Rob, I didn't have the skills or desire to build a CNC router from scratch. I bought this one on Ebay with controller for $1800 US.
It normally has a Bosch Roto-Zip router head on it, but they claimed a Dremel tool would engrave. They are horrible. What one needs after a CNC router is procured, is a professional belt-driven engraving spindle and associated bits.
After mounting the spindle on the router, a small ac or dc motor and pulley is needed to drive the belt. The spindle is 1" and the pulley is 3" so my "turns ratio" is to step-up spindle rpm. 5000-10000 rpm is good. I use a dc motor from an old 3/4" sony vcr, and it's old reel hub became an excellent pulley!.
I vary the dc from a supply to vary rpm.
I should probably stop and say that once you get a router, you should check it to see if its tolerances will allow for the precision of engraving.
Clamp a fine ballpoint pen in the router and run some text and draw on some paper on the router bed. If the lines have no chatter and are straight, your engraving will be too.
Ok, back to engraving.. this is a spindle from a Dahlgren Wizzard engraver I bought for $200 US. It is the key to a fine job. It suspends the bit between two fine bearings 4 inches apart for minimum play and runout. They can be found from various manufacturers. Various tip sizes of the dropin bits range from .005 to .025 etc depending on line width desired. Hope this has helped. Larry
