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.
Read more about this topic: Lapping
Famous quotes containing the words accuracy and/or surface:
“As for farming, I am convinced that my genius dates from an older era than the agricultural. I would at least strike my spade into the earth with such careless freedom but accuracy as the woodpecker his bill into a tree.”
—Henry David Thoreau (1817–1862)
“The surface of the earth is soft and impressible by the feet of men; and so with the paths which the mind travels. How worn and dusty, then, must be the highways of the world, how deep the ruts of tradition and conformity!”
—Henry David Thoreau (1817–1862)