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From:	karl AT aspodata DOT se
To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] pin drill and thickness statistics from cvs.gedasymbols.org
In-reply-to:	<5A6B59B4.1050508@xs4all.nl>
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Comments:	In-reply-to "Bert Timmerman (bert DOT timmerman AT xs4all DOT nl) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
	message dated "Fri, 26 Jan 2018 17:39:16 +0100."
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Date:	Mon, 29 Jan 2018 15:04:46 +0100 (CET)
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Bert:
> karl AT aspodata DOT se wrote:
> > Do theese thickness diameters look reasonable ?
...
> > hole      c     b     a    aa
> >    0.3   0.8   1.0   1.2   2.5
> >    0.4   0.9   1.1   1.3   2.7
> >    0.5   1.0   1.3   1.5   2.9
...
> - determine lead dimensions and shape (round, square, flat, etc.),
>
> - determine required hole diameter and define in footprint file,

Ok, I use:

 my $drill = 0.2 + int(1.01 * $lead_dia * 10 + 0.9) / 10; # round up

wich works for single leads.

> - based on minimal, nominal, maximum accuracy (soldering technology) 
> determine drill sizes of board house (round up and use the "even" values 
> as in .022, ,024, .026, etc).
> 
> - use drill sizes that exist and are actually sold by drill manufacturers !

Ok, 0.1 or 0.05 steps are fine here. Don't know what drill sizes are 
available in the US.

> - after layout is finished look at the drill report and optimize for 
> minimal drill bit changes.
> 
> - so .020, .022, .024, .026, .028  all end up being .028 when the files 
> are sent to the board house for production.

Nice idea, thanks.

> - routing goes into a separate (gerber) file ... and do communicate with 
> the vendor before actual production starts up.
> 
> - YMMV to the gallon ;-)

Aww, you get farther since we measure by the litre.

Regards,
/Karl Hammar

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