What kind of tolerances should be used if deviation in one direction can cause issues?

Unilateral tolerances are ideal when a deviation in one direction can lead to significant problems. This tolerance type specifies a single direction in which variation is allowed, meaning that the dimension can either be greater than or less than a specified limit, but only within one direction. For instance, if a component has a maximum limit, it will not be allowed to exceed this limit, but can be slightly below it, ensuring strict control over parts that require precision in one direction.

Using unilateral tolerances helps in applications where exceeding a dimension could cause malfunctions, assembly issues, or product failures, while still allowing for a certain level of flexibility in the opposite direction. The clear restriction on one side prevents overly loose fits or inadequate clearances that might hinder the function of the part in its intended application.

In contrast, bilateral tolerances would allow deviations in both directions, which can be problematic in situations where specific fit or clearance is crucial. Geometric tolerances focus on the form and location of features rather than on size, and limit tolerances present a fixed range, which can be inadequate when strict control over a single direction is necessary.