Clarkson Collet Threads?

[Steve Taylor 2Participant @stevetaylor2]

Does any one know which threads are are used in the clarkson small S type collets, metric and/or imperial.

I need to make an arbor to carry a small horizontal cutter which I would like to hold in a Clarkson collet.

I’ve tried BSF, BSW and Metric and 3/8 UNF, none of them are right

[Steve Taylor 2Participant @stevetaylor2]

[Tony Pratt 1Participant @tonypratt1]

Google search provides the information that the thread is 20 tpi for all sizes with a Whitworth form.

Tony

[mgjParticipant @mgj]

Tony is correct, but they are specifically slightly undersize – .003 to .006. The centre is 3/16. You need to make the shank of your arbor +0 to -.001 on dia.

 

Its all in The Model Engineers Handbbook, thread lengths etc, so its pretty easy to do. .

[Steve Taylor 2Participant @stevetaylor2]

OK, I think I’m missing something here.

Yes its fine if you thread a 1/4″ bar with a 1/4″ BSW die as its 20TPI, and it screws into the 1/4″ Clarkson collet perfectly.

 

However if I need to use a 3/8 or 1/2″ bar, and collet, the TPI is 16 & 12 respectiveley.

[chris stephensParticipant @chrisstephens63393]

Hi Steve,

What the others have said is that the threads used by Clarkson are their own standard and not BSW, BSF, UNF or whatever. This means you are stuck with screw cutting your arbours or failing that you will have to go to Tracy Tools who list both 3/8 and 1/2 X 20 dies.

Personally I would screw cut, as it is easier (to get accuracy), quicker and cheaper.

chriStephens

[Steve Taylor 2Participant @stevetaylor2]

Hi Chris, thanks for explaining that for me. I dont have screw cutting facilities, my biggest lathe is a Schaublin 102 plain centre lathe but at least I can try the Tracy tool route.

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