Split Mandrel 308 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 308 is made of metal, is straight 2 1/4" in length, and has a 3/32" shank. It is to be used with a flex shaft machine. Diameter where paper is attached is 5mm (3/16"). Supplied by the dozen.