Is it true that lapping 2 mating surfaces allows for a positive seal?

Lapping two mating surfaces is indeed a process that can lead to a positive seal. This technique involves grinding and polishing the surfaces to create a very flat and smooth finish, which helps to eliminate any irregularities between the mating parts. The purpose of lapping is to ensure that the surfaces come into close contact with each other, allowing for a tighter fit when assembled. This close contact minimizes gaps where fluids could leak, resulting in a more effective seal.

The improvement in the surface finish from lapping not only enhances the sealing capability but also increases the overall performance and lifespan of the components involved. It is particularly beneficial in applications where precision is crucial, such as in valves or fittings where prevention of leaks is essential.