Re: gEDA-user: PCB pin hole size

[Wojciech Kazubski <wk@xxxxxxxxxxxxx>]

Dnia poniedziałek, 24 stycznia 2005 15:51, Walter Fetter Lages napisał:
> Wojciech Kazubski wrote:
> >   Hello.
> >
> >> There are many PCB libraries (m4 style) where components have pin hole
> >>size=20 mil. This is too small for typical pin-through-hole components,
> >>isn't it? Would 28 or 35 mil holes be better, or am I missing something
> >>here?
> >
> > I think that 20mils hole was used to serve as drill guide for manual
> > drilling. Even today it is usefull for fast prototyping of simple single
> > sided circuits, there are some technologies that allow making pcb from
> > laser printout in half an hour or so.
> > It would be better to make holes right size in footprint, but the option
> > to reduce all holes on postscript printout would be still usefull (at
> > least for some hobbyist). It should not be hard to implement.
> >
> > Wojciech Kazubski
>
>  OK, but I think that it would be better to have the footprints with
> correct size holes and leting PCB create a drilling mask file, with
> crosses at hole centers.

This requires extra step of punching each pad unless you have a professional 
drilling machine. A small hole in the pad creates a pit that helps to 
properly position the drill.
Ability to reduce holes would be usefull also for those who have to use 
postscript to cerate masks. 

Wojciech Kazubski