I engrave mainly on wood, glass and crystal using a 400,000 RPM high speed engraver. (a modified dental drill) My average cutting tool bit is .002″ in diameter.
I also use diamond and carbide hand tools for engraving fine details.
My one policy regarding engraving is that I do not engrave guns and weaponry. I do not choose to beautify objects whose designed purpose is to kill and maim humans and animals.