Derby Worx Pro Wheel Mandrel for Pinewood Derby Cars Accurately machined shaft allows for precision use in any drill chuck or Dremel-type tool. Step-down on shaft allows BSA wheels to be mounted with the spokes facing the drill chuck, simplifying work on the inside edge of the tread. Knurled thumb screw eliminates the need to use a screwdriver to mount a wheel (a clumsy operation with the standard mandrel). Beveled thumb screw ensures that the wheel mounts accurately on the mandrel. Screw can be replaced should it be lost or bent.