Which tool can determine piston pin out-of-round wear?

The micrometer caliper is specifically designed for measuring small dimensions with high precision, making it the ideal tool for determining out-of-round wear on a piston pin. When assessing out-of-round wear, it is essential to measure the diameter of the piston pin at multiple points around its circumference. The micrometer caliper allows for this due to its ability to provide accurate and consistent measurements, typically within one thousandth of an inch.

Using this tool, a technician can detect deviations from the standard measurement, indicating wear or imperfections in the piston pin. The precision of a micrometer caliper in measuring these small variances is crucial for engine performance and longevity, as an out-of-round piston pin can lead to increased friction, abnormal wear, and potentially catastrophic engine failure.

In contrast, while a vernier caliper also provides precise measurements, it is generally less accurate than a micrometer for very small dimensions. A machinist scale is suitable for rough measurements but lacks the precision required for fine-tuning parts like piston pins. A thickness gauge is used primarily for measuring material thickness, not for determining the geometric integrity of round components. Therefore, the micrometer caliper stands out as the most effective tool for this particular measurement task.