In article ,
Sylvain VAN DER WALDE wrote:
Nuffield group used oddities for some things - cycle threads with BSF
hexes. Could be those threads are close to metric fine. First really
noticed them as big end bolts on an MG XPAG engine.

I wasn't completely sure about this. You probably are correct (the clue
being in the English spanner sizes). The threads were certainly very
fine. Now BSF isn't a particularly fine thread, so using a Cycle thread
may not have been such an odd thing to do, after all

The story I was told by my father was that Morris originally made cycles.
And at that time many such engineering shops made bolts and nuts in house.
When they started making cars, they carried on with the same threads to
avoid the capital cost of buying all new stocks and dies, etc. But changed
the hex to BSF sizes so the local blacksmith had tools that fitted.

Could all be an urban myth, though. But he did serve an engineering
apprenticeship at about the time Morris started making cars.

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Dave Plowman London SW
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