Square Holes for Square Pegs
Rough cut the mortise with a hollow-mortise chisel for clean results
I like to build Craftsman-era furniture and my pieces usually include square pegs. To cut square holes for these pegs, I bought extra 1/4-in. and 3/8-in. hollow-chisel mortising bits and I honed them razor sharp.
To cut a square hole, I place the bit where the peg will be inserted and give it a few whacks with a mallet. I then remove the waste with a chisel and glue the square peg in place. Then I bevel the edges of the peg with a chisel.
Drawing by Jim Richey.