GB664315A - Improvements in or relating to surface type broach with multiple inserted cutters - Google Patents

Abstract

664,315. Broaches. LAPOINTE MACHINE TOOL CO., Ltd. (Lapointe Machine Tool Co.). Sept. 14, 1949, No. 23758/49. Class 83 (iii). A broach, particularly for forming blade grooves in a turbine rotor, comprises a body 20 having a longitudinal channel 21 in which a number of separate cutters are held by clamping bars 54 having convex surfaces 56 engaging notches 51 in the sides of the cutters. Each bar has a flange 55 along the outer edge and the inner edge is either convex along its whole lower length or is bevelled with convex projections 56 so that, on tightening screws 57, the bar rocks slightly into engagement with the lower surfaces of the notches 51. The cutters comprise a set of roughing cutters 31, a set of cutters 32 for chamfering the mouth of the groove, a set of finishing cutters 33 and a cutter 34 for finishing the bottom of the groove, the latter being adjustable for depth of cut by a shim 62; the cutters are preceded by a pilot member 30. The pilot member and the cutter 34 bear against fixed abutments 35 and 85 at each end and locking blocks 40, of which the forward one has a projection 44 for supporting the tops of the roughing cutters, are fitted behind each set of cutters. Each locking block has a tapered recess 41 engaged by a screwadjusted wedge 42 and is secured in the adjusted position by screws passing through elongated slots 5. The cutters 31 and 33 are cut away at the rear to provide chip clearance, leaving a narrow web 71, Fig. 9, which bears against a strip 77 inserted into a slot 76 in the concave face of a succeeding cutter; the strips are held frictionally or by pins 78.