"whit3rd" wrote in message
...

If it measures M3 x 0.7mm, the 5-40 thread, at M3.175 x 0.635mm is
the
closest. You ought to at least buy a few and try that size...

Taps make pretty good thread gauges for both holes and screws. They
don't need to be good or expensive to clean up old tapped holes.

Does the thread match that of an M4 x 0.7 screw when you hold both
together in front of a light?
-jsw