.svg)
Surface Roughness (Ra)
A measure of the texture of a machined or finished surface, expressed as the arithmetic average deviation of surface height from the mean plane. Ra values are called out on engineering drawings for surfaces with specific functional or cosmetic requirements.
Surface roughness (Ra) is a measure of the arithmetic average deviation of surface height from the mean plane, expressed in microinches (µin) or micrometers (µm), and is specified on engineering drawings when surfaces have specific functional or cosmetic requirements. Finely machined or hand-finished surfaces might specify Ra 0.8 to 1.6 µm for smooth, low-friction operation, while rough-finished surfaces from grinding or blasting measure Ra 3.2 to 12.8 µm or higher.
Surface roughness directly impacts coating adhesion, paint flow, appearance, and part functionality; rough surfaces provide better mechanical interlocking for coatings but may be undesirable for sliding surfaces that benefit from smoothness. Process capability for achieving target roughness requires understanding the inherent limitations of each finishing method, grinding, polishing, and tumbling can each achieve specific ranges.
Specifying realistic surface roughness targets prevents expensive rework and ensures your fabrication meets both functional and aesthetic requirements.
Price Your Project
Receive a free, custom quote for you project. Midwest Metal Fabrications can handle any job, small or large and is ISO 9001:2015 and AS9100 Certified.