Abstract: In a grinding machine for relief grinding the blades of a lawn mower blade cylinder having a rotatable drive shaft (14) on which a grinding wheel (20) is mounted for rotation therewith and for axial movement therealong, a grinding wheel guide assembly (30,34,42) to traverse the grinding wheel axially of the drive shaft and means (46) for causing the traverse of the guide assembly alternately in opposite directions so that the grinding wheel reciprocates along the drive shaft during rotation thereof, a blade guide assembly (53) comprising a guide finger (54) axially slidable along a fixed guide shaft (57) mounted parallel to the drive shaft, a guide element (58) engageable with that face of a blade to be ground which is remote from the grinding wheel and connecting means (60,62) coupling the guide finger to the traverse means and locking means (66) to releasably engage the grinding wheel guide assembly and the blade guide assembly with the traverse means.