On Thu, Oct 13, 2016 at 1:56 PM, Brent Hilpert <hilp...@cs.ubc.ca> wrote: > As Tony suggests, it matches up with 5/32" spacing, just as 0.125 is 1/8". > Where the rounding of the 1/4 thou (0.00025) took place - in the name or the > implementation - I'm not sure.
Implementation. Years ago I verified with several vendors that the connectors really were engineered for 0.156" or 3.96mm, not 5/32" or 3.97mm. (I'm not 100% certain that was always true, but it was when I inquired.) It doesn't make much difference in practice. The highest pin-count .156" connector I've ever dealt with was 86 pin (43x2), and the difference in the nominal first-to-last position is only 10.5 mils, which is on the order of the non-cumulative position tolerance. I just happened to look at the drawing for a TE 2-530666-1 connector, and they specified the pitch in one place as 0.156/3.96 (in/mm), and in another place in the same drawing as 0.156/3.175. Oops!