One of the arcane bits of tooling requirement that I came across was for a 19/32" spanner for the cones and jam nuts on the wheel axles. Good luck finding one of those.
But 15mm spanners are readily available, and 15mm is just shy of 19/32"; like so:
19/32" = 15.08mm (i.e. 15mm + 0.08mm = 19/32").
What that tells us is that you only need to widen the jaws of a 15mm spanner by 8/100ths of a millimetre and you have a 19/32" spanner.
I have a 15mm spanner on hand, but it's a top quality one that I didn't want to mess with. The local bike shop had a two-piece set of medium quality cone spanners for $9.95 -- a 15mm and a 16mm. I didn't already have a 16mm, so I bought the set to get me a 15mm spanner that I wouldn't mind modifying, and a 16mm to add to my collection of useful standard tools to have on hand.
The spanner is made of pretty hard tool steel, but it's not file-hard. A few firm passes with a suitable mill file were all it took to get the spanner's jaws opened up a bit, and voila, a 19/32" cone spanner:
'Spanner' vs. 'Wrench'This is one of English's little quirks that has long puzzled me.
The words are interchangeable, really. The Brits seem to use the word 'spanner' for a wrench of any kind. In Canada and the USA, we use the word 'wrench' for most anything that one would think of as a more-or-less ordinary sort of wrench, reserving the word 'spanner' for specialized forms of wrench, such as these thin ones for bicycle axle cones and jam nuts.
In any event, I now have a 19/32" spanner/wrench/implement-for-dealing-with-Raleigh-cones/whatever.