Versatile enough for general checks, these bore gauges have spring-loaded contacts on the end of their probe to expand inside holes. They’re often used in vehicle repairs and to test parts, such as engine cylinders, for deviations in roundness that could lead to wear. Since they reach father into holes than calipers and inside-hole micrometers, these gauges make it easier to measure a deep hole’s diameter.

Once the contacts expand inside the hole, turn the screw on the handle to lock the contacts in place. To find the bore diameter, use a micrometer to measure the distance across the contacts.

Measure a variety of hole diameters. These sets include gauges that use spring tension to expand the probe’s contacts inside of bores. Each gauge has a different measuring range, so they’re useful for general checks. Use them to test engine cylinders, machine components, and turbines for deviations in roundness that could lead to wear or inefficiency. Designed to reach down into bores, they measure the diameter of deep holes better than calipers and inside-hole micrometers.

Once the contacts expand inside the hole, turn the screw on the handle to lock the contacts in place. To find the bore diameter, use a micrometer to measure the distance across the contacts.

Gauges with titanium-nitride (TiN) coated steel contact points are best when you may come into contact with the bottom of a hole, or when working in harsh environments. They resist wear better than gauges with steel contact points.