Measure the inside diameter of holes and cylindrical bores, as well as identify out-of-roundness problems. These gauges are often used to test engine cylinders, machine components, and other parts for issues with roundness and taper. They have the most common design for bore gauges—a two-point contact system. Even if the gauge is tilted, an internal pendulum balances the contact points at the true center of a hole. Hollow grips make these gauges easy to hold and prevent heat from your hands from skewing accuracy. For a long service life, the dial head has highly sensitive jeweled bearings that resist wear. Its plastic cover protects against scratches and drops.

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.

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.

No need for other tools to set a baseline diameter—these bore gauges have a built-in micrometer head. Use them to check diameters and test for issues with roundness in engine cylinders and other parts. 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 the dial head resist wear, and a plastic cover protects the head from scratches and drops. With hollow grips, these bore gauges are easy to hold and prevent heat from your hands from skewing accuracy.

To use them, set a baseline measurement with the micrometer head. As you move the gauge in the hole, the variation from the set measurement displays on the dial right away. Switch out the anvil to measure bores of different diameters.

Check for sizing errors in small slots and holes. These bore gauges show deviation from a set diameter measurement on the dial. They’re often used in precision manufacturing to test electronics and small-scale prototypes. The full-ball probe makes 360° contact inside of bores, making it easier to center in tight spots than anvil or spring-loaded contacts. Since it’s symmetrical, the ball is also less likely to tilt and skew measurements than a half-ball probe. The dial head has a plastic cover to protect it from drops and scratches.

Insert the probe into a bore and turn the knob on the handle to expand the contacts. To check size deviations, first 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. Use a micrometer to measure the distance across the contacts and get the bore diameter. Swap out the anvil to check bores of different diameters.

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 bore diameter directly. These gauges give you the actual diameter, unlike a dial bore gauge, which only shows the variation from a set measurement. An LCD display makes the diameter easy to read. They measure deeper into smaller holes than inside hole micrometers. To test holes of different sizes, swap among the included anvils. Each anvil has two contact points that detect issues with roundness and taper and a flat bottom for stability in blind holes. 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.

An SPC data output allows you to connect these gauges to a computer or data processor to analyze data and monitor measurements in real time. A zero-set button lets you start measuring at any point. All have zero-position memory, also known as absolute (ABS) positioning, which retains the measuring position when the gauge is turned off. These gauges have alarms to warn you about various issues, including a low battery and setting errors.

Extension rods (sold separately) lengthen the stem of your gauge to reach farther into deep bores.

Gauge blocks (sold separately) come in eight different metric sizes for calibrating your bore gauge.

Data cables (sold separately) connect your gauge to your PC to send data.

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.

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.

Check roundness, taper, and diameter near the bottom of bores—the flat bottom on these gauges positions the anvil against the base of the hole. Because they reach down into bores, they are a better choice for measuring deep holes than calipers or inside hole micrometers. They are comparison gauges—the dial will display the magnitude of variation from the set measurement. Set your desired measurement with a ring gauge, bore gauge calibrator, micrometer, or caliper.

The anvil on the gauges extends out and contacts two points to take measurements. Swap the included anvils to measure bores with different diameters. An internal pendulum keeps these gauges centered as they slide into a bore and positions the anvils perpendicular to the bore surface. This results in more contact with the bore for consistent and accurate measurements. These gauges have hollow grips for easy handling. They also prevent body heat from causing the material of the gauge to expand and impact accuracy. A plastic cover on the dial protects it from drops and scratches.

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.

With a short stem, these gauges easily maneuver in shallow holes and are compact enough to slip into your pocket. Use them to check the diameter and roundness of a hole. They are comparison gauges—the dial will display the magnitude of variation from the set measurement. Set your desired measurement with a ring gauge, bore gauge calibrator, micrometer, or caliper.

The anvil on the gauges extends out and contacts two points to take measurements. Swap the included anvils to measure bores with different diameters. These gauges have hollow grips for easy handling. They also prevent body heat from causing the material of the gauge to expand and impact accuracy. A plastic cover on the dial protects it from drops and scratches.

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.

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.