Grinding machine and method of sharpening grass mower bedknives

A portable grinder for grinding the bedknife of a grass mowing machine which grinder comprises a guide rail with opposite ends, a grinding wheel assembly for receiving a rotary grinding wheel which assembly is mounted for movement to and fro along said guide rail, readily releasable attachment members for releasably securing the grinder on the mowing machine such that when said grinding wheel assembly is moved along said guide rail the grinding wheel can move along a blade face of said bedknife and grind it, wherein said grinding wheel assembly includes deflector means for automatically deflecting rotary blades of said mowing machine out of the path of movement of said grinding wheel in both directions of movement relative to said guide rail during movement of said assembly, first adjustment means being provided to adjust the position of said guide rail adjacent its opposite ends relative to said bedknife and second adjustment means being provided to adjust said grinding wheel assembly relative to said guide rail and hence relative to said blade face of said bedknife in a direction perpendicular to that of the guide rail.