Hello Roy!

Saturday November 22 2014 16:44, you wrote to me:

 KvE>>  Yes great, the same inch based spanners, but with Witworth tread, a
 KvE>> different pitch from the inch based UNF.

 RW> But the same as the 'inch based UNC' threads with, as you point out, a
 RW> different thread angle.  50° vs 60°...

 KvE>> There was another difference as well, the angle of the thread
 KvE>> flanks.

 RW> I don't understand 'thread flanks' - Would you be referring to pitch
 RW> angle? As in the example above.

 I don't know the different treads and their specifics by name. This is all
 from memories of the mid sixtie. But indeed one was a difference in thread
 angle as you mention above. The was also a difference of one tread/inch
 between two standards. To some extent these were echangeable as well.

 At the time I was an intern at engine revision company. Some of the engines
 were british made other were from US made draglines. Both used "exotic"
 threads. The machinery I used in my professional life was German built, so
 that was all metric.

 Pipe thread has not been converted to the metric system, apparently the
 pipes did not either.

Kees

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