A different measuring range on each gauge makes these sets handy for checking a variety of hole sizes. Each gauge has spring-loaded contacts on the probe, which expand inside holes to measure diameter. Often used for general checks, these sets can make sure that engine cylinders, machine components, and turbines don’t deviate in roundness, which could lead to wear and inefficiency if undetected. Since the gauges reach into holes farther than calipers and inside-hole micrometers, they make it easier to inspect deep holes.

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.

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.

Check the diameter of holes with the pull of a trigger. These Starrett sets have everything you need for one-handed measurements—a pistol-grip gauge, heads for varying diameters, and setting rings. Thanks to its pistol grip, you can reach the gauge into awkward spots, such as those overhead. The pistol grip also gives you precise control using just your fingertips instead of your whole hand. Unlike dial bore gauges, you can measure right away, no baseline measurement required. You can even set upper and lower tolerances for quick go/no-go tests. The LCD display has lights and arrows to show if the hole falls within your set tolerance. Rotate the display to read results at the angle you need.

Since the gauge has three contact points, it’s more accurate than a typical bore gauge with two contact points. The probe centers itself, so it’s easier to detect issues with roundness, a common check in quality control tests. To stay accurate, the gauge has alarms to warn you about problems that could skew readings, such as a low battery, a contaminated probe, and test setting errors. Use the included setting rings to calibrate your gauge.

With a zero-set button, you can start measuring at any point. Zero-position memory, also known as absolute (ABS) positioning, retains the measuring position when the gauge is off. Connect the gauge to your computer, smartphone, or other device via Bluetooth or the SPC data output to monitor and analyze data in real time.

Make sure the top diameter of a chamfered hole isn’t too big or too small. These gauges are often used as a quality control check after milling, drilling, and reaming. Press the three-blade probe into a chamfered hole and twist slightly to center. Once the blades touch the hole’s slopes, the dial will display the diameter. Zero set these gauges on a flat, ground surface when needed.

Choose a gauge with a measuring angle that’s greater than or equal to the angle of the chamfered hole you’re measuring.

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

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.