Hi Mahmood,

You want the panel symetrical about the pins in order to maximize the usable area of the panel. But you might do multiple boards on a single panel. Those boards, as Per points out, do not need to be symetrical about the line between the registration pins. All that matters is that your CNC system "knows" where those pins are.

Typically this is done by defining them as a cartesian axis. For example, if both pins are at locations where x = 0, they are on the y-axis. But in practice they could be at any line x = r, as long as the CNC system knows what r equals. Then, when you flip the board, any point on your board that was at x = r + q will now be at x = r - q (which should make plain why r = 0 is a convenient choice), and any point that was at y = p will still be at y = p. In summation, if your pins are both at x = 0 (the y-axis), a point on your board (q, p) will be found at (-q, p) after it's flipped.

Of course, this will also work if you define the line between the pins as the x-axis, only now it will be the y-coordinate that becomes negative when the board is flipped, and the x-coordinate will remain unchanged.

I strongly discourage you against trying a diagnal transform.

The only other thing I can tell you is that I use 3 mm holes in my panel and 2.95 mm registration pins.

If you are familiar with the CP2102 (USB/UART bridge chip), that is the smallest footprint I can do reliably with my standard bit. It has 28 pads, 7 per side, with a 28th ground pad in one corner and a large ground pad in the middle, all inside a 5 mm x 5 mm square. And yes, it took a few attempts to get it right.

Good luck,

Joe