Exhaust valve dimensioned in, gasp, inches?

[DeWitt Harrison]

Folks,

As part of my Type 44, 10V Science Fair project, I made some
very careful measurements (+/-.01 mm) of an exhaust valve stem.
To my great wonder, it was dimensioned in inches to wit:

   stem diameter = 7.94 mm ( 5/16" )
   keeper groove diameter = 1.59 mm ( 1/16" ) - 3 places
   lands between grooves = 1.19 mm ( 3/64" ) - 2 places
   stem tip to first (top) groove = 1.98 mm ( 5/64" )

This isn't like 13 mm is close to 1/2". The dimensions are
dead nuts on fractional inches. Ya don't suppose Audi
bought them there sodium filled valves from TRW do ya?

DeWitt Harrison
Boulder, CO