Measuring centre for design parameters

Abstract

Maximum material condition (MMC) is that condition of a part or feature which contains the maximum amount of material. The maximum material principle takes into account the mutual dependence of tolerances of size, form, orientation and/or location and permits additional tolerance as the considered feature departs from its maximum material condition. The free assembly of components depends on the combined effect of the actual finished sizes and the errors of form or position of the parts. Any errors of form or position between two mating parts have the effect of virtually altering their respective sizes. The symbol for maximum material condition is the letter M enclosed by a circle, which is positioned in the tolerance frame. The least material condition (LMC) is that condition of a part or feature which contains the minimum amount of material. The appropriate tolerance is quoted and followed by the letter L inside a circle. The limit of size, together with geometrical form or position of a feature, are factors of the maximum material principle, whose application is restricted to those features whose sizes are specified by toleranced dimensions incorporating an axis or median plane. The characteristics to which it can be applied include straightness, parallelism, squareness, angularity, position, concentricity, and symmetry.