Subject: Whitworth/BS Spanner Sizes

From: [email-masked] (Tony Chabot)
Date: 4 Dec 1996 19:23:12 GMT

I realise that the size of a Whitworth/BS spanner refers to the diameter of the 
threaded part of the nut/bolt that ir fits, but does anybody know the 
relationship between that figure and the size of the nut/bolt head ? The 
across-flats and across-`diagonal' sizes do not fit nicely into Imperial 
fractional measurements.

Tony Chabot

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From: Robert Bickers <[email-masked]>
Date: 5 Dec 1996 00:23:50 GMT

>across-flats and across-`diagonal' sizes do not fit nicely into Imperial 
Whitworth derived "his" thread by averaging the thread pitch and thread form from several/many 
 shops in England, perhaps he averaged the head size as well. Cheers Bob