John G wrote:
"JR North" wrote in message
.. .

My '70 Datsun Roadster has some bolts that are 6.5mmX28tpi. Took a
while to figure that one out.
JR
Dweller in the cellar

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?

Tyre Sizes are mostly given (cast into the rubber) With the wheel
diameter in inches and the tread width in millimetres.

There was the unfortunate era of "soft metric"
where the diminsions of an "inch" part were
simply converted to 3-place metric and called
metric.

Lead to all sorts of ugly roundoff errors for
the designer that allowed the tolerance to build up.

Although not quite the same, US aviation uses
a very strange hodgepodge mix of units..

Statute miles for visability
Nautical miles for navigation
Degrees Celsius for temperature
Inches of mercury for atmospheric pressure
Knots for horizontal speed
Feet per minute for vertical speed