I used a piece of 1/2" 1018 cold rolled. Drilled and tapped one end for the 1/4-20 thumb screw, drilled the other end 23/64' and pressed in a 3/8" bearing ball.
Thanks! I'll have to make myself one. I like simple tools with just a touch of "flair". Classy
Just go a little at a time on each side. Keep everything straight. When you try and get one side perfect and the other is way off it will be hell to get it straight again.
For the measuring tool I use a stick of welding rod.