In manufacturing and mechanical engineering, flatness is the geometric condition in which every element of a surface, or of its derived median plane, lies in a single plane. It matters for workpieces and tools, and above all for precision parts that must mate across a surface in an air-tight or liquid-tight way, so such surfaces are normally machined or ground to a required degree of flatness and then checked by metrology. Flatness deviation can be defined as a least squares fit to a plane, sometimes called statistical flatness, or as a worst case, the distance between the two closest parallel planes that contain the surface, and it can be specified over a given area or an entire surface. Geometric dimensioning and tolerancing gives quantitative ways to state it, and ISO 12781-1 defines several measures, including the least squares reference plane, minimum zone reference planes, local flatness deviation and root-mean-square flatness deviation. Parts flat to about one helium light band can be wrung together, as gauge blocks are.
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Source Flatness (manufacturing) (Wikipedia)
In Field
Source Flatness (manufacturing) (Wikipedia)
Sources
1. Flatness (manufacturing) (Wikipedia)
History
Sir Joseph Whitworth popularized the first practical method of making accurate flat surfaces during the 1830s
In Field: Mechanical Engineering, Lead, first sentence
In manufacturing and mechanical engineering, flatness is an important geometric condition for workpieces and tools.
Associated With: Machining, Lead, fourth paragraph
Such surfaces are usually machined or ground to achieve the required degree of flatness.
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