Which statement correctly describes unilateral tolerances?

Which statement correctly describes unilateral tolerances?

• A. A unilateral tolerance allows variation in only one direction from the basic size.
• B. A unilateral tolerance allows equal variation in both directions from the basic size.
• C. A unilateral tolerance allows any variation without direction.
• D. A unilateral tolerance fixes the dimension exactly.

Answer: (A)

Unilateral tolerances let allowable variation occur in only one direction from the nominal size. That means you choose either a plus or a minus limit, but not both, so the size can move only larger than the basic size or only smaller than it. For example, with a basic size of 10.00 and a unilateral tolerance of +0.05/0, the acceptable range is 10.00 to 10.05. If the tolerance is -0.05/0, the range is 9.95 to 10.00. This is different from a bilateral tolerance, which allows equal variation in both directions (for instance, ±0.05 would give 9.95 to 10.05). The idea of any variation without direction or fixing the dimension exactly doesn’t describe unilateral tolerancing.

Unilateral tolerances let allowable variation occur in only one direction from the nominal size. That means you choose either a plus or a minus limit, but not both, so the size can move only larger than the basic size or only smaller than it.

For example, with a basic size of 10.00 and a unilateral tolerance of +0.05/0, the acceptable range is 10.00 to 10.05. If the tolerance is -0.05/0, the range is 9.95 to 10.00. This is different from a bilateral tolerance, which allows equal variation in both directions (for instance, ±0.05 would give 9.95 to 10.05). The idea of any variation without direction or fixing the dimension exactly doesn’t describe unilateral tolerancing.