Which precision measuring tool measures crankpin and main bearing journals for out-of-round wear?

The micrometer caliper is the appropriate choice for measuring crankpin and main bearing journals for out-of-round wear due to its high level of precision. This tool is specifically designed to provide accurate measurements of small dimensions, typically within a range of a few millimeters to several inches, and can measure thickness, diameter, and other precise dimensions with great accuracy.

When assessing out-of-round wear, what is crucial is the ability to measure the diameter at multiple points around the journal. The micrometer allows users to take multiple measurements and identify any deviations from a perfect circle, which is essential for diagnosing wear in engine components. Its anvil and spindle create a small measuring gap that can encompass small diameters, making it a preferred tool for engine mechanics and machinists when precision is necessary.

Other tools mentioned, like the vernier caliper and digital caliper, while useful for general measurements, do not provide the same level of precision that a micrometer does, especially for the specific task of measuring journal wear. The dial gauge is typically employed to measure displacement and can be useful in detecting variations from nominal sizes, but it is not primarily a tool for direct measurement of journal diameters. Thus, the micrometer stands out as the most suitable tool for this