GB888980A - Improvements in or relating to saw chains - Google Patents

Abstract

888,980. Making chains. SANDVIKENS JERNVERKS A.B. June 15, 1960 [June 16, 1959; Feb. 4, 1960], No. 21104/60. Class 83 (2). [Also in Group XXV] In a method of making links for a saw chain the ends of the rivet holes in the links are workhardened by cold-coining. The chain comprises cutting links 4, driving links 6 and interconnecting links 8, and the ends of the rivet holes in each of the links is coined by pressing with a pair of steel balls 18, 20. The depth of the countersink is between 8-25%, and preferably between 10-15% of the link thickness. A tangent to the mid-point of the curved surface should make an angle with the axis of the hole between 40 degrees and 55 degrees, preferably 45 degrees. The diameter of the balls should be 50% to 200% greater than the diameter of the hole. Fig. 8 shows a press tool comprising an upper die unit 52 and a lower die unit 54 which is mounted in a plate 64 supported by a heavy spring 68. The link is located over the ball dies 60, 62 by a plate 67. In a modification (not shown, see Fig. 9) the balls are replaced by spherical ended cylindrical plungers. In a further modification the plungers have frustoconical ends and in a third modification the surfaces 98 (Fig. 5) are made convex by forming them with a cylindrical die of the same diameter as the hole and which has a concave protruding flange around the base part. Details are given of a typical link, the pressure used on the dies and the results of tests on the links produced.