We carry out lapping, which involves two materials with an abrasive in between gliding against each other in other to remove fine-grained particle from one or both of the materials depending on the type used.
In type A lapping, the two materials are getting lapped at the same time i.e. fine grained particles of both of them are removed simultaneously. This type A requires two hard materials, one brittle and one hard and an abrasive staying in their middle while they rub against each other, the abrasive thereby grinds the both surfaces at the same time.
In type B lapping, one of the materials is soft and the other is hard, this textural difference produces a smoothening or polishing finish of the hard material. The abrasive charges the soft material, allowing it to hold against the harder one.