Bridge Pin Hole Slot Saw
It's another easy-to-make tool
Here's a really simple and useful tool.
Get the skinny Bosch jig saw blade and epoxy it into any kind of simple handle.
Here, I've just used a scrap of mahogany and Sears Craftsman #928843 Sabre saw blades (or Bosch #101AO)
These things have razor sharp coarse teeth that cut on the pull stroke. It's a breeze to make the string slots in bridge pin holes with this saw. The blade is just about the right size for the first 3 strings, and can be used with a "rocking, rolling motion" to accommodate the thicker bass strings.
For me, these blades work much better than the little utility saws commonly sold for slotting bridge pin holes.