If it divides roughly, fixed and free (loose) abrasives are used for processing. Processing with the free abrasives includes buffing and abrasive shot machining in addition to lapping and polishing. Lapping and polishing are, however, considered two of the most outstanding processing methods achieved by causing sliding frictional forces between the work surface and the tool. Slurry is constantly fed into the tool during this process.
The main difference between lapping and polishing processes is obvious in glass lens manufacturing. Lapping produces a rough surface processed with coarse abrasives and a hard plate tool, while polishing produces a mirror-like surface processed with fine particles abrasives and soft pads. Table 6.1 shows the difference among processing conditions and the mechanisms between the lapping and polishing.