fladens

Fladens is a term used in metrology and engineering to describe the degree to which a surface approximates a mathematically perfect plane. The concept is applied to specify and assess how flat a surface is within a defined reference frame, and it is distinct from related properties such as surface roughness or straightness.

In technical terms, flatness is defined as the greatest distance between any point on the surface and a plane that fits within the surface boundary. This differs from straightness, which concerns a single line, and from roughness, which describes micro-scale texture. Flatness is typically discussed at the level of a component face or a set of datum features and is reported as a tolerance value over a specified gauge length or area.

Measurement methods include optical interferometry, profilometry, and coordinate measuring machines (CMMs). The measurement process involves aligning the workpiece to a reference frame, selecting a datum or reference plane, and recording deviations across the surface. Results are commonly expressed in units such as micrometers and are used to verify compliance with design tolerances.

Applications are found in precision manufacturing, optics, stamping, and automotive and aerospace engineering, where planar accuracy affects assembly fit, sealing, and performance. Strict flatness tolerances help ensure proper function and reliability of interfaces between components.

Standards and practice vary by region, with flatness specifications appearing in general geometric tolerancing guidelines and industry-specific standards. Terminology may differ; in some Scandinavian technical literature, fladens is used as a calque of the English term flatness, while native terms such as planhet may also be used.

See also: planarity, surface roughness, straightness.