Which of the following are the three basic tolerances commonly found on technical drawings?

• A. Bilateral, unilateral, and angular tolerances
• B. Limit dimensions, bilateral tolerance, and unilateral tolerance
• C. Maximum, minimum, and reference tolerances
• D. Bilateral, general, and fixed tolerances

Answer: (B)

The three basic tolerances commonly found on technical drawings are limit dimensions, bilateral tolerance, and unilateral tolerance. This reflects the standard ways to specify permissible variations in size and shape for parts being manufactured.

Limit dimensions are a way of expressing tolerances by providing two specific values that define the maximum and minimum acceptable limits for a dimension. This helps manufacturers understand the exact range within which a part must fall to be considered acceptable.

Bilateral tolerance allows for variation in both directions from a nominal dimension. For instance, if a part is specified with a nominal dimension of 10 mm and a bilateral tolerance of ±0.5 mm, the part can legally measure anywhere from 9.5 mm to 10.5 mm. This provides flexibility in manufacturing while ensuring that the part remains functional.

Unilateral tolerance, conversely, permits variation in one direction only, which can be critical in certain applications where deviations are constrained to avoid interference with other components. For example, if a dimension is specified as 10 mm +0.5 mm/-0 mm, the part can be no smaller than 10 mm but can be larger up to 10.5 mm.

The other choices incorporate various aspects of tolerancing but do not specifically represent the three basic types commonly