A go and no-go gauge in one, these gauges check that left-hand threads fall within tolerance. Use them to confirm thread fit for nuts, tapped holes, and other parts. The taperlock handle speeds up tests, giving you a good grip to thread and unthread each gauge end. It also lets you swap out worn gauges for new ones (not included) on either end.

The go gauge checks the minimum internal thread size, and the no-go gauge checks the maximum. A part is within tolerance if it’s easy to thread the go gauge but difficult to thread the no-go gauge more than two turns.

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 and works for most applications. For metric threads, the higher the class number, the looser the fit. 6H is the metric standard and works for most applications.

For technical drawings and 3-D models, click on a part number.

Check that holes tapped for helical threads are within tolerance. You’ll sometimes hear these threads referred to as Screw Thread Insert (STI) threads. To speed up tests, these gauges have a go gauge on one end and a no-go gauge on the other. The double-ended taperlock handle makes them quick to thread and unthread. It also lets you swap in new plug gauges (not included) in place of worn ones.

The go gauge checks the minimum internal thread size, and the no-go gauge checks the maximum. A part is within tolerance if it’s easy to thread the go gauge but difficult to thread the no-go gauge more than two turns.

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.

For technical drawings and 3-D models, click on a part number.