Collets for WW pattern lathes are all deceptively similar in shape and size but there are differences among the different makes (particularly among vintage make).
As you can see in the following table there are slight variations in the thread pitch and diameter. 0.275" x 40 TPI is probably the most common. Taps, dies, and drawbars are readily available for this size. When shopping for collets the generally recommendation is to take your drawbar with you and test fit any collets before you buy.
The 7 x 0.75mm is a standard metric thread as is used by the Chinese (and possibly other Asian) collet manufacturers. Universal drawbars to fit this thread are available as well.
The table below is from information published at various times in the tools forum.
As you can see in the following table there are slight variations in the thread pitch and diameter. 0.275" x 40 TPI is probably the most common. Taps, dies, and drawbars are readily available for this size. When shopping for collets the generally recommendation is to take your drawbar with you and test fit any collets before you buy.
The 7 x 0.75mm is a standard metric thread as is used by the Chinese (and possibly other Asian) collet manufacturers. Universal drawbars to fit this thread are available as well.
The table below is from information published at various times in the tools forum.
| Body MD | Body Length | Tread MD | Pitch (mm) | TPI | Brand | |||
| |mm||inch||mm||inch||mm|||||| | ||||||||
| 0.314||7.98||||||0.268||6.81||0.625||40.64||Boley | ||||||||
| |||||||0.275||6.985||0.635||40||Levin | ||||||||
| |||||||0.275||6.985||0.625||40.64||Lorch | ||||||||
| |||||||0.27||6.858||0.635||40||Wolf-Jain | ||||||||
| |||||||0.268||6.81||0.625||40.64||Adams, Boley-Leinen, Coronet, Derbyshire, Pultra | ||||||||
| |||||||0.269||6.82||0.625||40.64||Schaublin, Favorite II, Favorite III | ||||||||
| |8||0.75||19||0.275||6.985||0.635||40||Modern Starrett | ||||||||
| |7.9502||0.75||19||0.275||6.985||0.635||40||Sherline WW | ||||||||
| |8||0.75||19||0.276||7.000||0.75||33.87||S-96 ATM-3 | ||||||||
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