What are the upper and lower limits of a dimension referred to as?

• A. Tolerance margins
• B. Dimension ratios
• C. Tolerance limits or tolerance range
• D. Feature boundaries

Answer: (C)

The upper and lower limits of a dimension are referred to as tolerance limits or tolerance range. This terminology signifies the acceptable variation within a specified dimension, allowing for slight deviations without compromising the functionality or quality of the part being manufactured.

Tolerance limits define the maximum (upper) and minimum (lower) values that a dimension can be to still be considered acceptable. For example, if a part is designed with a dimension of 10 mm and a tolerance of ±0.2 mm, the upper limit is 10.2 mm, and the lower limit is 9.8 mm. Understanding tolerance limits is crucial in GD&T (Geometric Dimensioning and Tolerancing) because they help in ensuring that parts fit together correctly in assembly and function as intended in operation.

The other terms like tolerance margins, dimension ratios, and feature boundaries, while they may relate to aspects of dimensioning and tolerancing, do not specifically denote the concept of upper and lower limits of a dimension. Tolerance margins might refer to allowable variations but do not specifically indicate limits, dimension ratios focus on the relationship between dimensions rather than limits, and feature boundaries pertain more to geometric features rather than the numeric specifications of dimensions.