Define nominal size and actual size in engineering drawings.

• A. Nominal is the intended dimension; actual size is the measured dimension within tolerance
• B. Nominal is actual dimension; Actual is intended dimension
• C. Nominal is the measurement scale; Actual is a standard
• D. Nominal is a fixed value; Actual is always larger

Answer: (A)

Nominal size is the intended dimension designers use on the drawing as the target to achieve, while the actual size is the dimension you measure on the finished part. The drawing also specifies tolerances, which define how much the actual size may vary from the nominal target. So the actual size should fall within the tolerance range to be acceptable. For example, a hole with a nominal size of 0.500 inch and a tolerance of +0.005 / -0.000 could measure anywhere from 0.500 to 0.505 inch and still pass.

Other descriptions mix up these roles or make incorrect statements, such as claiming the actual size is always larger or that nominal is a measurement scale. In practice, the actual size can be either slightly larger or smaller than the nominal, as long as it stays within the specified tolerance.