Abstract: A grinding machine with a high production rate for pre-pointing drill bodies and the like in automatic duty cycles wherein separate grinding heads and a chuck head are respectively shiftable to and from a working position to grind both ends of the drill body simultaneously. The chuck head includes a special through-feeding rotary chuck which is journalled at its periphery and through which the work pieces are loaded and unloaded sequentially and unidirectionally by a fast-acting loading plunger advancing rapidly in an initial portion of its loading stroke, with completion at a slowed rate for accurate lodgement of the drill bodies with both ends precisely positioned for engagement by the grinding wheels.

Abstract: An automatic grinding machine adapted to cut and relieve spiral drill flutes and perform analogous form-relieving operations requiring helical advance of the work, wherein a linearly-moving carriage travels a rotary spindle and its work chuck relative to a grinding wheel in programmed duty cycles under control of logic circuitry with optional manual override control. Separate electric motors for the carriage and spindle are activated at adjustable speed ratios by digitally set binary drive pulses enabling instant change of helix angle or lead ratios and other working parameters by adjustment of digital switches at a simple control panel. A reversible tool head affords automatic cross-cutting capabilities; and a system of pulse-controlled indexing of the work is provided to increase the production rate of the machine by a method which effects the indexing as a function of the otherwise idle return travel of the carriage for restarting in successive work excursions.