If a gauge is not zeroed correctly before measuring, what is the likely outcome?

• A. Readings may be biased, leading to incorrect tolerances
• B. It has no effect
• C. Measurements will be more accurate
• D. It reduces tool wear

Answer: (A)

Not zeroing a gauge leaves a zero error that biases every measurement. When you set the gauge to true zero on a standard, all readings reflect the actual size being measured. Without that initial alignment, the instrument’s offset is added to every measurement, creating a systematic error that shifts results in one direction. The practical result is that parts might seem larger or smaller than they truly are, leading to incorrect tolerances being applied. For example, a positive offset could make a true 1.000 inch dimension read as 1.005 inches, making a part appear oversized. A negative offset does the opposite. Zeroing eliminates this bias, ensuring measurements reflect the true size. It’s not about having no effect, nor about increasing accuracy by itself, and it doesn’t affect tool wear.