GB680848A - Improvements in magnetic workholders - Google Patents

Abstract

680,848. Magnetic work-holders. HITCHCOCK, S. I. July 12, 1951 [July 12, 1950], No. 17483/50. Class 60. [Also in Group XXXV] A magnetic work-holder comprises a block built up of laminations 1, Fig. 2, of magnetic material separated by laminations 2 of non- magnetic material, the block being divided into halves in a vertical plane at right angles to the laminations by non-magnetic material 5, Fig. 1, so as to form two pole-pieces to co-operate with a diametrically magnetised permanent magnet 7 mounted for angular movement between operative and inoperative positions. The laminations 1, 2 may be of soft iron and aluminium respectively. They are secured together by bolts 3, which may be non-magnetic, and tapped inserts 4. The two pole-pieces are connected by bolts 6 of aluminium or other non-magnetic material. The magnet 7, which may be built up from laminations formed from a hard magnetic alloy, is provided with a bore lined for half its length with white metal 13 which is extended into the other half of the bore by splines on a shaft 9 when the latter is driven into the magnet. This shaft is mounted in bearing bushes 10 supported by non-magnetic end caps 11 and carries a lever 14 which co-operates with fixed stops to determine the operative and inoperative positions of the magnet. The poles of the latter are formed as two arcuate faces which when positioned opposite the pole-pieces provide flux paths E through the work-piece C and through the surface supporting the block. The underside of the block is cut away at 16 to restrict the flow of flux into the supporting surface. Rotation of the magnet through 90 degrees to the inoperative position produces the flux paths D. To hold flat work-pieces an auxiliary work-holding surface (not shown) is provided. This also consists of alternate laminations of non-magnetic and magnetic material arranged to form a flat surface and adapted to bridge the sloping faces of the block with its laminations perpendicularto those of the latter. The block may have its faces case-hardened and accurately machined to enable it to be used for marking off. A pillar.(not shown) adapted to screw into one face of the block may be used to carry a dial gauge, scriber or other instrument. Specifications 576,710 and 578,075 are referred to.