Unusual Crawford Collets and where to test them

[RainbowsParticipant @rainbows]

I recently liberated some Crawford Multibore collets from a shop just before they, and the rest of the shop contents, went into a 20 yard roro skip.

More fool me. They are all non standard.

Group 1 are labelled “J56” along with sizes and have a total diameter of ~102mm and total depth of 56mm.

Group 2 are labelled “HD” (heavy duty) “BB” (blackbar?) and one “757” along with sizes and have a total diameter of ~120 and depth of 75mm.

Group 1 are entirely off kilter from anything. Diameter of an E size but depth of the rare B collet. On the internet I found one mention of them 10 years ago of someone looking for them for his production lathe. Sized 22-66mm.

Group 2 are harder to work out because they closely match F / N-175 collets but are 5mm too short. The angle might also be different but being “heavy duty” collets with teeth for black bar that might just be to do with the preload on the springs. 45-69mm hex and 69-75mm round.

Loathe to throw away 25 good collets, some still new in box, is there anyone in the Sheffield area with a chuck that takes Crawford E / T-285 and/or F / N-175 collets? I’d like to try them in a chuck and see if they hold true and accurate.

I think group 2 will work in a standard chuck but don’t want to sell on false goods.

Group 1 is less hopeful. But if they at least click into a standard chuck that tells me they use a 15 degree taper and one day, no time soon, I might custom make a collet chuck to take them.

 

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