In mechanical engineering, surface finish refers to the texture, primarily the roughness, of the surface of a machine. A good surface finish is important for many reasons. A smooth surface results in less friction, which reduces wear and tear. It also has a "cosmetic" effect. Modern consumers demand products that are highly uniform, sleek, and scratch-free. The quality of products they buy in the supermarket, in turn, depend on the quality of the machines that produce it. The surfaces of the machine components, such as gears, shafts, pistons, and bearings, therefore, are scrutinised to ensure that their roughness does not exceed the finishing standards.
Visually inspect the surfaces, and run your fingers along the edges of the surface to check for roughness. In processes that do not require extreme precision, a visual and tactile method may be sufficient.
Use a roughness gauge for higher precision. A roughness gauge works by tracing the surface you want to measure. In addition to roughness, it usually also records multiple other parameters such as waviness and form. Nowadays, you can buy hand-held roughness gauge, which makes checking for surface finish a breeze.
Compare the readings from the roughness gauge with the industry averages to determine whether your machine meets the required standards. Different machine processes (such as drilling, sawing, or flame cutting) yield different levels of roughness.