Some online shops selling CNC router bits only specify what metals the bit can be used on. Is it safe to assume that if the bit can be used to mill metals that it's safe to use all types of non-treated wood?
Specifically, I'd like to mill douglas fir, but also interested in walnut.
I can't imagine a bit capable of milling metal having any difficulty whatsoever dealing with fir or walnut.
However I don't know you can assume that a metal-cutting bit will leave a particularly good surface on wood because of the different edge geometry (similar to twist drills, where metal-specific ones are subtly different to general-purpose or wood-specific ones). So it's probably a good idea to expect that a very light skimming cut will be needed to finish off.
I agree with Graphus, however also be careful of the max. RPM of the tools, since metal-cutting tools are often designed to run more slowly than woodworking tools.
Our engineers sometimes do this, usually testing the stability of the spindle and the fuselage, but not too long, and the original drill bit can be used for very thin aluminum panels. For environments where the voltage is not stable enough, the use of metal-specific drill bits is very dangerous. The coil of the motor controls the power, and the difference is still very large. If you don't use it often, you can buy a voltage stabilizer (not a voltage regulator), or you can use it occasionally.
Milling cutters can be used to cut wood.
Milling cutters and router bits have different geometry that recognizes much higher SFM used for wood and plastic. A milling cutter can, of course, be run at high SFM in wood.
One thing to be cautious of is chip removal. If you are edge milling it is not an issue, but if you milling a pocket then you could get sawdust buildup in the pocket that could jam or overheat the cutter.
