Vlakheids

Vlakheids, in Dutch, refers to the property of a surface to be flat or to lie in a single plane. In everyday use it often appears in technical and manufacturing contexts as a tolerance: how much a real, manufactured surface deviates from a perfect plane. Vlakheid is distinguished from other surface characteristics such as roughness, which describes microscopic texture rather than overall form.

In mathematics and geometry, vlakheid is related to planarity. A set of points is planar if they all lie on one plane in three-dimensional space. A plane is a flat, two‑dimensional surface that extends indefinitely. The mathematical description of a plane can be written as ax + by + cz + d = 0, where a, b, c define the plane’s orientation and d its position.

In engineering and metrology, vlakheid is used to specify and verify the flatness of objects such as metal sheets, machined parts, and optical surfaces. The flatness of a surface is typically defined as the maximum distance between the actual surface and a reference plane. Practical measurement methods include coordinate measuring machines (CMM), height gauges, optical flats, and surface plates. The result is often expressed as a tolerance range, indicating acceptable deviations for functional assembly and performance.

Vlakheid interacts with related ideas such as form, straightness, parallelism, and location within geometric tolerancing (GD&T). It is a fundamental quality attribute in manufacturing, quality control, and engineering design, enabling parts to fit and function reliably in assemblies.