[Healeys] 100 Generator Witworth bolt

[Bob Haskell]

Gary,

There are two BSW standards.  Originally, the head of a BSW bolt was one 
size larger than the same diameter BSF bolt.  So for a 1/4" BSW bolt, 
the distance across the flats can be either 0.525" or 0.445".  5/16" BSW 
is either 0.600" (old standard) or 0.525" (new standard).  On some 
wrenches you'll see both markings (1/4" BSW, 5/16" BSF).

Source: https://en.wikipedia.org/wiki/British_Standard_Whitworth

Cheers,

Bob Haskell
Austin Healey 3000 BN7/BT7 registrar

On 1/18/21 3:03 PM, warthodson--- via Healeys wrote:
> Sorry for the spelling error (Whitworth not Witworth). As soon as I 
> read my email it was obvious to me.
> Gary Hodson
>
>
> -----Original Message-----
> From: warthodson--- via Healeys <healeys at autox.team.net>
> To: healeys at autox.team.net <healeys at autox.team.net>
> Sent: Mon, Jan 18, 2021 10:16 am
> Subject: [Healeys] 100 Generator Witworth bolt
>
> After our recent discussion about the 5/16" BSW (Witworth) bolt that 
> threads into the aluminum end plate on the generator, I decided to 
> search thru all my ziplock bags of British bolts to see if I could 
> locate that one bolt. My 100 shipped disassembled. First, I separated 
> all the 5/16" X 18tpi (coarse) bolts from the rest. Then I separated 
> all the bolts with heads that fit a 1/2" socket because I understood 
> that the 5/16" BSW bolts have a larger head. I was left with 2 bolts. 
> They are identical, except that one is about 1/2" long & the other is 
> about 7/8" long. Neither has any markings on the head of the bolt.
> My questions are:
>
> If one is for the generator, where does the other one go?
>
> The hex head on both bolts fit a King Dick socket marked 1/4W. The hex 
> head measures 0.52 across the flats. According the a "Key to Nut & 
> Bolt Sizes" chart I have, this head size should be on a 1/4"W bolt but 
> the bolt is 5/16" diameter X 18TPI. Do you see the contradiction? 
> Also, this chart indicates the hex head should measure 0.60 across the 
> flats for a 5/16" BSW bolt.
>
> Gary Hodson
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