Belt drive for machine for resurfacing vehicle brake discs

Apparatus for automatically driving a brake disc refinishing tool for refinishing vehicle brake discs while said discs are on said vehicle, and said vehicle has caliper mounting brackets, said apparatus comprising, a frame having means detachably connectable to the caliper mounting brackets adjacent to a brake disc, a tool carriage movably mounted on said frame and carrying a pair of tools engageable with opposite faces of said brake disc, a lead screw rotatably mounted on said frame and threadedly received in said carriage to drive said carriage upon rotation of said screw, means mounted on said screw to manually rotate said screw to position said carriage relative to said brake disc, a first pulley fixedly mounted on said lead screw, a motor having a power output shaft, means pivotally mounting said motor on said frame, a second pulley fixedly mounted on said output shaft of said motor, a belt trained around said first and second pulleys for transmitting power from said motor to said screw, spring means for biasing said motor away from said frame so as to tighten said belt, and releasable locking means for locking said motor to said frame in a position where said belt is loose.