On Sat, 15 Sep 2007 22:23:52 -0500, Richard J Kinch wrote:

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?

Campagnolo bicycle axles. 9 and 10mm x 26tpi.