# Help, Please, Need some info on Pratt $ Whitney (?) collets



## 110octane (Jan 17, 2015)

I am searching for the designation for some rather unusual (or so it seems) collets.  The collets look like the popular "3C" series used by South Bend, but they are not.  The collets have a body diameter of 0.650", with a 3/4" long threaded shoulder that is 0.625" X 24 TPI (5/8" X 24tpi is National Extra Fine.  The overall length of the collet is 3 3/16" (That includes the threaded boss).  These collets are marked "P & W" or "T" on the end.  They are not Pratt & Whitney 3NS (Standard Designation 3PN) because the length of the 3NS/3PN is 2 1/16 which is a full inch shorter.  Also the threads on the 3NS/3PN is 0.645" X 24 tpi.

These are not Stark No. 3 1/2 (Standard designation No. 32S) because, again the length is shorter on the Stark @ 2 9/16.  The threads on the Stark are 0.695 X 24 and the body diameter is larger @ 0.703"

I am fortunate to have an old edition of "Machinery's Handbook" that has a table of collets (popular in the 1940's?).  This table has nothing that matches these collets.  There are also some excellent collet dimension tables on the internet, but I have not found this one.  They must be something made by Pratt & Whitney, but that is not for sure and who made the one marked "T"?  There were a myriad of collets made over the years for watchmakers lathes and then the modern "ER" series as well as others. 

I have never seen a manual or handbook, etc. that lists all the patterns of collets manufactured over the years...   If anyone can help out with this I would be most appreciative.
Thanks, Geoff Morgan


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## raykehrhan (Jan 18, 2015)

looks like you are looking for Pratt Whitney 4PN Collets. What lathe or mill do you need collets for?

Ray


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## 110octane (Jan 18, 2015)

raykehrhan said:


> looks like you are looking for Pratt Whitney 4PN Collets. What lathe or mill do you need collets for?
> 
> Ray


 Thanks for the reply.  The collets are part of a collection of parts from an 11" Logan tool room lathe.  The 4PN are larger than these collets, and a bit shorter in overall length.  The 4PN has a nominal thread of 0.995" X 16 TPI, a body of 1.00" diameter and an overall length of 2 29/32".  The closer that came with the collets is a one piece tubular style with an integral wheel and a brass thrust washer.

I am going to inquire from Logan as to the linage of these.  Thanks again, Geoff Morgan


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