a tool having a rigid support. The ring connections should first be checked and resoldered if necessary, and tne ring examined carefully to make sure that it is tight on the shaft. It is generally preferred to remove the rotor from the machine and place it in a lathe, as this offers the best accessibility and more rigid support for turning, although the rings aay be turned with the rotor left intact within the machine. The choice between the two methods depends largely on the size of the machine, Before starting to turn or grind the rings, the windings of the rotor should be carefully protected from metal chips by wrapping them with canvas or some other closely woven material. This serves to shield the windings from any chips or metal dust which are certain to result in short circuits, When turning or grinding the rings extreme caution must be taken to give the cutting tool 32 rigid support. It is best to take a light cut, taking several if necessary, to remove all bad spots on the rings. fine grain sandpaper or commutator stone may be used for final surfacing, with care taken to eliminate all scratcnes; especially those running diagonal on the ring surface, until the rings have a highly polished surface, after the rings have been carefully inspected the surface should be lightly polished with fine sandpaper or commutator stone. Windings should be thoroughly blown out, and all copper dust wiped from the slip ring surface and adjacent parts. A close watch on all electrical equipment with periodic servicing will give years of dependable and uninterrupted performance. A little 3-40