Am building a table that utilizes 3/8"w x 4-1/2"lg x 3/4"dp mortises in the legs to receive tenons from the side rails.
Don't have a dedicated mortise machine and drill press attachments don't thrill me.
Do have a good 3/8" carbide forstner bit and a decent drill press, so that is the way it will be done.
Clamped a couple of rails to trap the work piece allowing it to slide parallel to the mortise centerline and went to work.
Completed the bulk of the stock removal with the forstner bit and faced the clean up of the side walls.
Someone skilled with a chisel would probably have used that technique, but chisel work, especially the amount involved, didn't thrill me.
Soooo.... enter the end mill.
Chucked up a 3/8", 4 flute, flat bottom end mill in the drill press, dropped it into the mortise at the correct depth, and pulled the work piece so the end mill cleaned up the sides of the mortise.
20 minutes later, the job was done.
As the saying goes, "different horses for different courses".
Lew