I am looking to engrave some ABS plastic electronics enclosures and need some guidance on a suitable bit to use. I am just looking to label the various cutouts on the enclosures, probably with about 3/16" high lettering. I have a Zenbot with a RotoZip router as my spindle.
For engraving soft materials like plastics with 1/8" to 1/4" high letters you probably want to use a 1/8" x 2" engraving cutter with a 50 or 60 degree included angle and a 0.010" or 0.015" tip. The ones that I use are from Bits and Bits located in Silverton Oregon which is fairly close to me and provides quick service. Take a look at: Engraving Cutters and engraving bits