Lapping

Lapping is performed by using lap and abrasive powder. Abrasive

powders like emery, corundum, aluminium oxide etc. are rubbed

against the surfaces of job with the help of a lap made of soft

materials like brass, copper, lead, soft cast iron, soft steel etc.

Lapping is performed manually or by machine. The figure illustrates

the method of lapping the face of small blocks in a vertical axis

lapping machine.

Lapping remove very thin layer of metal (0.005 to 0.1 mm). It is performed to correct minor surface imperfections, improve  dimensional accuracy or to maintain fit between two mating parts. It is considered as a low efficiency process in surface finishing operations.