What at is the best bit or setup for engraving AR15 serial numbers? We’ve been using our laser.
IME (as an 07/02 that used to do it a lot), keep using the laser, assuming a galvo fiber. They are much easier to set up and much more versatile, especially if you’re marking somebody else’s parts. Even a spring-loaded engraving bit doesn’t make perfect marks on un-level surfaces and getting the surface level unless you just machined it can be a PITA.
If you are machining the surface to be engraved, you can use a single flute engraving bit and spin it at max speed. A flatter tip or a U will last longer at the expense of line width. Be sure to clean off any burrs before checking depth as ATF doesn’t count burrs.
Diamond-drag takes a lot of passes to get to a reasonable depth.
Fiber laser is your best solution. Trying to debur customers finished coated parts leads to lawsuits. If the parts aren’t finished you can make a go. You will probably want to mill a flat spot first then engrave the number. Either way check out Xebec for deburing. They are a bit tricky to get right the first time but amazing once you dial it in.