My father was a fitter and turner, diesel mechanic, farmer and self-taught panel beater. When I was a kid he worked on old British cars, Morris Minors in particular (he had a fondness for the early "split screen" flat head) as well as American and Australian made vehicles and machinery (much of which was war surplus from what the US left in Australia from WW2) so I was exposed to the vagaries of Whitworth bolt and nut sizing, compared to the American AF standard. Japanese equipment largely used metric as did Australia from the early 1970s.
Whitworth sizing made no sense. Only decades later did I realise that Whitworth is a measurement of the bolt diameter, while the distance across the flats of the bolt heads and nuts were some standardised mathematical multiple of that; and that AF wasn't an acronym for "American Fine" it was simply "across flats" which made finding the spanner to match the bolt much, much easier.
My father was a fitter and turner, diesel mechanic, farmer and self-taught panel beater. When I was a kid he worked on old British cars, Morris Minors in particular (he had a fondness for the early "split screen" flat head) as well as American and Australian made vehicles and machinery (much of which was war surplus from what the US left in Australia from WW2) so I was exposed to the vagaries of Whitworth bolt and nut sizing, compared to the American AF standard. Japanese equipment largely used metric as did Australia from the early 1970s.
Whitworth sizing made no sense. Only decades later did I realise that Whitworth is a measurement of the bolt diameter, while the distance across the flats of the bolt heads and nuts were some standardised mathematical multiple of that; and that AF wasn't an acronym for "American Fine" it was simply "across flats" which made finding the spanner to match the bolt much, much easier.