On Wed, 27 May 2015, gareth wrote:

I wonder if anyone here has experience of milling PCBs using
CNC rather than etching them, and if so, what pitfalls and pratfalls
were encountered?

No, but I have done boards at times using a Dremel tool and a cutting bit.
It worked better for discrete components than ICs, it being easier to
make larger "pads", and I'm not certain
just building over the circuit board is all that worse. You have to use a
light touch, press too hard and maybe you cut through the board, don't
press hard enough and you may not isolate the "pad" enough.

Obviously if you have a CNC, you can do much finer work. I don't really
see why subtracting via cutting is all that different from subtracting via
etching, though if making multiple boards, you make the layout and can
etch the boards at the same time, while with a CNC, you have to do one at
a time.

Michael