[jfong]

Someone asked for some more detail about the spring loaded diamond drag that I made.

Short piece of 1/2 drill rod that bored out on the lathe a little less than 1/4". Used a reamer to fit the 1/4" drill rod so it slides smoothly. Drill and tapped a hole at one end for a spring stop. Drill a 1/8" hole for diamond tip at the other end. Use a set screw to lock the diamond tip in.