I purchased a diamond drag engraving tool with the idea of engraving a logo into the blades I make for my planes and other tools.  This tool does not rotate like a router bit.  As the name implies, it is simply dragged across the surface of the part.  Rather than use the router collet to hold the tool, I made an aluminum holder that bolts to the router mount on my machine.  Router bearings tend to have some play in them so that they don't overheat at high speed.  This creates some back-and-forth movement that I didn't want with this tool.

My first attempt at engraving met with mixed results.