Accuracy and Surface Roughness
Lapping can be used to obtain a specific surface roughness; it is also used to obtain very accurate surfaces, usually very flat surfaces. Surface roughness and surface flatness are two quite different concepts. Unfortunately, they are concepts that are often confused by the novice.
A typical range of surface roughness that can be obtained without resorting to special equipment would fall in the range of 1 to 30 Ra (average roughness in micrometers or microinches).
Surface accuracy or flatness is usually measured in Helium Light Bands, one HLB measuring about 0.000011 inches (280 nm). Again, without resort to special equipment accuracies of 1 to 3 HLB are typical. Though flatness is the most common goal of lapping, the process is also used to obtain other configurations such as a concave or convex surface.
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Famous quotes containing the words accuracy and/or surface:
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