Patent GB-821703-A (GB)
Title: Improvements in or relating to lapping machines
IPC: B24B37/27
Filed: 1956-08-14
Abstract: 821,703. Lapping. CRANE PACKING CO. Aug. 14,1956, No. 24841/56. Class 60. A machine for lapping a face on an article includes a lap surface movable relative to an article holder, the article holder comprising a body portion and a leg portion carried by the body portion and movable relative thereto about a horizontal axis, the article being secured to the holder for application to the lap surface of the machine with the weight of the holder bearing upon the article, a limit stop member mounted on the free end of the led portion and designed for ultimate contact with the lap surface to limit the extent of lapping operation on the article and means for adjusting the angular position of the leg portion relative to the body portion. A lapping machine has a circular lap plate 14 rotating about a vertical axis, the annular lap surface 16 having a lapping compound applied thereto and being continuously dressed by a conditioning ring 18 within which is loosely positioned an article holder 10. This comprises a steel block with outwardly extending arms 24. Articles A, e.g. quartz crystals, are wrung to the under surface of the holder. The block has three vertical bores 28 each communicating with a vertical split 30 which forms opposed clamping arms 32, 32 drawn together by clamping screws 34 to secure a supporting rod 40. The lower end of each rod 40 has a diamond rest 44 with a frusto-spherical surface 46. Each arm 24 of the block has an inclined slot 50 communicating with a horizontal bore 52 which intersects the vertical bore 28 ; a leg 54 is thus formed and fine adjustment of the diamond rest 44 is effected by an adjusting screw 56 passing through an opening 58 in one arm 32 and having its shank threaded into the main body of the block. In operation, each diamond rest 44 is adjusted to the same distance from the under surface of the block 22, so determining a plane parallel to that surface. One or more articles are secured to the surface so as to lie within the triangle bounded by the diamond rests and the block placed within the conditioning ring ; the lap plate reduces the thickness of the articles until the diamond rests 44 move into contact with the lap surface 16, which state is indicated by visible tracks on the lap surface. The articles are then reversed for lapping on their opposite faces. A modified holder for use in lapping optical prisms, such as binocular prisms, or gauge blocks comprises, Fig. 4, a block 60 having laterally projecting portions 64, 66, 68, and an inclined surface 70 to receive thereagainst one face of an article to be lapped. In a further modification, Fig. 6, curved slots 50<SP>1</SP> extend downwardly from the upper face of the block 62<SP>1</SP>. In a still further modification, Fig. 9, the adjusting screw 56a is threadedly received through the leg portion 54a with its end bearing against the remote side of the slot 50a. The various holders may have a central bore 20 or 20<SP>1</SP> in the upper surface for reception of a pin to restrain the holder against revolution about the axis of the lap Specification 726,851 is referred to.