Split Mandrel 3091 Split mandrels hold emery paper, allowing you to use either a polishing machine or Flex-shaft machine to sand the inside of objects such as rings, tubes, bushings, etc. The split mandrel 3091 is made of metal, is straight 2" in length, and has a 3/32" shank. It is to be used with a flex shaft machine. Diameter where paper is attached is 2.35mm (3/32"). Mandrel is not tapered.