Power feed rotary tool

A power feed rotary tool having a working head and an electric motor with an output shaft for rotating the working head, a pneumatic system for feeding the working head towards a workpiece, an elongate housing with the working head at one end thereof, a drive train within the housing for rotating the working head, a piston within the housing for feeding the working head as it rotates towards the workpiece, a control rod at the other end of the housing, means for restraining said control rod from rotating with respect to said housing and connecting said control rod to the drive train so that said control rod is fed together with the working head, the control rod including an abutment for limiting the feeding of the working head, means for drivingly connecting said electric motor to said drive train between the ends of said housing comprising a toothed drive belt, a toothed driving pulley on the motor output shaft and a toothed driven pulley in the drive train, and drive belt being operatively connected to said pulleys, and a device for tensioning said drive belt comprising an adjustable motor mount for mounting said motor on said housing, means on said device for engaging said housing to retain said device in fixed position relative to said housing means, including a threaded member on said device for engaging said adjustable motor mount, said threaded member being rotatable to move said drivingly pulley away from said driven pulley, a compression spring operatively associated with said threaded member, and means for preventing rotation of the threaded member when a predetermined degree of compression of the spring has been reached to provide the correct tension in said drive belt.