Check a variety of hole, groove, and slot diameters. Each gauge in these sets has a different measuring range. The end of these gauges has a 360° contact surface that’s easier to center in tight spaces than anvils or spring-loaded contacts. Use them to measure slots and bores in precision parts, such as electronics, where small size deviations can cause inefficiencies.

Insert the probe into a bore 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. They’re less likely than half-ball gauges to tilt within the bore, which helps to avoid skewed measurements caused by placing the gauge off-center.

Half-ball gauges are best for measuring near the bottom of flat, shallow bores.

Find the inside diameter of cylinders and rings. 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.

Collars (sold separately) extend a micrometer’s measuring range. Handles (sold separately) screw into a micrometer head to extends its reach for measuring deep holes.

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

Use the Starrett gauge blocks in these sets individually or together to take precise measurements or calibrate your measuring tools. They are often used to mark layouts, align machine components, and check that parts are within tolerance. All have been laboratory calibrated and include NIST traceable certification with the tested measurements. The blocks are individually numbered for recalibration.

Each block has a grade per ASME B89.1.9. Grades are based on tolerance—the smaller the tolerance, the greater the accuracy. Grade 0 means these gauge blocks are our most accurate. They help verify that precise measuring instruments, such as micrometers and calipers, are taking accurate readings.

Use a gauge block holder (not included) to create a custom repeatable measurement by stacking multiple blocks together. To prevent your gauge block combinations from wearing down over time, add wear blocks (not included) on each end.

Square blocks have a hole that runs through their center. Stack multiple square blocks together and secure them with a rod (not included).

Steel blocks are the most common choice. Ceramic blocks are more resistant to wear and corrosion than steel blocks. They won’t expand or contract as temperatures change. Use them in cleanrooms—they’re nonmagnetic so they won’t pick up any iron or dust.