[Healeys] Threading

[Peter Svilans]

Bernard,

I'm aware of the French official adoption of the Metric system in 1799 "For
All Men, For All Time".   I'm referring to much more specific "commonly used"
and "obsolete" applications of Metric, both equally valid.

Old French Standard and modern ISO Metric both have a 60 degree thread form,
but the pitch is sometimes different.  A modern 8mm bolt normally has a pitch
of 1.25 mm, while an old French 8mm bolt has a pitch of 1mm..  The majority of
bolts used in the XPAG/ XPEG MG engines are 8x1mm but since this is an
obsolete type you won't necessarily find them at the local nut & bolt place on
this side of the pond when you ask for metric.  They CAN be found, but it
usually means dealing with a specialist firm like our Spae-Naur company here
in Canada.  I've run into this problem many times over the years while
restoring the old French and German microcars from the forties and fifties for
the museum: ( http://www.microcarmuseum.com/tour/messerschmittkr201.html )

Canada's been Metric only since 1972, and the switchover has been been
reasonably complete, except for some of us old fogies who continue to use
'miles per gallon' instead of 'litres per 100km'.

Best
Peter