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In manufacturing and mechanical engineering, flatness is an important geometric condition for workpieces and tools. Flatness is the condition of a surface or derived median plane having all elements in one plane. [1] Geometric dimensioning and tolerancing has provided geometrically defined, quantitative ways of defining flatness operationally.
In this process, three approximately flat surfaces are progressively refined to precise flatness by manually rubbing them against each other in pairs with colouring matter in between, and then hand-scraping the high points. Any errors of flatness are removed by this scraping, since the only stable, mutually conjugate surface shape is a plane.
The three-point bending flexural test provides values for the modulus of elasticity in bending, flexural stress, flexural strain and the flexural stress–strain response of the material. This test is performed on a universal testing machine (tensile testing machine or tensile tester) with a three-point or four-point bend fixture.
In the past, surface finish was usually analyzed by hand. The roughness trace would be plotted on graph paper, and an experienced machinist decided what data to ignore and where to place the mean line. Today, the measured data is stored on a computer, and analyzed using methods from signal analysis and statistics. [3]
Engineer's blue is prepared by mixing Prussian blue with a non-drying oily material (for example, grease).The coloured oil is rubbed onto a reference surface, and the workpiece is then rubbed against the coloured reference; the transfer (by contact) of the pigment indicates the position of high spots on the workpiece or conversely highlight low points. [1]
A straightedge or straight edge is a tool used for drawing straight lines, or checking their straightness. If it has equally spaced markings along its length, it is usually called a ruler. Straightedges are used in the automotive service and machining industry to check the flatness of machined mating surfaces.
Geometrical Product Specification and Verification (GPS&V) [1] is a set of ISO standards developed by ISO Technical Committee 213. [2] The aim of those standards is to develop a common language to specify macro geometry (size, form, orientation, location) and micro-geometry (surface texture) of products or parts of products so that the language can be used consistently worldwide.
For a precision machinist level with 2 mm (0.079 in) divisions, when the vial is tilted one division, the level will change 0.04 mm (0.0016 in) one meter from the pivot point, referred to by machinists as 5 tenths per foot. This terminology is unique to machinists and indicates a length of 5 tenths of 1 thousandth of an inch. [3] [4]