After drilling a 5/16" hole in a piece of wood, I use this drill bit to widen the hole at the bottom so I can have a 1/4"-20 -Can use T-bolts to make my woodworking jigs and jigs adjustable. With this cutter (and a 5/16" straight cutter) I can cut a T-slot. No more ordering a T-track and waiting for it to arrive. Also, it's a lot cheaper to make your own. Next on my list is to buy a larger t-slot bit so I can use carriage bolts in that track.