Having spent a previous life as a die maker, I know that drills like to find a low spot to center themselves on. When machinists need a hole in a precise location they use a smaller, very stout drill to make a starter hole. I concur that a (15 thou.???) starter hole for hand-drilled PCBs will aid in ctc accuracy. There is probably a way to compute from drill diameter, copper thickness and lead angle exactly the best diameter starter hole for a particular diameter of drill. Say the diameter of hole that allows the drill to contact copper before the substrate by a few mils?
Phil Taylor _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
