This is how I drill M42 lenses to accept the Pentax locking pin. The jig is a dead ME Super front plate with the lock pin removed, then I use the hole to guide a drill.
This picture is just for illustration - when used in anger I clamp the flanged bit of the camera body in a vice so the whole thing sits horizontal, I tape the back of the lens to keep the crap out, and drill a shallow hole - maybe 1.5mm deep - with a hand drill to ensure good control.
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drilling 2 par
David Lloyd, on ipernity[/IMG]
( No working or valuable cameras were destroyed in making of this jig
)