gEDA-user: PCB mounting holes for metric screws

[msokolov@xxxxxxxxxxxxxxx (Michael Sokolov)]

Hello fellow gEDA/pcb users,

I've got a PCB mechanical design question.  I have given up on the idea
of copying the form factor of EN routers (basically I don't really like
that form factor) and I'm going for a form factor of my own.  However,
being a proud citizen of the Union of Soviet Socialist Republics, I want
to make my form factor all metric -- the Soviet national standards body
required that for all new designs and my own sense of taste does the
same. :-)

I've speced my board dimensions in metric (130x165 mm) and I'll have
mounting holes for metric screws, some M3 and some M4.  My question is
about the latter:

I've been told that the drill diameter should be 3.1 mm for an
M3-accommodating PCB hole and 4.2 mm for an M4-accommodating one; is
this correct?

But what about the copper annulus?  What would be a good copper annulus
for those screw-accommodating holes?  Assume the "typical" kind of screw
used to secure PCBs to enclosures.

TIA,
MS


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