Odd collet

[Jim F]

I got a collet with some 3C's I bought, it is not a 3C.
Close, but no cigar........
Taper is 20 deg., not 12.
thread is .780x 24 tpi.
thread length is .620.
shank is .751
Length from the end of the thread to the taper is 1.16
Top of the taper is 1.963
length of taper is .550.

Anyone have an idea on what it is ?

 

[frankly2]

Pic would help, may be an AT

 

[graham-xrf]

The first thing I thought to do was convert the measures to mm. It still does not quite make sense.
0.550" = 13.97 mm That's three hundredths mm or 0.0012" away from 14mm.

Top of taper 1.963" = 49.860mm. That's quite close to 50mm
.. and so on.

Agreed that it is a bit of a mystery!
[Edit: There is a Sherline collet, known as "WW", which has a 10°per side taper. It's a long shot because those Sherline things are usually 40 TPI]


Does it look like this one?

 

[Jim F]

Pic would help, may be an AT

Wrong taper and threads for a 3AT.

 

[Aaron_W]

The first thing I thought to do was convert the measures to mm. It still does not quite make sense.
0.550" = 13.97 mm That's three hundredths mm or 0.0012" away from 14mm.

Top of taper 1.963" = 49.860mm. That's quite close to 50mm
.. and so on.

Agreed that it is a bit of a mystery!
[Edit: There is a Sherline collet, known as "WW", which has a 10°per side taper. It's a long shot because those Sherline things are usually 40 TPI]

View attachment 403923
Does it look like this one?

WW are watchmakers collets, WW = Webster Whitcombe, Sherline just makes a drawbar and adaptor for their lathes as well as making their own WW collets. My Sherline WW collets fit my 100+ year old WW style watchmakers lathe.