What is another term for plus or minus tolerance?

Bilateral tolerance refers to the system of providing a range around a nominal dimension, where the permissible variation can be both above and below the nominal value. This means that a part can be allowed to be larger or smaller than a specified dimension within defined limits. For example, if a shaft has a nominal diameter of 50 mm with a bilateral tolerance of ±0.5 mm, the acceptable size would range from 49.5 mm to 50.5 mm.

Understanding bilateral tolerance is important in manufacturing and engineering because it allows for some leeway in part dimensions, ensuring that components can fit and function together properly while accounting for manufacturing variations. This flexibility is crucial in achieving the desired assembly and performance of mechanical systems.

In contrast, other terms such as total tolerance, unilateral tolerance, and allowance refer to different concepts in tolerance specifications. Total tolerance encompasses the entire range of permissible dimensions, unilateral tolerance restricts variation to one direction (either only positive or only negative), and allowance represents the intentional difference between mating parts to ensure fitting.