X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Message-ID: <4F9BFF5D.9010407@schinagl.nl> Date: Sat, 28 Apr 2012 16:31:57 +0200 From: Oliver Schinagl User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120416 Thunderbird/11.0.1 MIME-Version: 1.0 To: geda-user AT delorie DOT com Subject: [geda-user] Metric vs Imperial, Grid snapping Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: geda-user AT delorie DOT com Hi list, this time, somewhat unrelated question. Someone on this list posted a link to Tom Hausherr's blog about PCB design and that was an incredible interesting read. A few things he mentioned that where extremely interesting was his post about metric usage vs imperial usage of parts etc [1]. Here it is mentioned that metric is the way forward in PCB design and far it allows for far higher accuracy eventually. I'm sure hobby usage won't need/'allow' such high accuracy, most hobby PCB houses don't have equipment that does these high tolerances, but even so. Why is gEDA/PCB by default using the imperial system? It's quite easy to change, absolutely, but if it is actually recommended to use millimeters, why 'force' a default of mil's? Even if it is somewhat autodetected from the system's Language, mm should be the default, no? Also, he mentions using 0.05 mm routing grid as most component lead pin pitches are 0.05mm. My first design I used a grid size of 10mil's because that was the default. I used 8mil widths for nearly everything as seeed's minimal width is 6mil. 10mil was the closest for the grid. I guess the question is, what grid size would be recommended, depending on the fab house's tolerances? Oliver [1] http://blogs.mentor.com/tom-hausherr/blog/2011/03/31/inch-to-metric-conversion-tables-for-pcb-design/