GB718184A - Improvements in or relating to lapping machines - Google Patents

Abstract

718,184. Lapping. NATIONAL RESEARCH & DEVELOPMENT CORPORATION. June 19, 1952, [June 28, 1951.] No. 15397/51. Class 60. In a lapping machine comprising upper and lower lap elements between which a thin sheet is disposed as a work holder for work pieces positioned for engagement by the opposing surfaces of the lap elements, the upper lap element is mounted so as to be capable of a combined slight horizontal and vertical movement while operating on the work pieces. A machine particularly for lapping quartz crystal plates for high frequency oscillators comprises a lower lap plate or ring 2, Fig. 2, secured, e.g. by screws, to a base 5; an upper lap plate or ring 1 rests on work pieces 6 supported in a circularly arranged series of apertures in a work holder comprising a thin circular disc 7 disposed horizontally between the lap plates 1, 2. The disc 7 has a central boss 8 in which is mounted a pin 9 secured to an eccentric disc 10 on a driving shaft 11 extending vertically through a central aperture 3 in the upper lap plate 1. The upper lap plate 1 is disposed with play in a central aperture 14 of a stationary annular plate 15 supported by pillars from the base 5. During operation the upper lap plate 1 slowly rolls round the inner periphery 14 of the restraining plate 15 under the drag action of the work pieces 6, thus allowing the upper lap plate a high degree of freedom to float on the work pieces. In a modification, a fixed restraining disc 17 Fig. 4 is disposed with play in the central circular aperture 3 of the upper lap plate 1. The disc 17 is supported from a beam 18 mounted by pillars 19 on the base 5; the shaft 11 extends through a central aperture 20 and the lower lap plate 2 and through the base 5. In both embodiments, the upper lap plate 1 is preferably provided with one or more apertures through which abrasive material is supplied to the lap faces; a suspension of fine abrasive powder in oil or water may be used.