Hi All
If you are confused with all this talk of thread types and bolt head sizes etc, it gets worse!
Crossely's of Manchester, who used to make cars and trucks and engines for small ships and railway engines, in the late 1950's onward they manufactured French Pielstick Marine Diesels under licence. The original French engine of course was all metric and used metric bolts which had large hexagons. The Crossely built engines used metric bolts but with generally a Imperial A/F sized head, though there were some larger sizes which still used a whit. based sized spanner. Presumably the use of imperial sizes was due to the British ships in the 1960's, were not normally equipped with metric spanners as a rule, and of course the metric ISO standard metric bolt had not come into general usage. On the ship over the ensuing years, replacement parts were needed and not necessarily sourced from Crossley's but from other suppliers, which led to the odd metric headed bolts creeping in, then of course there was the choice of large headed metric bolts and the auto type bolt with a smaller hex. head. Being that the vessel was built in a British yard, things like pipe flanges may have had Whit/BSF or UNC/UNF Bolts fitted when new, as But over the years some flanges even ended up with a mixture of both. So whatever you job had to do on board required a bucket full of spanners of every shape and size. Thank god they did not have any Douglas sized threads to deal with, it was bad enough dealing with the common thread types and the variation in bolt head sizes.
Cheers SteveL.
