Just like the wheel bore, the axle surface must be smooth to support a monomolecular film of graphite. The axle need not be perfectly round, as only a line on the bottom side is in contact with the bore. It is best to mount the axle nail in the chuck of an electric drill that has been clamped to a table with C-clamps or fixed stationary in a vise. The polishing compound is a special blend of non-fibrous alundum powders that will bring the zinc coating on the axle nail shafts to a high polish. The square birch dowels are used to press the polishing powder against the axle. The dowels are soft enough to conform slightly to the axle roundness and porous enough to hold the polishing powder.