GB925970A - Improvements in or relating to the manufacture of knife blades - Google Patents

Abstract

925,970. Making knife blades; bending; forging. MASSEY-FERGUSON S.A. Sept. 7 1959 [Sept. 5, 1958 ; July 11, 1959], Nos. 28554/58 and 23890/59. Classes 83 (2) and 83 (4). A method of making knife blades for agricultural machines comprises perforating a strip along lines defining the ultimate cutting edges of the blades, performing a blade processing operation on the edges and then making other perforations to merge with the first and so part the blades from the strip. A strip 11, Fig. 3, is advanced step-by-step while successive punching operations are performed. The first trims the edges of a portion and forms the oblique slot 16 shown in full lines and forms positioning holes 13, 15. The second trims a further portion and removes the parts shown in dotted lines while the third removes the parts shown in dot-dash lines. The areas shown by cross-hatching are those removed later to part the blades S from the strip. Before separating the blades, the strip is pressed between a die 21, Fig. 5 and a matrix 30, Fig. 9, which bend downwardly and form teeth in the edges of the slots 16. The strip is then ground along the plane X-X, Fig. 8, to produce a bevelled serrated cutting edge E. The die 21 comprises two ridges 22 arranged in V-formation and each having inclined grooved faces 23 with triangular facets 25, 26 at each end. The matrix 30 has channels 31, 32 conforming to the slots 16 in the strip and flanked by downwardly-inclined grooved faces 33. Three pins 36 co-operate with locating holes 15 in the strip. In order to minimize lateral flow of metal the grooves 24 of the die alternate with those 34 of the matrix, Fig. 11A, and all the grooves are wider and deeper adjacent the cutting edges of the blades and merge to form points along the outer sides of the inclined faces. Also, the die teeth are asymmetrical and the matrix and die are slightly offset so as to increase the difference between the distances T and t until the resultant reactions R1, R2 of the metal on the dies bisects the apex angles of the grooves. In one modification, the blades are formed without teeth and in another, teeth are formed on one side only and the edges are not bent, the cutting edge being formed by grinding along the line A-A, Fig. 23, after separating the blades from the strip.