Bore Gauges

Bore gauges, also known as a bore measuring tool, hole measuring tool, drill gauge, hole gauge or dial bore gauge set, are precision measuring tools designed specifically for the accurate measurement of holes (or bores).

They are a key instrument in any engineer’s or machinist’s toolkit. These diameter-measuring devices come in a variety of forms and sizes, allowing professionals to easily and accurately measure a vast range of internal hole diameters.

Types of Bore Gauges

Bore gauges are designed with different mechanics to suit various accuracy needs and hole characteristics. Below are some of the most common types used in precision measurement.

Dial Bore Gauges

These gauges use a dial indicator to display the measurement, allowing for high-precision readings and easy detection of any ovality or taper in the bore. They must be zeroed against a known standard, like a setting ring or a micrometer, before use.

Digital Bore Gauges

Similar to dial bore gauges, these types of bore measuring tools feature a digital display that provides the measurement directly, often with the ability to switch between metric and imperial units. They offer high resolution and can easily interface with data collection systems for statistical process control.

Telescopic Bore Gauges

Often called "T-gauges," these tools feature a handle and two spring-loaded plungers that expand to contact the bore walls. The gauge is locked in place and removed from the hole, and then the final dimension across the plungers is measured with an external tool, such as a micrometer.

Taper Bore Gauges

These are precisely machined, cone-shaped tools used to measure the diameter of a hole at specific depths or to check for the uniformity of a taper. These types of bore gauges are simply inserted into the hole until a tight fit is achieved, and the diameter is read directly from markings on the gauge body.

Pin Gauge Sets

A pin gauge set consists of a range of small, cylindrical gauges of fixed, precisely known diameters, typically sold in small, incremental steps. They are primarily used for quickly checking the go/no-go tolerance of small holes to determine if the bore falls within an acceptable range.

Key Features to Consider When Choosing a Bore Gauge Set

Selecting the appropriate bore gauge set is crucial for ensuring reliable and accurate measurements in your machining or inspection tasks. Pay close attention to the following features to match the tool to your specific measurement requirements:

• Measuring Range: Ensure the bore or hole gauge set covers the full range of internal diameters (or bore sizes) you regularly need to measure.
• Accuracy: Choose a bore measuring tool with the required level of precision (e.g. 0.001m or 0.0001in) depending on the strictness of your tolerance specifications.
• Contact Points: Consider the number of contact points (two-point for smaller sizes, three-point for better self-centering) and their tip material (e.g., carbide-tipped for durability).
• Material: Consider the level of durability you need for your bore measuring tool, especially for parts like the measuring head and gaging contacts.
• Calibration Standards: Check if the hole gauge set or dial bore gauge set includes necessary setting rings or master gauges to ensure the bore gauge can be correctly and reliably zeroed before use.
• Portability: For field work or ease of use, consider how the bore gauge is organised and stored, ensuring the delicate instruments are protected from damage.
• Depth and Clearance: Verify the gaging depth the tool can reach and ensure the measuring head can fit into any narrow or recessed bores you need to inspect.

Applications of Bore Gauges

Bore gauges are indispensable tools across numerous industries in New Zealand (NZ) where precise internal diameter measurement is critical for quality control, performance, and safety. Their primary function is ensuring components meet strict dimensional tolerances.

• Automotive and Engine Repair: Bore gauges are crucial for measuring cylinder bores during engine rebuilding to ensure the correct piston and ring clearances, checking for ovality, taper, or wear, which is vital for engine performance and longevity.
• Manufacturing and Quality Control: Used extensively in New Zealand's precision manufacturing sectors to check the true diameter and straightness of machined parts like sleeves, bushings, and gear housings to guarantee components fit together correctly.
• Hydraulics and Pneumatics: Essential for confirming the internal dimensions of cylinder barrels and valve bodies, ensuring the seals and pistons operate efficiently without leakage or binding in hydraulic systems.
• Aerospace Industry: In the demanding aerospace sector, these gauges perform high-accuracy inspection of critical components like jet engine parts and landing gear mechanisms, where extremely tight micrometre-level tolerances are non-negotiable for safety.
• Tool and Die Making: Utilised by machinists and toolmakers to verify the precise size of holes in jigs, fixtures, and molds, guaranteeing the consistency and accuracy of the final products they are designed to produce.

Shop Precision Bore Gauges at RS for Accurate Measurements

To achieve the uncompromising accuracy required in machining, automotive, and manufacturing applications, you need access to the best precision bore gauges in NZ.

RS carries a comprehensive and wide-ranging selection of all bore gauge types, including dial bore gauges, digital bore gauges, drill gauges and more. We stock single bore measuring tools to complete dial bore gauge sets from top brands like Vogel, Starrett, and our very own RS PRO.

Beyond bore gauges, RS also stocks all the complementary products essential for precision work, such as long nose pliers, wire crimpers, torque wrenches and more. For more information on our delivery options and fees, visit our delivery page.