Which metal is NOT suitable for lapping?

Explanation:

Lapping:

• It is an abrading process for refining surface finish and the geometrical accuracy of flat cylindrical and spherical surfaces
• It is a process or removing surface roughness, tool marks, surface cracks from grinding, slight distortions and other minor – defects from previous operations
• Lapping produces geometrically true surfaces, corrects minor surface imperfections, improves dimensional accuracy and provides a very close fit between two contact surfaces

The following parameters have an effect on the lapping process.

1. Abrasives type
   • B₄C is used for lapping dies and gauges. It is more expensive than SiC and Al₂O₃
   • SiC is intended for rapid stock removal. It is mainly used for lapping hardened steels, CI, and non-ferrous metals.
   • Al₂O₃ is intended for improved finish. It is used for lapping soft steels.
2. Grit size and abrasive grading: Grit size generally ranges from 50 to 3800, however, more generally, grit size from 100 to 1000 is used depending on the degree of surface finish required.
3. Vehicle: This prevents scoring of the lapped surfaces and varies from clean water to the heavy grease.

Important Points

Diamond is used for lapping tungsten carbide and it is a very precious stone but among the options, Copper, Lead, and Brass frequently used, so option 2 is suitable to answer.