Patent GB-835816-A (GB)
Title: Method and apparatus for lapping
IPC: B24B37/10
Filed: 1957-09-23
Abstract: 835,816. Lapping. CRANE PACKING CO. Sept. 23, 1957 [Sept. 24, 1956], No. 29865/57. Class 60. A method of lapping a surface on an article while simultaneously dressing a lap surface comprises forming a lap plate with oppositely directed lamp surfaces, rotating the lap plate about an axis passing through both surfaces, applying the article to one side of the lap plate and a dressing tool to the other side thereof and utilizing the rotation of the lap plate to establish relative motion between the same and the article and dressing tool respectively, and repeatedly inverting and rotating the lap plate so that the article and dressing tool are alternately and successively applied to the opposite sides of the lap plate. The face of a bolting flange 52 of an aircraft engine cylinder assembly 50 is lapped by the upper face of a lap plate 44 on which lapping compound is spread, the part 55 of the cylinder beyond the flange being received in a central bore 60 in the plate. The lower face of the lap plate 44 rests on, and is trued by, the annular lap surface 20 of a lap plate 18 rotating about a vertical axis and projecting through an opening in the table top 12. One of the bolt holes 54 in the flange 52 is engaged by a pin 82 on the end of a rod 72 vertically slidable on and rotatable about a stud 75 projecting upwardly from a standard 74 mounted on a plate 36 secured to the table top 12, the rod 72 is normally pressed by a spring 78, adjustable by nut 80, against spacers 76 on the stud 75, but can be raised to withdraw the pin 82 from the bolt hole 54 whereupon the rod 72 can be pivoted clear of the lap plate 44. The lap plate 44 is located by antifriction rollers 42 engaging its cylindrical surface and carried by a yoke 30 adjustably secured by bolt 34 to the plate 36. The lap plate 44 has secured thereto centrally of its thickness a ring gear 57 meshing with a hub gear 68 secured on the drive shaft 66 of the lap plate 18, the teeth on the gears are so shaped as to permit various degrees of mesh, dependent on the adjusted position of the lap plate 44. The lap plate 18 is trued by a conditioning ring 26 similarly located by rollers 42 on an adjustable yoke 30 but rotated only by the lap plate 18. Abrading compound is fed from a storage and agitator tank assembly 90 through an aperture controlled by a solenoid-actuated valve 92 on to a wire 94 bearing against the ring 26. The lap plates 18, 44 have grooves 100. During a lapping cycle, the lap plate 44 is turned upside down, so that the face trued by lap plate 18 becomes operative and the other face which has been operative is trued by lap plate 18, the reversal being repeated as often as necessary. If the bore 60 in the lap plate 44 is so large that the lap plate approximates in shape to the conditioning ring 26, the latter may be omitted. In a modification, Fig. 5, the lap plate 144 has its periphery relieved on both sides at 101, and is provided with holes 103 corresponding with the bolt holes 54 in the flange 52 to prevent the accumulation of lapping compound in the bolt holes. Specifications 652,655, 672,527 and 676,284 are referred to.