On Wed, 28 Jan 1998 12:53:41 -0800 Paul.Kile@Aerojet.com (KILE, PAUL D)
writes:
>
>If we are talking about fastener head sizes, there are only a few on
>the B which use Whitworth (or British Standard) wrenches. British
>Standard head size is similar to Whitworth head size, but differs by
1/16"
Boy, if people weren't confused before, they sure will be now. See
http://www.team.net/sol/tech/whitworth-hist.html for a full discussion of
this. However, to sum up, the British used shank size not head size to
denote the sizes of their wrenches. British Standard Fine altered the
head size on a particular size shank. The result is that a BSF Wrench of
3/8" will fit the same nut as a British Standard Whitworth (BSW) 5/16"
will fit. I guess this is what Paul means by a difference of 1/16". SAE
wrenches will only fit BSF or BSW by accident, since they are sized by
the size of the head of the bolt. BTW, Whitworth threads are different
from BSF threads and are not interchangable, although the wrenches will
fit. Confused yet?
>Part of the confusion is that the old Whitworth head measurement
>became known as British Standard (BS). This is entirely different from
the
>modern thread pitch known as British Standard Fine (BSF). BSF is for
>all intents and purposes the same as the SAE's United National Fine
>(UNF). That's why you can go down to the local 'Murrican hardware
>store and find bolts whose thread size will work on a B.
Eeewww. Where do I start? Ok, see above concerning "head measurement"
as regards Whitworth and BSF. Now, let's go to threads as a separate
issue. BSF threaded bolts are only found with BSF heads, however, as
stated above, a Whitworth wrench will fit exactly, but it will have a
different size marked on it. However, BSF threads are NOT the same as
SAE or UNF threads. If you try to put a BSF bolt in a UNF or SAE (or
vice versa) it will not fit. UNF is the SAE standard that British cars
went to in the 50's and 60's. The MGA and younger MG's had mostly UNF
(same as SAE) threads with some exceptions, mostly related to fuel lines
and brake lines.
>Clear as mud? I hope so, because this should be enough BS about BS!
Wait a minute!! We haven't even discussed Nuffield's Mad Metric, which
are the Whitworth-headed non-standard metric threaded bolts found in
pre-1956 MG engines! And what about British Association (BA)? And
British Standard Pipe (BSP)?
The net of all this is, if you have an MGA or MGB, don't worry about it.
If you have a TD or earlier car, you'll lie awake nights trying to figure
it out.
David Littlefield
Sleepless in Houston, TX
'62 MGA MkII (UNF and some BSF)
'51 MGTD (Whitworth/metric, BSF, BA, and UNF (but I'm not tellin' where))
'88 Jaguar XJ-S (Grace, space, and replace)
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