> I'm aware that Whitworth _threads_ are different than the now more common
> SAE
> and metric threads that bind the bolts and nuts of the rest of my life,
> and I
> have accumulated small stash of the 58 degree buggers just in case. I
> realize
> that a set of taps and dies would be useful for any work on my sidescreen
> cars, but special Whitworth wrenches and sockets?
>
> I see at http://www.samstagsales.com/whitworth_table.htm that an SAE
> wrench of
> 7/16 size would be used on a 3/8 Whitworth bolt. Other than the naming
> convention (and the few odd-sized Whitworth bolts that lack an SAE
> counterpart), I assume that SAE wrenches would work just as well to remove
> and fasten Whitworth bolts and nuts? Yes?
>
Hoyt:
I believe you may have misinterpreted the table. In actual fact, a 7/16 SAE
(sometimes known in the UK as Unified, or AF) wrench will not fit a 3/8 BSW
bolt. Their are several differences in nomenclature between the two
systems, as well as the difference in thread form. The biggest difference
is that British Standard Whitworth (BSW) and British Standard Fine (BSF)
wrenches are identified by the bolt size they fit, not by the width across
the flats of the bolt head, which is how an SAE wrench is identified. It is
further complicated by the fact that the BSW and BSF bolts of the same
diameter will not have the same sized heads. I believe that the universal
rule is that a BSF bolt will have the same head size as the next smaller BSW
bolt (although there may be exceptions to this rule that I am not aware of).
Thus, a wrench for a 3/8 BSW bolt will also fit a 7/16 BSF bolt, but the
width across flats is 0.71", which is a little under 23/32". There is no
SAE wrench of this size. I believe the "British Standard" in the table is
actually referring to BSF.
My advice would be to buy a full set of BSW wrenches simply because you can
never have too many tools! Then, when you buy your Triumph Dolomite you'll
be fully equipped to fix it. It's not a good idea to use an ill-fitting
wrench on a bolt because you stand the chance of rounding off the bolt as
well as rounding off your knuckles. For the same reason, I will only use a
crescent wrench on any bolt as a very last resort.
By the way, the thread on a BSW or BSF bolt has an included angle of 55
degrees, not 58.
Michael Marr
1960 TR3A
Naperville, IL
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