Re: gEDA-user: PCB mounting holes for metric screws

[Dave N6NZ <n6nz@xxxxxxxx>]

For clearance drill, try googling "metric free-fit drill".

For the annulus, I like to be at least as large as a typical screw head. 
  I find the catalog at mcmaster.com to have lots of representative data 
for hardware.  Of course, mcmaster.com would be an expensive way for you 
to buy hardware where you live -- but the data sheets should serve you well.

-dave

Michael Sokolov wrote:
> 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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> 
> 


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