OK, here is the official skinny on Whitworth. Source: Machinery's
Handbook, 20th edition. Have you ever seen a machinist"s toolbox?
There is a deep drawer in the center top. It has a
silver-dollar-sized hole in the bottom. This drawer is made to the
dimensions of this book. The hole is for you to stick your finger up
through to push the book up so you can get it out. Some of you will
think this is a gag, but I am confident that there are plenty of you
that know it is perfectly true. Anyway, I suddenly remembered that
I have such a box and such a book. Strictly speaking, only the
coarse threads are British Standard Whitworth, the same diameters and
wrench sizes are used in British Standard Fine. Here is a small
portion of the chart. Don't forget that the wrench is called by the
bolt diameter, not the actual wrench opening.
Bolt Diameter Across hex flats
maximum minimum
1/4 .445 .438
5/16 .525 .518
3/8 .600 .592
7/16 .710 .702
1/2 .820 .812
9/16 .920 .912
5/8 1.010 1.000
3/4 1.200 1.190
All dimensions are in inches. A 5/15 Whitworth wrench will work for
the fill plug on the Armstrong lever shocks on the front of a
Spridget. This plug is a 5/16-22-BSF bolt. The wrench will also
work for a bolt of 5/16-18-BSW. If there is such a thing as a regular
inch wrench of 17/32, that should work OK, as 17/32 = .531, but my
local tool supplier says not to hold my breath for that. I think I am
going to order a 5/16 Whitworth combination wrench from Moss. There
does not seem to be a point to ordering a whole set, as most folks
tell me you don't find Whitworth on Spridgets. Guess they didn't have
to fill the front shocks!
phile@pwcs.stpaul.gov
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Login name: phile In real life: Philip J Ethier
Phone: 298-5324
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