[Mini] Thread size

[John Lieberman]

Do any of you happen to know the thread pattern for the water 
temperature sending unit that screws into the head on an A+ 1275?

I bought some Bosch electrical gauges -- water temperature and oil 
pressure -- for my '81.  But, when I unscrewed the old Smith's water 
temperature sending unit and tried all of the adapters that came with 
the Bosch gauge, none of them matched the thread pattern.  So I'm 
thinking it must be metric.  Since I'm a Yank, I know a lot about SAE 
threads but I don't know much about metric threads.  I'm thinking it 
might be M16-1.5, but that's just a guess.  Can anybody shed any light 
on this subject?

Thanks a bunch

John