GB726851A - Improved method of and apparatus for lapping articles - Google Patents

Abstract

726,851. Lapping. CRANE PACKING CO. April 10, 1953 [April 18, 1952], No. 9847/53. Class 60. A machine for lapping an article 38, such as a quartz crystal, includes a lap surface 11, a holder 12 to which the article is affixed for movement bodily therewith, means establishing relative movement between the holder and lap surface, and means to limit the movement of the holder toward the lap surface and comprising three limit stops 20 mounted on the holder and designed for ultimate contact with the lap surface. The surface 11 is covered with a lappping compound, such as an oil grit mixture, and rotated about a vertical axis while the holder 12 is held against circumferential movement by a cast-iron lap conditioning ring 13 freely rotatable about its own axis. Each stop-member 20 is provided with a diamond tip 35 and an inclined surface 29 to co-operate with a hardened ball 28 mounted at the lower end of a screw 26. The latter provides a coarse adjustment of the member 20 which may be rotated about its own axis by a pin engaged in one of a number of holes 23 for fine adjustment. The stop members are also provided with spring washers 24, locking screws 31 and rubber packing rings 32. The articles 38 are preferably placed within the triangular area defined by a series of straight lines passing through the effective points of the stops 20 and are secured to the member 12 by first applying a very slight amount of moisture to one or the other of the contacting surfaces. A ring of lacquer is formed around the article so that no grit or fluid can penetrate between it and the holder 12. As the stops 20 approach the surface 11 they produce visible tracks in the lapping compound which indicate that the lapping operation is approaching completion. The initial height of the stops 20 is determined by measuring instruments. Specification 652,655 is referred to.