Surface Roughness

Quick Answer

A surface roughness gage (also called a profilometer or surface finish tester) is a precision instrument that measures the microscopic texture of a machined or finished surface — quantifying parameters such as Ra (average roughness), Rz (mean roughness depth), and Rmax to verify that a part meets its specified surface finish requirements. Surface roughness measurement is critical in applications where fit, friction, sealing, fatigue life, or coating adhesion depends on surface texture.