GB1368942A - Lapping devices - Google Patents

Abstract

1368942 Lapping SIEMENS AG 8 Aug 1973 [8 Aug 1972] 37578/73 Heading B3D A device for lapping a magnetic head to have a slight convexity in the form of a circular cylinder comprises a lapping plate 1 which, when in operation, has a concave surface in the form of a section of a cylinder, is rectangular and, when in an unstressed condition, is flat, the rear face of the plate having, except in the vicinity of its ends, a plurality of ribs 4 running parallel to the ends and spaced equidistantly from one another. The lapping plate is provided with a fixture into which it can be inserted and which is adapted to exert upon respective zones of the plate adjoining the ends variable opposite moments which are identical in magnitude. The lapping plate is rectangular and of metal and the ribs 4 cover the rear face except near the ends 2, 3 when shoulders 5, 6 having elongated holes 7, 8 are provided. The fixture consists of a pair of jaws 9, 10 mounted by pivot pins 11, 12 in a common bearing block (not shown) and connected by a bar 13, the length of which is variable by a screw 14 to pivot the jaws about the pins 11, 12. The lapping plate rests on knife edges 15, 16 on the jaws and the shoulders 5, 6 are received in recesses formed in the jaws so that pins can be engaged with holes 17, 18 formed in the jaws and the elongated holes 7, 8. When the length of the bar 13 is increased, the jaws pivot about the pins 11, 12 so that the knife edges 15, 16 and the pins engaging the holes 7, 8, 17, 18 exert force couples on the ends of the plate which is thereby deflected to have a concave shape. In other embodiments, the shoulders are formed with short legs engaging further knife edges on the jaws. The surface of the plate may be formed with crossed grooves 30 which are connected to a source of vacuum and over which is a perforated sheet 31 and a lapping foil 32.