Andy Millar:
...and given that no-one on eBay sells the UNC nuts I'm after in the UK anyway (I only need a handful), I'll try BSW and see what happens! Being brass screws they probably are BSW anyway. Brass screws do seem to be the last bastions of imperial threads in the UK, I guess because the threads tend to be coarser. Or because most of us who use brass fixings a lot tend to be terribly old
Are the cupboard door knobs American? 99.9% of things with UNC threads are American. If they are British then they will be Whitworth. There is some truth to what you say about the coarser threads in soft metals.
Brass screws with UNC threads do exist but they are uncommon. Probably because of the American cost cutting culture. Titanium screws with UNC threads are quite common as they are used in aerospace.
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