the collet
closing sleeve from a 9" SB, which would be #3 Morse on the outside
and 3-C collet profile on the inside. The 9" SB also has a 1 1/2"-8
spindle thread, so the thread protector/closer remover from a 9" SB
may well also work. Using a 9" SB handwheel and drawbar tube would
depend on details like the spindel length and the bore through the
part which does not have the #3 Morse taper. 9" SB's are relatively 
common, so you may not have too much trouble finding the parts,
although their popularity may also make the parts more expensive.
3-C collets should not be too hard to find, although not as common as 5-C.

Frank Kerfoot
[email-masked]

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From: [email-masked] (Mike Rehmus)
Date: 23 Mar 1995 20:19:53 GMT

>be my best choice for collets for this lathe? 

Acorn collets or the double- angle collets made in Israel by ETM.  They 
each have twice the range of a 5C collet and are much shorter (same grip 
length though).  Rutland Tool lists 3 MT kits:

Model ER-32 for $386 that includes the 3 MT chuck holder and a set of 11 
collets from 1/8" to 3/4".

Model ER-40 for $570 that includes the 3 MT chuck holder and a set of 15 
collets from 1/8" to 1".

Or you can do what I did which is to make an adaptor that screws on the 
end of my lathe spindle and internally accommodates the back taper of the 
collet series I chose and an external thread for the ETR clamping nut 
that I bought from Rutland (cost about $50 with nut and wrench.)  Then 
each collet costs me $20.

The TIR is less than .001 four inches out from the collet on 1/2" stock.

Oh, BTW, my setup does not prevent me from using the full diameter of the 
spindle bore.

Best,

Mike

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From: [email-masked] (Ken Moonitz)
Date: Thu, 23 Mar 1995 17:39:40 GMT

>be my best choice for collets for this lathe? 

I would check out one of the collet chucks advertised in HSM.  They
use 5C collets which are cheap compared to 3C or AT collets.  Also 
you would not be limited to the spindle bore.