On 16 Jun 94 Mike Causer <mike@setanta.demon.co.uk> wrote:
>> Moss sells a cheapie set of open-end Whitworth. A bit clumsy but okay
>> if you your car only has a few and access is good.
>
> No, no, no. Whitworth have different head sizes to BSF, the spanners
> will not fit!
Not so. The jaw dimensions of Whitworth and BSF wrenches are the same,
but they are labelled differently. As originally designed (in the 1850's
if I remember correctly), Whitworth fittings had larger hex dimensions
than those on British Standard Fine fittings (which came along much
later). When the smaller-headed BSF standard was designed (early 1900's),
rather than make existing tools obsolete the designers just stepped the
hex head down one size relative to the shaft diameter. In other words, a
1/4 BSF bolt has the same size head as the original 3/16 Whitworth bolt,
so both use the same size wrench (3/16 W or 1/4 BS).
I have wrenches marked both ways, but generally I just ignore the marked
sizes and use the one that fits. Unlike American standard wrenches,
there's a larger difference from one size to the next, so it's easy to
"eyeball" the right size. For those who _must_ have all the details:
BSF Bolt Wrench
-------- ----------------
1/4 BSF 1/4 BS or 3/16 W
5/16 BSF 5/16 BS or 1/4 W
3/8 BSF 3/8 BS or 5/16 W
7/16 BSF 7/16 BS or 3/8 W
By WW2, most Whitworth bolts (renamed British Standard Whitworth or BSW)
used the same hex sizes as the corresponding BSF size (i.e. a 1/4 BSF bolt
and a 1/4 BSW bolt now have the same hex size). You aren't likely to run
into very many of the old large-headed Whitworth bolts unless you're
working on a pre WW2 car. However, for reasons best left to the
toolmakers to explain, wrenches continue to be made with Whitworth
markings as well as the more modern BS markings.
BSF and BSW fittings are (were?) also made in a 3/16 size, but it wasn't
used much on most British cars. Instead, "British Association" (BA) sizes
were used for applications requiring sizes smaller than 1/4. This is a
numbered size range (like American machine screws), starting at 0 (the
largest). The most commonly used sizes (in my experience, anyway) were 0
BA and 2 BA. BA fittings require BA wrenches. BS and W wrenches don't
fit.
> I'd be amazed if Moss didn't also sell BSF/BSC (coarse) spanners also,
> they have the same head sizes and are pretty well all you need for
> post-1945 LBCs. If you want the best in tools, Snap-On cover all of
> them.
Moss Motors sells wrenches marked in the old Whitworth sizes, plus
"ignition wrenches" in BA sizes. They're not great tools, but they're
good enough unless you use them all day every day. Snap-On are
_definately_ the best, although the old Craftsman wrenches (in Whitworth
sizes) were a close second and worth grabbing if you find a set in a flea
market.
By the way, BSC stands for "British Standard Cycle", not "British Standard
Coarse". The thread pattern is different from BSF and BSW, but standard
BS wrench sizes are used.
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Chip Old 1948 M.G. TC (TC6710)
feold@umd5.umd.edu 1962 Triumph TR4 (CT3154LO) (daily transportation)
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