PURPOSE: In an automatic edge grinder for a lawn mower, to grind the edge automatically and accurately by fastening the edge on a splitting disc through a bolt and simply operating the handle back and fro.

CONSTITUTION: The edge 13 is mounted on a splitting wheel disc 12 then a washer plate 14 is mounted and a fastening screw 15 is applied, thereafter the base 6 is fine adjusted and moved by means of a handle 17 to set the edge position against the grinder 16 and the screw 15 is fastened to fix the edge 13. Thereafter the grinder 16 is rotated to advance the handle 3 in arc while grinding the edge 13 and when the handle 3 is stopped by the adjusting screw 8 the grinding work is stopped at the setting depth. consequently even when the handle 3 is returned, the nail tooth 11 is engaged with one stopping notch 9 to collide the splitting disc 12 and the edge 13 against said position thereby only the handle body can be returned to the original position. Then the handle is advanced again to repeat the operation thus to complete the grinding of the edge.