Thread: Imperial Measurements Explained

Originally Posted by Lionelgee

Hello All,
........

Now all I have to do is hope that it is all good information and that people don't post up a flurry of corrections

Kind Regards
Lionel

Only real corrections I could spot was the table for wheel nut sizes - Series Landrovers changed the spanner size 1n about 1970, not 1972 (but not a sudden change!), and the earlier size is not 15/16" or 24mm, - it is 9/16" BSF (although the others will work).

Additional information - BA, although a very old and effectively obsolete thread, it is actually a metric thread, but with a narrower thread angle.

Whitworth is the oldest thread standard, and in most sizes UNC has the same threads per inch although interchanging the two is poor practice as the thread form is slightly different.

Although you are unlikely to come across them, in the nineteen twenties, thirties and even later, some popular engines used metric (French, not ISO) with Whitworth bolt heads and nuts. These were used on the DH Gypsy series aeroplane engines and on Morris car engines from 1919 into the thirties.

John