![]() Variations of this symbol provide additional instructions as described in the table below. ![]() The basic surface finish symbol is a checkmark with the point resting on the surface to be specified. Roughness is the most commonly specified, measured, and calculated aspect of surface finish, and many people use the term “Surface Finish” to only describe roughness. Surface roughness, frequently shortened to roughness, refers to small irregularities in surface geometry. Waviness requirements are less common than roughness requirements, but they can be important for certain parts, such as bearing races or sealing surfaces. Waviness spacing (Wsm) is the peak-to-peak spacing of the waves, while the wave height is defined by the average waviness (Wa) or total waviness (Wt) parameters. The waviness profile does not include any irregularities in the surface due to roughness, flatness, or form variations. Waviness is measured over an evaluation length, and a waviness profile for that length is generated. These periodic imperfections in the surface are larger than the roughness sampling length but small, short, and regular enough that they are not considered flatness defects.Ĭommon causes of surface waviness include warping from heating and cooling and machining defects from chatter or deflection. Waviness is the term used for the most broadly spaced surface finish variations. We will discuss the symbols and interpretation of lay in the Symbols section below. Lay is generally produced by the manufacturing process and can be parallel, perpendicular, circular, crosshatched, radial, multi-directional, or isotropic (non-directional). ![]() Lay is the term used to describe the dominant pattern on a surface and the orientation of that pattern. This diagram gives an idea of how to think of the relationship of Waviness, Lay, and Roughness: Another term, analogous to Surface Texture, is Surface Topology. Surface Finish when it is intended to include all three characteristics is often called Surface Texture to avoid confusion since machinists often refer to Surface Roughness as Surface Finish. Surface Finish is a measure of the overall texture of a surface that is characterized by the lay, surface roughness, and waviness of the surface. The latter process may be grinding (abrasive cutting), polishing, lapping, abrasive blasting, honing, electrical discharge machining (EDM), milling, lithography, industrial etching/chemical milling, laser texturing, or other processes Definition of Surface Finish ![]() If necessary, an additional process will be added to modify the initial texture. The process is usually optimized to ensure that the resulting texture is usable. Sometimes, stick-slip friction phenomena can be observed during sliding, depending on surface texture.Įach manufacturing process produces a surface texture. Surface textures can be isotropic or anisotropic. Considerable efforts have been made to study the influence of surface texture on friction and wear during sliding conditions. Surface texture is one of the important factors that control friction and transfer layer formation during sliding. It comprises the small, local deviations of a surface from the perfectly flat ideal (a true plane). Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness.
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