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The two-dimensional measures above find one-dimensional counterparts in straightness measures, [5] defined by ISO 12780 on a cross-section (the plane curve resulting from the intersection of the surface of interest and a plane spanned by the surface normal): least squares reference line; minimum zone reference lines; local straightness deviation
Similarly, in shaft-straightening operations, where calibrated amounts of bending force are applied laterally to the shaft, the "total" emphasis corresponds to a bend of half that magnitude. If a shaft has 0.1 mm TIR, it is "out of straightness" by half that total, i.e., 0.05 mm.
Example of true position geometric control defined by basic dimensions and datum features. Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances via a symbolic language on engineering drawings and computer-generated 3D models that describes a physical object's nominal geometry and the permissible variation thereof.
ASME Y14.5 is a standard published by the American Society of Mechanical Engineers (ASME) to establish rules, symbols, definitions, requirements, defaults, and recommended practices for stating and interpreting Geometric Dimensions and Tolerances (GD&T). [1]
The statistical variation analysis model takes advantage of the principles of statistics to relax the component tolerances without sacrificing quality. Each component's variation is modeled as a statistical distribution and these distributions are summed to predict the distribution of the assembly measurement.
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.
Statistical tests are used to test the fit between a hypothesis and the data. [1] [2] Choosing the right statistical test is not a trivial task. [1] The choice of the test depends on many properties of the research question. The vast majority of studies can be addressed by 30 of the 100 or so statistical tests in use. [3] [4] [5]
Having a constant diameter, measured at varying angles around the shape, is often considered to be a simple measurement of roundness.This is misleading. [3]Although constant diameter is a necessary condition for roundness, it is not a sufficient condition for roundness: shapes exist that have constant diameter but are far from round.