Descriptions:

The measurement of Surface roughness Comparator is not as straightforward as most other engineering measurements, such as length or angle or hardness; and in order to get good accuracy, expensive instruments are needed. These are often unsuitable for workshop use, where roughness of machined surfaces can usually be assessed conveniently and with sufficient reliability using visual and tactile (fingernail) comparison with a standard set of surfaces machined in the same way. This set consists of 30 comparison specimens, covering six commonly-used machining methods (6 turned, 6 end-milled, 6 horizontally milled, 6 surface-ground, 3 lapped, 3 reamed/drilled.