GB1215443A - Improvements in or relating to piercing punches - Google Patents

Abstract

1,215,443. Punching. REDMAN ENG. Ltd. 2 Feb., 1968 [8 Nov., 1966], No. 49957/66. Heading B3W. A piercing punch, particularly for piercing sheet metal, comprises a head, a nose, a shank in two relatively axially adjustable parts, adjustable or interchangeable spacing means for holding the parts in their selected relative axial positions whereby the effective length of the punch may be varied and means for holding the two parts of the shank together. As shown, Fig. 1, an upper shank part 2 carries a head 4 and lower shank part 5 is integral with a nose 7. A selected one, 14, of several spacers of varying lengths is located in blind bores 10, 11 in the end faces of the shank parts and a draw nut 18 secures the shank parts together. Alternatively the spacers may be balls of different diameters and two interengaging draw nuts may be used. In another embodiment (Fig. 3, not shown) a threaded spigot (61) on the upper shank part is screwed into a threaded bore (62) in the other part with a shim (66) of selected thickness clamped between the parts. The nose (82) of a further embodiment (Fig. 4, not shown) is formed separately from the shank and is a sliding fit in a bore (84) in the lower shank part (81), the underside of a flange (83) at the upper end of the nose abutting the upper end of a threaded spigot (80) forming part of the lower shank part. The spigot is screwed into a threaded bore (75) in the upper shank part to an extent determined by the thickness of a shim (85), surrounding the spigot. A bolt (77) engaged in a threaded bore (74) in the upper shank part is screwed down on to the flange (83) to hold the nose in place. In a still further embodiment, Fig. 5, the lower shank part 91 is formed with two series of recesses, one of each series being shown at 95, 96. Each series comprises recesses of different depths, each recess in one series having a complementary recess of the same depth in the other series. Two projections 101 on the upper shank part 87 are inserted in whichever pair of recesses gives the desired shank length. A draw nut 102 holds the parts together. Any of these punches can be used with a stripper such as that shown in Fig. 1 in which a stripper 25 surrounding the punch is biased upwardly by a spring 31 acting between a flange 29 on the stripper and a fixed stripper plate 30. A stronger, stripper spring 28 acts between the head 4 of the puncher and the flange 29. The variable shank length enables the working blows of the punches in a bank of punches to be staggered.