Improvements in or relating to grinding machines

1,082,368. Grinding. HOY CARBIDES Ltd. Dec. 16, 1965 [Dec. 16, 1964], No. 51224/64. Heading B3D. A machine for grinding the teeth of cutters, such as trepanning cutters 12, comprises a rotatable holder 13 for a cutter, a grinding- wheel 10, means for automatically reciprocating the work-holder and grinding-wheel with respect to one another so that the cutter is alternately clear of the grinding-wheel and sufficiently close thereto that a cutter tooth engages the grinding-wheel, and means for automatically indexing the work-holder when the cutter is clear of the grinding-wheel so that another cutter tooth is engaged when the cutter is next close to the grinding-wheel. The holder 13 is mounted at the upper end of a pillar 14 and has a lever 40 for operating an eccentric to clamp the cutter 12 in the holder. The pillar is mounted on a V-slide 16 which is adjustable on a further V-slide 19 by means of a lead screw to position the cutter relative to the diamond grinding-wheel which may be of the shallow dish-type driven by an electric motor 11. The slide 19 is connected to the rod 22, Fig. 2, of a pneumatic cylinder 21 controlled by a pair of valves 24, 25 actuated by fingers 26, 27 on the slide, the slide thereby being automatically reciprocated to move the cutter clear and adjacent the grinding-wheel. A ratchet wheel 15 is secured to the holder 13 and each time the slide is moved to a position wherein the cutter is clear of the grinding-wheel, the ratchet wheel, and hence the holder 13 and cutter 12, are rotated a distance sufficient to position the cutter for the next tooth to be ground by a pawl 29 which is mounted on a post 28 on the lath 20 and extends through a slot in a guide post 30 mounted on the slide 16, a spring in the post 30 urging the pawl upwardly against a roller at the upper end of the post. Rotation of the holder during grinding is prevented by a finger 31.