What term describes the difference between maximum material limits of mating parts?

The term that describes the difference between the maximum material limits of mating parts is "Allowance." Allowance specifically refers to the intentional difference in size between the two mating components, which is designed to ensure a specific fit, such as clearance or interference, during operation. It quantifies the amount by which one part is allowed to deviate from an established standard or size to achieve the desired functional relationship with a mating part.

In contrast, tolerance pertains to the permissible limit or variation in a part's dimensions, indicating how much a dimension can vary from the specified size overall. Fits describe the relationship between the sizes of two mating parts, categorizing them as either clearance, interference, or transition fits. Variance, on the other hand, typically refers to statistical measures of how much values in a set differ, which does not specifically relate to mechanical part dimensions in the same context.

Understanding allowance is crucial in machine design, as it directly influences the performance and reliability of assembled components, ensuring they function correctly in the intended application.