GB164047A - Improvements in milling cutters - Google Patents

Abstract

164,047. Marks, E. C. R., (Pratt & R Whitney Co.). Dec. 3, 1919. Milling - cutters; backing-off lathes.-A backedoff milling-cutter for cutting contours, parts of which are considerably inclined to the axis of the cutter, has longitudinally-inclined teeth, the cutting edge being so formed that its projection about the axis upon an axial plane gives a curve identical with the contour to be cut. The teeth overlap and may be radially faced or undercut. The front face of each tooth is preferably a helicoid and the backing-off curve at any cross-section a spiral, so, that an effectively unaltered cutting face may be obtained by grinding each tooth to a new face parallel to the original face. Figs. 1 and 2 show a cutter B with radially-faced teeth, and Fig. 18 shows diagrammatically a machine for making such a cutter, by means of a fine-pointed tool S which travels a distance less than its width for each complete revolution of the blank D, being guided by a former W. To produce the backing- off curve the tool S is reciprocated through a distance r, Fig. 9, for each tooth on the blank, by a cam 45 driven by worm gearing 51 and bevel gearing 52 from a shaft 48 and operating a slide 40 carried on the main cross-slide 39. As the tool S travels to the left, the alteration in phase of the reciprocation, necessitated owing to the inclination of the teeth to the axis of the blank is produced by means of a cam-slot connection 60 between the driving sleeve 56 and the mandrel 55, under the control of an arm 58 attached to the carriage 38. In the case of undercut teeth, a retarding of the backing-off action is provided for by arranging the bevel-wheel 52 to slide on its shaft in unison with the main slide 39 and to be driven by the shaft 50 through longitudinal cam slots (not shown).