Mobius wrote:Spring loaded diamond drag bit is what I'd use.
Agree. I tried to engrave stainless with a flat tip engraving spade bit a couple of times with and without lubricant. Kind of worked but it always looked a bit messy.
The diamond drag bit is much cleaner and faster. However, the lines are extremely fine and e.g. larger text would need something like a pocketing tool path to get a hashed interior.
Here some of my diamond drag experiments on stainless (the golden one is also stainless with some plating):
I used a homemade sping loaded drag bit holder with a 1/4" linear ball bearing (inside the big tube). Held in the non-rotating spindle and works quite well.