GB601758A - Method of finishing gears - Google Patents

Abstract

601,758. Gear-cutting. FELLOWS GEAR SHAPER CO. Oct. 11, 1945, No. 26547. Convention date, Feb. 8. [Class 83 (iii)] In a method of finishing previously cut gears, a workpiece and a pinion type cutter having cutting edges at one end only are rotated in mesh at a relatively high speed and given a relative axial reciprocation at a slow speed so that the cutting action is a drawing cut largely in the direction of the root to crest and crest to root of the gear teeth. A differential between the rotations and the timing of the reciprocations is introduced to give an axial feeding effect such that successive strokes are distributed over the entire face area of the gear teeth. For example, when the cutter and gear have an equal number of teeth, the cutter may make eight reciprocations during seven rotations of the work and each cutting stroke then takes place during <SP>7</SP>/ 16 of one rotation of the work. The cutting stroke of cutter tooth t begins at point 15 on the tip of tooth A and a cut is taken from the adjacent faces of teeth A and D by the leading and trailing edges respectively of tooth t. The following cutter teeth cut in the following gear tooth spaces until the return stroke begins, for which the cutter and gear are relatively moved apart. The second cutting stroke begins when the work has turned through # of a revolution and the gear tooth B and cutter tooth t<SP>1</SP> have moved to the dotted positions B<SP>1</SP> and t<SP>11</SP>, the cutting action beginning at point 16. The cutting action may be brought nearer the root to crest direction without reducing the ratio of reciprocations to rotations by shortening the strokes to less than the full axial width of the gear and repeating the cutting cycle with corresponding shifting of the locus of reciprocations. The cutter and gear may have a different number of teeth ; for example, with seven teeth on the cutter and six on the gear, the cutter may make one reciprocation during one rotation while the gear makes 1 <SP>1</SP>/ 16 rotations. The feeding effect may also be obtained, with or without imparting a differential, by beginning and ending successive strokes at different points along the path of reciprocating movement. For finishing helical gears, the axes of the cutter and gear may be relatively inclined or a helical cutter may be used and rotated with a speed differential between its cutting and return strokes sufficient to compensate for the increment of angular movement necessitated by the helix.