Lapping
Lapping is a machining process in which two surfaces rubbed together with an abrasive between them, by hand movement or by machine. This can take two forms. The first type of lapping traditionally called grinding, involves rubbing a brittle material such as glass surface, such as iron or glass itself also known as "lap" or grinding tool with an abrasive such as aluminum oxide, jewelers Rouge optics, emery, silicon carbide, diamond, etc., between them. This produces microscopic conchoidal fractures as the abrasive rolls between the two surfaces and removes material from both. Another form of lapping involves a softer material such as pitch or a ceramic for the lap, which is "charged" with the abrasive. The lap is then used for cutting hard material of the workpiece. The abrasive is embedded in soft material that keeps him and allows him to score and cut the harder material. Taken at the thin limit, this will lead to a polished surface such as a polishing cloth on a car or a polishing cloth or polishing the resin on the glass or steel. Taken to the limit, with the aid of accurate interferometry and specialized polishing machines and skilled hand polishing, lensmakers can produce surfaces that are flat to better than 30 Nm. This is one twentieth of the wavelength of light from the commonly used 632.8 Nm helium-neon laser light source. Surfaces this flat can be linked to molecular optical contact, combining them under the right conditions. This is not the same as the wringing effect of Johansson blocks, although it is similar.