Simple CNC Engraving Head

My very first summer job was working at the local trophy shop, where we had several computerized engravers.  As it turns out, they were extremely similar to the Taig CNC mill that I would many years later acquire – driven by steppers in the X and Y axes and controlled via a desktop PC, it’s really not a stretch to consider them specialized CNC tools.  Our most commonly used engraver was a ‘diamond drag’ type, which essentially used a diamond tipped tool to scratch through the lacquer covering a sheet of brass or aluminum (our other engraver used a rotary cutter for engraving on plastics).

Once I had my Taig, I realized I could certainly do a little engraving myself, I just needed the right tool.  On the engraver at the trophy shop, the ‘head’ was actually pneumatic – rather than a Z axis, there was simply a 3-way solenoid valve that would apply air to a spring retracted engraver.  More air pressure meant deeper engraving.  There had been plans in Home Shop Machinist (might have been the sister publication, Machinist’s Workshop) for a spring-loaded engraver for use on CNC mills a while back, but I wasn’t thrilled with the design – not only did it reduce the working travel in Z, but had to go in the spindle.  I wanted an engraver that could be attached to the side of the headstock (Taig headstocks have T-slots for such purposes) which would not only be a bit more rigid, but would allow me to machine a shallow flat on a part and immediately engrave in that area without any tool changes.

Construction is simple – the only purchased parts were the diamond drag engraver (I used a DG-250 from Antares), a pair of clamp collars, and a spring. The body was a hunk of scrap extrusion from work – it had a 5/16″ hole already down the length of it. I machined a pair of bushings from some Oilite bronze rod stock and pressed them into each end of the body (I had bored each end out a little bit). Though I had reamed the bushings to have a 1/4″ hole through them, there was enough axial misalignment between the two to cause the engraver to bind when I tried to run it through. So I tried something a little crazy – I chucked a long piece of 1/4″ drill rod in the lathe, lightly scuffed the last two inches or so of the rod with a diamond hone, slathered it in oil, and ran it through the bushings. This trued things up just enough to allow the engraver to slide through the bushings freely, but with zero side play. A bit of strip steel, some threaded rod and wingnuts, and it’s ready to attach.