According to Roger Shoaf :

"Richard J Kinch" wrote in message
. ..
There's an odd thread, called the Leica thread, that is used on
photographic enlarger lenses. It is specified as 39mm in nominal diameter
but 26 tpi in pitch.

I'm wondering what other monstrous metric-English combinations are out
there?

There some small watch screws that use this system, metric diameter and the
threads per inch.

And I think that microscope objective threads are typically
0.800"x some fine metric pitch.

Enjoy,
DoN.

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