On Sun, Feb 19, 2006 at 02:10:21PM -0500, Olin Lathrop wrote:
> Tomas Larsson wrote:
> > Imperial is a pain in the arse, when it comes to PCB design.
> > It seems that most editors has imperial units as base units in the
> > database, and that creates round-off problem when working in metric.
> > Since most Chip manufacturers is moving from imperial to metric it
> > creates a problem.
> 
> All CAD where I've looked into this use an integer representation that is a
> sub-multiple of both mm and mil.

Using 0.1mm as your base unit would do you just fine as the inch is
defined as exactly 25.4mm.

That said real machining can easilly go down to tolerences as tight as
+-0.01mm, so you'd want am much smaller base unit than 0.1mm.

-- 
pete@petertodd.ca http://www.petertodd.ca
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