This is set up in a drill press. You can regulate the depth by adjusting the depth gage. This is a box cuter set into a piece of 2x4 material. A table saw blade made the kerf cut and the box cutter fits very snug. I use this for 10 ga. 2 7/8", 12 ga. 2 1/2", 16 ga. 2 9/16" and 20 ga. 2 1/2". Each dowel is snug on the inside of the hull and I have it marked on each dowel how far it had to be on for the correct cut.
If you don't have a drill press, dis-regard, but now a days you can buy them very cheap.
These happen to be 20 ga.
