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Re: gEDA-user: New Column: From the CAD Library



On Sun, 2011-02-06 at 10:55 +0100, Bert Timmerman wrote:

> One of Tom's "issues" that is to be kept in pcb are most of the mil grids
> because of the bazillion perf board and mil based parts on the market, to be
> bought for cheap by hobby-ists, or for "Quick-and-Neat" proto boards (we
> don't play or do dirty ;-).
> 
> Just my opinion on the subject.

Imperial parts are not a problem for a sufficiently fine metric grid. I
don't think we should remove the option of working on a Mil grid though.
I do it most of the time, even though I realise it is a habit best got
out of.

Way forward:

Metric "nm" grid internally, parts defined in whatever units the
vendor's controlling dimensions are in.

This might require relative origins to be used between the part design
coordinate and the board's snap-grid, but that seems to be mandated by
various IPC standards anyway.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)

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