Power drawbolt with planetary drive

Power drawbolts which are rotatably mounted within a machine tool spindle and are rotated by an electric motor to screw into a threaded opening in a toolholder to secure the toolholder within a socket on the front end of the spindle. First and second spur gears (44, 46) ara formed on the rear end of a spindle (10) and drawbolt (24), respectively. The gears (44, 46) are positioned side by side and are equal in diameter, but have a differing number of teeth. A planetary gear cage (52) surrounds the spur gears (44, 46) and has pinion gears (54) which mesh with both of the spur gears (44, 48). The planetary gear cage (52) is attached to the armature of an electric motor (58) which, when energized, rotates the gear cage (52) and thus causes the drawbolt (24) to rotate at a reduced speed. The speed reduction depends on the differonce in the number of teeth in the two spur gears (44, 46). Preferably the motor armature (66) is axially shiftable to move a locking ring (78) on the planetary gear cage (52) into and out of engagement with the spur gear (44) on the spindle (10).