Abstract: A grinding machine for sharpening toothed saws includes a saw blade holder for rotatably holding a saw. A pneumatic or hydraulic ram drives a cam back and forth in one of a number of preselected grooves in a rotatable cam plate for driving a pawl in an arcuate path for rotating the saw blade. Each saw tooth is thus advanced, one tooth at a time, through a grinding position in which a rotating grindstone sharpens the face or top of the saw tooth. The position of the grinder head arm is adjustable through an arc of about 105.degree. to permit top and face grinding without turning over the grindstone or the spindle arm on which the grindstone is mounted. The head arm is tiltably mounted on a heavy plate and releasably secured to the periphery of the plate for stability.

Abstract: An automatic dual side grinder is disclosed. A circular saw blade is supported and rotated in angular increments for grinding of each saw tooth. A pair of radially-opposed, parallel grinding wheels are reciprocated, by a crank assembly radially of the blade to grind opposite sides of each tooth. The crank assembly is driven continuously by a DC electric motor. An electric control circuit for the motor has two subcircuits, each including a resistor which determines motor speed. Control is switched between the subcircuits synchronously with reciprocation by a switch actuated by a rotating cam on the crank assembly. The resistors are preferably variable rheostats. Different rheostat settings are used to grind a saw tooth at one speed and retract the grinder at a second, higher speed.