Spanners

I had asked in another thread but I don't want to hijack it and veer away from their own question.
A lot of mention goes on about AF spanners and SAE spanners, nothing to do with thread sizes however. Are AF and SAE the same thing when getting a set of spanners? Are these both your standard 1/4", 3/8", 7/16" stuff that you pick up at any shop?

Cowboy Don said:

Are AF and SAE the same thing when getting a set of spanners?

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SAE (Unified) fasteners have Imperial hexagons which graduate in size by fractions of an inch-therefore it follows that Imperial "AF" tools fit SAE/Unified fastener hexagons, so yes, however Imperial AF tools are also used for other non-SAE applications (such as pipe fittings etc.) so AF and SAE are not exactly "one-and-the-same" thing.

Also be aware that the fasteners they used have different thread count's per inch and angles. It is important to know which fastener to use, as some look close, but will bugger up your threads.

RSR

Whitworth wrench sizes refer to the bolt diameter, not the across-flats measurement. I'm going from memory here, but I think the old formula, when most fasteners were mild steel, was 1.25 x bolt diameter + 1/4". As alloy steel bolts started to become readily available it changed to 1.125 x bolt diameter + 1/8".

A lot of folks get a surprise to see how big a 3/8 Whitworth wrench actually is!