Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.
This can take two forms. The first type of lapping (traditionally called grinding), involves rubbing a brittle material such as glass against a surface such as iron or glass itself (also known as the "lap" or grinding tool) with an abrasive such as aluminum oxide, jeweller's rouge, optician's rouge, emery, silicon carbide, diamond, etc., between them. This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both.
The other 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 to cut a harder material — the workpiece. The abrasive embeds within the softer material, which holds it and permits it to score across and cut the harder material. Taken to a finer limit, this will produce a polished surface such as with a polishing cloth on an automobile, or a polishing cloth or polishing pitch upon glass or steel.
Taken to the ultimate limit, with the aid of accurate interferometry and specialized polishing machines or skilled hand polishing, lensmakers can produce surfaces that are flat to better than 30 nanometers. 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 molecularly bonded (optically contacted) by bringing them together under the right conditions. (This is not the same as the wringing effect of Johansson blocks, although it is similar).

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  1. Kruel J

    Ring lapping

    In case some haven't seen it done..... Here is a one piece Burris PEPR mount that was professionally lapped by the techs at Vortex. Lapping involves using a known true straight tube and abrasives to ensure the rings/mount are truly straight and the scope is evenly supported by said mount. Even...
  2. Aero Denezol

    Is scope ring lapping necessary? Opinions?

    Is scope ring lapping recommended for any/all scopes, or is this primarily reserved for high-end optics and 1000 yard rifles? Is it worth the trouble for a 100 yard plinker? Is it possible to lap anodized aluminum rings without ruining them? Your thoughts are greatly appreciated,
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