Lathe Chuck thread size

Lathe Chuck thread size

This topic has 4 replies, 5 voices, and was last updated 22 February 2025 at 11:22 by Howard Lewis.

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21 February 2025 at 16:55 #784798
Bootlegger Blacky
Participant
@bootleggerblacky
Hi everyone,I have a couple of old lathe chucks with a thread size of 7/8”.11 tpi.

any idea what machine these could be off?
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21 February 2025 at 17:59 #784807
jim1956
Participant
@jim1956
lathes.co.uk/bsw says a 7/8″ nose, no tpi mentioned just 7/8Whit.

How confident are you in the 11tpi, the normal 7/8 Whitworth would be 9tpi.

Regards Jim

Edited to add.

Just looked up 7/8″ BSF (same 55 degree thread form as Whitworth) but 11tpi.
21 February 2025 at 18:25 #784812
DC31k
Participant
@dc31k
There is a post here where someone says they have a Myford ML4 with a non-standard spindle nose that has that thread.

Myford ML4 headstock thread size

And one here which says Faircut Senior:

https://sites.google.com/site/mistergriffithsworkshop/past-projects/lathe-chuck-backplate
21 February 2025 at 22:28 #784858
peak4
Participant
@peak4
Search Tony’s site for 7/8″ BSF; here’s one result

https://www.lathes.co.uk/boxford/page5.html

Bill
22 February 2025 at 11:22 #784911
Howard Lewis
Participant
@howardlewis46836
The ML3 and 4 changed from 7/8 x 9 (7/8 BSW.) to 7/8 x 12 tpi (Whit form) over time.

Might be worth rechecking the pitch?

Howard
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