I stumbled across this diamond drag engraving bit when I was looking for some other cutters for my CNC. This bit allows you to engrave hard materials like stone, steel, and glass, or soft materials like plastic, aluminum, and brass. You can even score glass for cutting.
The special bit measures 3-3/4″ long and doesn’t spin like a regular bit. It chucks into a 1/4″ collet and is designed to be dragged across your work material by the CNC – kind of how you would use a manual scriber.
Yes, that’s correct – your spindle must be OFF when you use this drag engraving bit.
The diamond tip is spring-loaded, to apply constant pressure on the material. Since it is spring-loaded, the bit can compensate for a waste board or materials that aren’t perfectly flat. As it is dragged, the bit will engrave a line approximately 0.005″ wide.
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When you buy the bit, you get the spring-loaded holder, high and low pressure engraving springs, the 120° diamond tip, a hex wrench for replacing the tip, and detailed instructions on how to set up your CNC. You can also purchase a 90° tip separately, which is recommended for engraving coated materials.
The bit will run you $180 at Widget Works Unlimited and the cheapest shipping method listed was about $9. There’s also a 1/2″ shank version for the same price.
If you are curious about seeing a bit like this in use, check out this video from Jim McPherson. He’s using a similar diamond drag bit to engrave a name on a knife handle. Skip ahead to about 2 minutes if you just want to see the bit in action.