GB574245A - Improvements in or relating to saw tooth surface broach - Google Patents

Abstract

574,245. Broaching saw teeth. LAPOINTE MACHINE TOOL CO., Ltd. (Lapointe Machine Tool Co.). Jan. 20, 1944, No. 1130. [Classes 83 (ii) and 83 (iii)] In a method of making saw teeth, the stack is broached simultaneously with two sets of alternately-disposed cutting units having cutting teeth a, b spaced at double the linear pitch of the saw teeth c to be produced, with the cutting teeth of one set staggered one half-tooth space relative to the teeth of the other set, so that the front and rear faces of each saw tooth are formed by the action of the two sets of cutting units whereby a series. of completed saw teeth of the desired pitch is produced on each operative stroke of the broach. A number of strips of saw stock are clamped together and cut simultaneously. The broach comprises a base member 20 adapted to be secured to the ram of a surface - type broaching - machine to which member is keyed a plate 21 with upstanding side flanges 25, 26 adapted to receive clamping bars 33, 34 for securing the various elements of the broach which are carried on the plate 21 between the flanges 25, 26. The final element is a pilot block 27 comprising a steel block having its ends formed at an angle of approximately 7 degrees so that the block is at an angle to the front end of the broach. Behind the pilot block are shearing units 28, each with clamping lugs 47 and a cutting edge 48. In addition to the 7 degrees cut at the ends, each unit is cut away at 3 degrees on the bottom so as to provide clearance for the top surface behind the cutting edge 48. Six or eight shearing units are provided, progressively increasing in height by 0.001" per unit. The tooth cutting units 30, 31 are generally similar to the shearing units with cut-away ends and bottom faces and formed with cutting teeth disposed at twice the pitch of the teeth c to be cut in the work s. The teeth of the units 30 are staggered with respect to the alternate units 31 and the lines of intersection of the two sets of teeth together form the saw teeth c as shown in Fig. 19. The teeth 50 are rounded both at the roots and at the points and are cut at an angle of 5 degrees, as shown in Fig. 10, so that the end angle of 7 degrees provides a slight clearance at the cutting faces. The broach assembly is completed by a backing block 40.