Here are a few pictures. Believe I used a #10 cap head socket screw that I bought locally to make sure I had the correct tap. It's on a 1/2" bar as I didn't have any 3/4" rod laying around. Think I made this about 14" long.
It works well, but I also don't worry about trying to get the inside finish smooth (other than what you can feel or see). It has come in handy for finishing in and around the shoulder area which isn't always easy to reach with the hook cutter.
Saw he released a negative rake cutter, may pick one up just to have it, although I often use the standard cutter at an angle for a shear cut for better surface. Negative rake would work well for problem/grabby areas, but much slower in removal.