One of the simplest lapping equipment uses a lap of ϕ200–ϕ300 mm. The workpieces are manually abraded against the lap at 300–1000 rpm while simultaneously supplying slurry and pressing the workpieces against the lap surface in a to-and-fro motion in the direction of the lap diameter. Such a lapping method is similar to the metallurgical polishing using Al2O3 or Cr2O3 abrasive powder and a felt sheet polisher; this polishing method is used to observe the microscopic structure of metal specimen.
Some improvements were made on lens lapping and polishing machines. For example, manual lapping operations were shifted to the machine, with increasing relative speeds between the work and laps while maintaining high working pressures. In a working operation of the lens and polishing machine, workpieces—with a driving pin at the center of the back—are forced against the rotation lap surface. The pin allows the workpiece to make reciprocating motions and to rotate in conformity with the revolution of the lap as shown inFigure 6.4.