What instrument is used to check the clearance of a spherical roller bearing?

The instrument used to check the clearance of a spherical roller bearing is a feeler gauge. Feeler gauges are thin, flat pieces of metal of varying thicknesses that are used to measure gap widths or clearances. In the context of spherical roller bearings, proper clearance is crucial for ensuring the correct operation of the bearing, minimizing wear, and prolonging its lifespan. By inserting the appropriate thickness of a feeler gauge into the clearance between the bearing and its housing, a technician can accurately determine if the spacing is within specifications.

While other options like Plastigauge also measure clearances, they serve different applications. Plastigauge is specifically used for measuring tight tolerances in engine assemblies and other applications where a precise measurement is required after assembly. Bluing is a method used to check alignment but does not provide clearance measurements. Babbitt is a material used for bearing surfaces, not a measuring device. Thus, the feeler gauge is the most suitable choice for checking the clearance in this scenario.