# Parallelism Vs. Flatness

Parallelism and flatness are two terms in measurement that contribute to the accuracy of your precision instrument. Especially when working with a micrometer, the flatness of the flat anvil must have a good condition. Besides, when dealing with gauge blocks, the gauge blocks’ flatness and parallelism determine their grade.

But what are actually parallelism and flatness? These two words seem to be similar to hear. But they are actually different.

The easiest way to understand parallelism is by having two lines that never meet no each other matter how far they extend. They will never meet at a point. While the flatness is one of the lines. As long as it extends without bending; totally straight, it’s flatness.

Now then, imagine if the line is a plane. If the two surfaces of a plane never meet no matter how broad it is, it’s parallelism. While the flatness is one of the surfaces of the plane. As long as it expands without neither concave nor convex part, it’s flatness.

For professional use, the reliability of a precision instrument cannot be separated from parallelism and flatness. Therefore, during the calibration, we have to check out both the measuring faces to see whether there is an issue with parallelism and flatness or not.

There are several ways to check parallelism and flatness. But, one of the possible ways to measure parallelism and flatness of the micrometer is by means of an optical flat. The optical flat is the tool that its surfaces are very flat. And if we compare the two surfaces, they are very parallel. During the use, there will be some lines of color that appear. You have to be a little bit educated to do that.

You can also use the block gauge but this measurement is qualitative. It means no value generated, only the sense of whether it’s flat or not.