Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Milling circuit boards works best with carbide bits. The best bit
is the 60 degree milling bit. GCode must be offset correctly or your
traces will be too thin and the pads will be too small. The
outlines_gcode.ulp has a place to adjust your offset. The "V" bit
allows for variations in PCBoard thickness. With good HOME switches
you can send the machine back out and have the machine mill the board
deeper a second time.

Feedrate is .0004" to .0006 for each revolution of the bit. So
if the Dremel is set to 3-1/2 around 12,000 RPMs your feedrate would
be 6" per minute (.0005 X 12,000RPMs) These number come from Think &
Tinker A very involved circuit on a 4" X 6" board will take an hour
and 20 minutes if the GCode has been optmized.