Speed up thread tolerance checks—the handle on these gauges gives you a good grip to quickly thread and unthread go or no-go gauges. Use these gauges to make sure nuts, tapped holes, and other parts fall within tolerance. All are precisely manufactured to confirm thread fit. If the plug gauges wear down, you can insert new ones (not included) onto the taperlock handle.

A part is within tolerance if it’s easy to thread the go gauge into the part but difficult to thread the no-go gauge more than two turns.

Go gauges check the minimum internal thread size. No-go gauges check the maximum internal thread size. Go/no-go gauges have both a go gauge on one end of the handle and a no-go gauge on the other to speed up tests.

Gauges with a certificate of accuracy traceable to NIST include verification from the manufacturer that their thread sizes are within tolerance. The certificate is also known as a certificate of compliance or a short-form certification.

Gauges with a calibration certificate traceable to NIST were calibrated in a lab. The certificate, sometimes called a test report or long-form certificate, details the tested measurements.

Thread fit designates the tightness or looseness of mating threads. For inch threads, the higher the class number, the tighter the fit. 2B is standard for most imperial threads. These metric-threaded gauges are class 6H, which is comparable to the fit of those with class 2B.