The Martindale chain-drive commutator grinder is a departure from previous designs, in that friction has been reduced to a minimum. Grinding dust has little effect on the operation.Two or three turns of the crank will mover the carriage from one end of the bed to the other. The operator can feel the stone cut, and how fast to feed it. This is probably the quickest and easiest commutator grinder to use. NEEDS 1 SUPPORT TO OPERATE. Supports not included. Use of commstones with dimensions of 1x1-1/2x6-1/2 or 1x2x8 is recommended.