A grinder apparatus for grinding the backside of the blades of a reel mower for cutting grass, the grinding apparatus comprising: means for applying controlled torque to the reel mower and its cutting blades; a rotatable grindstone; means for rotating the grindstone; a carriage for supporting the grindstone and moving the grindstone on a traverse from right to left or vice versa along the blade on the mower to allow the grindstone to sharpen the back side of each successive blade; a rest for holding a said blade of the reel mower in a position against the grindstone for grinding the back side of the blade; means for releasing the grindstone from the blade allowing the reel mower to rotate to the next blade, which in turn a relief grind is ground into the back side of the next blade, and successively ground into all of the other blades on the reel; means for limiting the traverse of the grindstone during the relief grinding operation on both the right and left ends of each blade of the reel; sensing means to determine the position of the grindstone relative to the right and left ends of the reel; and means to transmit information from the sensing means to means for stopping the traverse of the grindstone beyond set limits at both the right and left end of each successive blade, characterised in that an electric actuator is connected to a plunger in contact with the rest, the electric actuator being configured to pull the plunger away from the rest to allow the reel to rotate to advance the next blade towards the grinding position, and the electric actuator being in contact with the sensing means to ensure the grinding of the relief angle in the blade to each end of the blade. means for applying controlled torque to the reel mower and its cutting blades; a rotatable grindstone; means for rotating the grindstone; a carriage for supporting the grindstone and moving the grindstone on a traverse from right to left or vice versa along the blade on the mower to allow the grindstone to sharpen the back side of each successive blade; a rest for holding a said blade of the reel mower in a position against the grindstone for grinding the back side of the blade; means for releasing the grindstone from the blade allowing the reel mower to rotate to the next blade, which in turn a relief grind is ground into the back side of the next blade, and successively ground into all of the other blades on the reel; means for limiting the traverse of the grindstone during the relief grinding operation on both the right and left ends of each blade of the reel; sensing means to determine the position of the grindstone relative to the right and left ends of the reel; and means to transmit information from the sensing means to means for stopping the traverse of the grindstone beyond set limits at both the right and left end of each successive blade, characterised in that an electric actuator is connected to a plunger in contact with the rest, the electric actuator being configured to pull the plunger away from the rest to allow the reel to rotate to advance the next blade towards the grinding position, and the electric actuator being in contact with the sensing means to ensure the grinding of the relief angle in the blade to each end of the blade.