Insert into small bores, slots, grooves, and recesses and turn the knob on the handle to expand the contacts. To find the bore diameter, use a micrometer to measure the distance across the contacts.

Full-ball gauges are best for deep bores.

Half-ball gauges are best for flat, shallow areas.

Insert into small bores, slots, grooves, and recesses and turn the knob on the handle to expand the contacts. To find the bore diameter, use a micrometer to measure the distance across the contacts. The full-ball design makes these gauges good for measuring deep bores.

These calipers come with a calibration certificate traceable to NIST that states they've passed a test for accuracy. Short, narrow contacts allow them to take hard-to-reach measurements, such as the dimensions of internal grooves and slots. All are IP67 rated for protection from dust and temporary water submersion. They have a zero-set button which allows you to start measuring at any point.

Short, narrow contacts allow these calipers to take hard-to-reach measurements, such as the dimensions of internal grooves and slots. They are IP67 rated for protection from dust and temporary water submersion. Each has a zero-set button which allows you to start measuring at any point.

Short, narrow contacts allow these calipers to take hard-to-reach measurements, such as the dimensions of internal grooves and slots.

Measure the inside diameter of holes and cylindrical bores, as well as identify out-of-roundness problems. Switch between anvils to measure holes of different diameters. They have highly sensitive, wear-resistant jeweled bearings for a long service life.

Use these bore gauges to measure the inside diameter of holes and cylindrical bores, as well as identify out-of-roundness problems. Switch between anvils to measure bores of different diameters. All have highly sensitive, wear-resistant jeweled bearings for a long service life.

For technical drawings and 3-D models, click on a part number.

Set includes one dial head that fits onto three gauge bodies. Use these to measure the inside diameter of holes and cylindrical bores, as well as identify out-of-roundness problems. Switch between anvils to measure holes of different diameters. The dial head has highly sensitive, wear-resistant jeweled bearings for a long service life.

Find the inside diameter of cylinders and ring. These micrometers have a plain thimble, which relies on operator feel for accurate measurements.

124 series have solid steel extensions that attach at one end of the micrometer head.

823 series have lightweight tubular extensions that can attach at either end of the micrometer head.

Width markings on the leaves let you for check diameters and widths. Sets include leaves in a variety of thicknesses riveted together in a fan design that folds up for portability.