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.

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.

Test for size deviations across a range of hole diameters. These sets include 3 gauges and over 25 anvils marked by size for quick changes. Use them to test engine cylinders, machine components, and other parts for issues with roundness and taper. They have a two-point contact system, which is the most common design for bore gauges. For a long service life, the jeweled bearings in each dial head resist wear, and a plastic cover protects the head from scratches and drops.

Check size deviations by first setting the desired measurement with a ring gauge, bore gauge calibrator, micrometer, or caliper. The dial will display the magnitude of variation from the set measurement.

The dial on these gauges displays size deviations in real time. These gauges measure small slots and bores in precision parts, such as electronics, where even small size deviations can cause inefficiencies. Thanks to its full-ball design, the end of these gauges makes 360° contact inside the bore, so it's easier to center in tight spaces than anvil or spring-loaded contacts. This symmetrical ball is also less likely to tilt within the bore than half-ball gauges, which helps to avoid skewed measurements from improper placement.

Insert the probe into a bore and turn the knob on the handle to expand the contacts. To check size deviations, set the desired measurement with a ring gauge, bore gauge calibrator, micrometer, or caliper. The dial will display the magnitude of variation from the set measurement. To find the bore diameter, use a micrometer to measure the distance across the contacts.

Check slot widths and hole diameters with the markings on these gauges. Leaves in a variety of sizes are riveted together in a fan design—spread them out for use or fold them in for portability. Each leaf narrows toward the tip to measure a range of sizes. Slide them into a hole until the gauge sits snug and then read the width measurement.

Mate your fastener and countersink perfectly for a secure hold with these Starrett gauges. They are often used in vehicle and metal manufacturing to check the top diameter and countersink angle of a hole. When the conical probe touches the hole’s angled walls, the diameter will display on the dial. You can verify the countersink angle based on how snug the probe fits into the hole. Even when you lift the gauge out of the hole, your measurement will stay on the dial until you press the reset button.

Choose a gauge with an angle that’s equal to the angle of the countersunk hole you’re trying to measure.

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

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.

Reach deep into small holes and slots for precise depth measurements. This gauge has a rod to measures the depth of recesses where the blade won’t fit. The blade has a hook which grabs the edge of an object for easy alignment. Markings are etched for wear resistance.

An LCD display helps you read depth measurements of drilled holes and machined slots. These gauges are often used for quality control in manufacturing plants and laboratories. Store data internally or use the SPC data output to connect to a computer or data processor. This allows you to analyze data and monitor measurements in real time. The zero-set button lets you start measuring at any point. With zero-position memory, also known as absolute (ABS) positioning, these gauges retain their measuring position when the scale is off. To save battery life, they turn off after 30 minutes of inactivity.

Precisely measure shallow holes, slots, and recesses without any fine adjustments. Simply press these gauges against the bottom surface and push a button to measure. The LCD display makes measurements easy to read. Shaped to fit your palm, these gauges are also comfortable to hold and position. Store measurements on the gauge or wirelessly send them to a computer or data processor up to 30 ft. away using the built-in transmitter. With SPC data output, you can remotely analyze data and monitor measurements in real time.

A zero-set button lets you start measuring at any point. With zero-position memory, also known as absolute (ABS) positioning, these gauges retain their measuring position when the scale is off. To save battery life, they turn off after 20 minutes of inactivity.

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.

Measure the depth of holes, slots, shoulders, and projections by changing out the steel extension rods supplied in 1" incremental lengths. The thimble has a constant-force mechanism, so that once the spindle contacts the surface of the measured object, it will stop tightening. This ensures repeatable measurements and prevents over-tightening.

These micrometers come with a calibration certificate traceable to NIST that states they've passed a test for accuracy. Change out the steel extension rods supplied in 1" incremental lengths to measure the depth of holes, slots, shoulders, and projections. The thimble has a constant-force mechanism, so that once the spindle contacts the surface of the measured object, it will stop tightening. This ensures repeatable measurements and prevents over-tightening.