Air Engraver
This project is a follow-on to the dog-tag project. It came about because the current tags were nearing the end of their lifespan. Buddy's, in particular, looked like it had been run over by a freight train. Instead of redoing the existing design, which would have been straightforward, I wanted to create a true engraving device. The original approach cuts at around 8,000 RPM, which is dangerously slow for expensive, brittle carbide engraving bits, but this is the practical maximum rotational cutting speed for my mill. The result is that the linear cutting speed has to be unbearably slow, so a tag takes probably an hour to engrave per side. I decided to build an add-on to the mill headstock for an external air drill that operates at around 56,000 RPM.
The engraver is an inexpensive air drill. It has very little runout, so the accuracy is great.
A convenient piece of Delrin to hold it. Unfortunately, it's not shaped the way I need.
So I had to face cut it and square it off on all sides.
Delrin is silky smooth and vacuums up wonderfully.
This is boring the rough hole, which is intentionally a couple thousandths of an inch too narrow.
An adjustable chucking reamer in the drill press (not shown) took care of the difference to make for snug fit. I originally had planned to give it a set screw, but it didn't turn out to be necessary.
Here's rounding over the corners for cosmetic reasons only.
On the back are two square nuts that slide into the T-slots on the headstock of the mill.
All mounted up.
The controls for the general-purpose air supply, which runs the engraver and misting system on the mill, as well as a bunch of other stuff. The remote project describes this further.
And here the engraver is in action, creating new dog tags. (Coming soon)