Which of the following is NOT considered a basic tolerance?

• A. Bilateral tolerance
• B. Unilateral tolerance
• C. Geometric tolerance
• D. Limit dimensions

Answer: (C)

The correct response identifies geometric tolerance as not being classified as a basic tolerance. To understand this, it's essential to recognize the definitions and characteristics of basic tolerances. Basic tolerances typically include bilateral tolerance, unilateral tolerance, and limit dimensions, which all involve defining the acceptable variations in size or location of a feature.

Bilateral tolerance allows for variation in both directions from a nominal size, while unilateral tolerance restricts the variation to one direction. Limit dimensions provide upper and lower bounds for a dimension without specifying a tolerance zone. These are all measures of size that directly relate to how much a part can deviate from a specified dimension.

In contrast, geometric tolerance specifies the allowable variation in form, orientation, location, and runout for part features, rather than just their dimensions. It defines how a feature relates to other features and is represented in a different way than basic dimensional tolerances. Therefore, geometric tolerance does not fit the category of basic tolerances, making it the correct choice in identifying what is NOT considered a basic tolerance.