What is the proper tool for checking a bearing's diametral clearance?

The proper tool for checking a bearing's diametral clearance is the feeler gauge. This tool is specifically designed to measure gaps or clearances between parts, making it ideal for assessing the spacing inside a bearing assembly. When checking diametral clearance, you insert feeler gauge blades of known thickness into the gap between the bearing and the shaft or housing. If the feeler gauge fits snugly without force but does not exceed the gap, it provides a direct reading of the clearance.

While calipers and micrometers are precision tools used for measuring dimensions and can provide very accurate measurements, they are generally not suitable for measuring the clearance between moving parts directly. These tools measure the size of components rather than the gap itself. On the other hand, a tape measure, although useful for longer distances and larger dimensions, would not provide the necessary precision required for checking the close tolerances typically found in bearing assemblies. Thus, the feeler gauge stands out as the most appropriate and effective tool for this specific measurement.