Check a hole’s diameter and detect out-of-roundness problems. Often used to test engine cylinders and machine components, these gauges catch issues with roundness and taper. They have the most common design for bore gauges, which is a two-point contact system. The dial head’s highly sensitive jeweled bearings resist wear for a long service life.

To use these bore gauges, set a baseline measurement with a ring gauge, calibrator, micrometer, or caliper. The variation from the set measurement displays on the dial right away, so there’s no need for conversions. Swap out the anvil to measure bores of different diameters. Marked by size, the anvils are quick to spot and select.