On Fri, 4 Jul 2008 08:54:11 +0100, "nightjar" cpb@insert my surname
here.me.uk wrote:

That was rather the point of the Unified thread - to provide something that
would work with both British and US standard threads, to improve
interchangability between allies during the war.

Actually it was _after_ the war. The Unified standards weren't agreed
until 1949, as a response to problems during the war. They weren't fixed
at the time because the disruption to production would have been
immense.

During the war itself the US kit used American National standards,
previously known as United States Standard. Nothing inter-worked with
British kit. For some kit, such as the Sherman Firefly, this literally
meant one set of spanners to work on the (British) gun and another set
of wrenches to work on the US-built chassis and engine.