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SAE threads, are 60 degree. Whitworth threads, are 55 degree. A whitworth
bolt with a 5/16 dia. will actually interchange with a 5/16 NF.
Of Durf & Sue Hyson
Sent: Wednesday, December 19, 2007 1:54 AM
Subject: [Roadsters] [Fwd: Re: Was cleaning carbs / Now pre-ISO threads]
I've done it again ! Sent the reply to one poor soul !
At the risk of offending our old masters.... it was the British car
industry that had the greatest influence on post WW 2 Japanese car
companies. One of the first and most important execs to be involved in
rebuilding a Japanese car company was actually from Hillman. They worked
with Isuzu in the late 40's or very early 50's. Datsun and Austin were
next if I remember correctly. Fuji/Subaru also went down that path but I
don't remember with whom.
It is not a coincidence that we have Sumitomo DUNLOP tires , Hitachi
carbs that are patterned after SU's and early Japanese brake calipers
licensed from Girling complete with the "G" and fist. it is also why
most early Japanese stuff was built with SAE hardware. Once the Japanese
started designing their own parts you begin to see the shift towards
metric.I can remember changing a master cylinder on a Datsun once (I
don't remember if it was a Z or a roadster) and being surprised that the
bore was a SAE dimension and yet the threads on the pushrod were 8 MM .
As far as the Whitworth thing goes I have never seen any but anything is
possible. Whitworth stuff can usually be identified by the fact it
usually takes odd size wrenches. Also , if you look closely at the root
or tips of the thread they are round not pointy. That is the primary
distinction of Whitworth thread . Common SAE and metric stuff is wedge
form thread so the roots are vee shaped and the tips are a point. In
Whitworth the thread profile is like a sine wave. The root is a curved
fillet and the tips are rounded off.
> "What idiot used 32TPI on a bolt that size for!"
> My reply was the Japanese under strong American influence post WWII.
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