Maximum material and least material requirements
Colin H. Simmons, Dennis E. Maguire, Neil Phelps
2020
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Key Takeaway Key Takeaway: Maximum Material Condition (MMC) and Least Material Condition (LMC) are used to describe the maximum amount of material in a part or feature, and their relationship with geometrical tolerances.
Abstract
Abstract Maximum Material Condition (MMC) exists when a part or feature contains the maximum amount of material everywhere, e.g. minimum size hole, or maximum size shaft. In certain cases, its use allows an increase in the specified tolerance (often termed a bonus tolerance) if it is indicated that the tolerance applies to the feature at its maximum material condition. The maximum material requirement takes into account the mutual dependence of tolerances of size, form, orientation and/or location and permits additional geometrical tolerance as the part or feature departs from its maximum material condition. Least Material Condition (LMC) is that condition of a part or feature which contains the minimum amount of material, e.g. maximum size hole or a minimum size shaft. Circumstances do arise where, for example, a designer would want to limit the minimum wall thickness between a hole and the side of a component. This chapter identifies the geometrical tolerances for which MMC can be applied with illustrated examples and those that it cannot.