Inspect a variety of hole sizes with the gauges in these sets. Each has spring-loaded contacts on the probe, which expand inside holes to measure diameter. These gauges also detect deviations in roundness, so they can help you make sure parts don’t wear prematurely or run inefficiently. Use them for general checks when testing engine cylinders, machine components, and turbines. 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.

The jaws on these micrometers work like caliper jaws to precisely measure inner diameters. These micrometers have a friction thimble with a constant-force mechanism, so they stop tightening once both jaws touch the sides for repeatable measurements. When the jaws stop tightening, the thimble continues turning with resistance, preventing overtightening. Use the included setting ring to calibrate and verify the accuracy of these micrometers.

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.

Detect variations in a range of hole diameters and depths. These sets include one dial head that fits onto three gauge bodies and 26 anvils to switch out for different holes. 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. An internal pendulum balances the contact points at the true center of a hole, even if the gauge is tilted. To prevent heat from your hands skewing accuracy, all the gauges have hollow grips, which also make them easy to hold. The dial head’s highly sensitive, wear-resistant jeweled bearings contribute to a long service life, and its cover protects against 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.

Measure hole diameter and read it directly on an LCD display, no baseline measurement required. They measure deeper into smaller holes than inside hole micrometers. These Mitutoyo sets include handles with digital displays, changeable heads, and setting rings. Rotate the display up to 330° to see results at the angle you need. Unlike the usual two contact points, the probe has three to center the head, which means more accurate tests for out-of-roundness. To protect against bumps and corrosion, the contact points have a titanium nitride (TiN) coating. A flat-bottom anvil gives you stability to check blind holes.

An SPC data output lets you connect the gauge to a computer or data processor to monitor data and analyze trends. Zero-position memory, also known as absolute (ABS) positioning, retains the measuring position when the gauge is turned off. A zero-set button lets you start measuring at any point. For repeatable go and no-go tests, set upper and lower tolerances. A bar indicator on the display shows whether your measurement is within bounds, making test results quick to check. Alarms will sound if there are any issues, such as setting errors and low battery.

Use the included setting rings to calibrate your gauge.

Additional heads (not included) are available to measure other bore sizes.

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.

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.

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

Measure the diameter of small holes, grooves, and recesses. These gauges help you find deviations in size or roundness that can cause precision parts, such as engine or valve cylinders, to wear quickly or run poorly. They have a full-ball probe, which has a 360° contact surface that’s easy to center in tight spaces. Compared to gauges with an anvil, spring-loaded contact, or half-ball probe, they’re less likely to tilt inside a bore and skew measurements.

Insert the probe into a bore and turn the knob on the handle to expand the contacts. Measure the distance across the contacts with a micrometer to find the bore diameter.

Measure the inside diameter of cylinders and rings. These micrometers have a plain thimble that turns freely without friction or a stopping device. It relies on user feel for accurate measurements. All include steel extensions that you can attach to one end of the micrometer head.

With an LCD screen, these micrometers make it easy to read inside diameter measurements taken from cylinders and rings. Place the micrometer inside your bore, then turn the thimble until the spindle makes contact with both sides. For an accurate reading, stop turning as soon as you feel resistance on the thimble.

Measure hole diameter in dirty machine shops and the outdoors with the pull of a trigger. Rated IP67, the bore gauge in these sets is protected from dust and temporary submersion in water. Sets include everything you need to measure—a pistol-grip gauge, heads of different measuring ranges, and setting rings. Thanks to its pistol grip, you can take measurements with one hand and reach into awkward angles, such as those overhead. The pistol grip also gives you precise control using just your fingertips instead of your whole hand. The LCD display directly shows the measured diameter, so you don’t need to set a baseline like you do with a dial bore gauge.

Instead of the standard two contact points, each head in these sets has three to center the probe in holes. This improves accuracy for detecting out-of-roundness, a common check for quality control. 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.

Use the included setting rings to calibrate your gauge.

Find the inside diameter of cylinders and rings. Rotate the plain thimble until it fits snugly inside the space you’re measuring. These micrometers rely on the operator to determine a secure fit to take accurate measurements. Attach one of the included extension rods to the micrometer head to measure in hard-to-reach spaces.

Test a variety of tight slots and holes in precision parts, such as electronics. These sets include a gauge with an LCD screen, an array of small head sizes, and setting rings. Unlike analog gauges, you don’t need a micrometer to find the diameter. Slide the full-ball probe into the hole and the diameter will show up directly on the screen, helping you detect issues with roundness. Since the probe makes 360° contact, it’s easier to center in small spots than anvils or spring-loaded contacts. It’s also less likely to tilt within a bore than a half-ball probe, which helps avoid skewed measurements. All sets come with a calibration certificate traceable to UKAS, which includes the test measurements that confirm accuracy. Choose a set with a wider measuring range to complete more measurement tasks using less tools.

The zero-set button allows you to start measuring at any point. Zero-position memory, also known as absolute (ABS) positioning, retains the gauge’s measuring position even when turned off. An SPC data output lets you connect these gauges to a computer or data processor to analyze data and monitor measurements in real time.

Use the settings rings to calibrate your gauge.

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.

Reach into bores to measure the precise size and location of grooves. These micrometers have two discs on their measuring spindle to find a groove’s edge. Slide the spindle into your bore, press the discs against the wall and into the groove, and twist the thimble to measure the distance between the two discs. A speeder knob moves the measuring spindle more quickly toward or away from your groove, without turning the thimble repeatedly. When the spindle touches the groove you’re measuring, it will stop tightening, but the speeder knob will continue turning with a clicking sound. The spindle doesn’t rotate, so the contact points won’t spin or slip out of a groove.