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Date:	Fri, 26 Jan 2018 17:39:16 +0100
From:	"Bert Timmerman (bert DOT timmerman AT xs4all DOT nl) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] pin drill and thickness statistics from cvs.gedasymbols.org
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Reply-To:	geda-user AT delorie DOT com

karl AT aspodata DOT se wrote:
> Do theese thickness diameters look reasonable ?
>
>   all values in mm
>   c  = small/tight
>   b  = hopefully something normal
>   a  = something somewhat big
>   aa = big thickness
>
> 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
>    0.6   1.1   1.4   1.6   3.0
>    0.7   1.2   1.5   1.8   3.2
>    0.8   1.3   1.7   2.0   3.4
>    0.9   1.4   1.8   2.1   3.5
>    1.0   1.5   1.9   2.3   3.7
>    1.1   1.6   2.1   2.4   3.9
>    1.2   1.7   2.2   2.6   4.1
>    1.3   1.8   2.3   2.7   4.2
>    1.4   1.9   2.4   2.9   4.4
>    1.5   2.0   2.6   3.0   4.6
>    1.6   2.1   2.7   3.2   4.7
>    1.7   2.2   2.8   3.4   4.9
>    1.8   2.3   3.0   3.5   5.1
>    1.9   2.4   3.1   3.7   5.3
>    2.0   2.5   3.2   3.8   5.4
>    2.1   2.6   3.4   4.0   5.6
>    2.2   2.7   3.5   4.1   5.8
>    2.3   2.8   3.6   4.3   5.9
>    2.4   2.9   3.8   4.4   6.1
>    2.5   3.0   3.9   4.6   6.3
>    2.6   3.1   4.0   4.8   6.5
>    2.7   3.2   4.2   4.9   6.6
>    2.8   3.3   4.3   5.1   6.8
>    2.9   3.4   4.4   5.2   7.0
>    3.0   3.5   4.6   5.4   7.1
>    3.1   3.6   4.7   5.5   7.3
>    3.2   3.7   4.8   5.7   7.5
>    3.3   3.8   5.0   5.8   7.7
>
> each column is
>    thickness = a0 + a1 * hole_dia
>
>          a0      a1
> c:   0.2662  1.0966
> b:   0.6041  1.3211
> a:   2.0090  1.7107
> aa:  0.7195  1.5476
>
> I got theese by the procedure outlined in
>
>   http://aspodata.se/git/openhw/share/pcb/data_from_cvs.gedasymbols.org/readme.txt
>
> ///
>
> Loocking at https://www.samtec.com/support/pcb-hole-sizes I get much
> tighter values: 0.130 1.011
>
> ///
>
> Does IPC have any recommendation about this ?
>
> Regards,
> /Karl Hammar
>
> -----------------------------------------------------------------------
> Aspö Data
> Lilla Aspö 148
> S-742 94 Östhammar
> Sweden
> +46 173 140 57
>
Hi Karl,

What I do is:

- determine lead dimensions and shape (round, square, flat, etc.),

- determine required hole diameter and define in footprint file,

- 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 !

- 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.

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

- YMMV to the gallon ;-)


Kind regards,

Bert Timmerman.

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