M12 Ring Gauges | McMaster-Carr

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Threaded Ring Gauges with Calibration Certificate

A certificate of calibration traceable to NIST states that these gauges have passed a test for accuracy. They’re for checking a part’s external threads to ensure they fall within tolerance.

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

Go gauges check the maximum external thread size.

No-go gauges check the minimum external thread size.

Threads have different classes of fit. Thread fit designates the tightness or looseness of the mating threads. For example, inch threads with a 3A fit have tighter tolerances than threads with a 2A fit.

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

Metric

					Go Gauge		No-Go Gauge
					Class 6g		Class 6g
Thread Size	Thread Type	Pitch	Hardness	Material		Each		Each
Class X
M12	Metric	1 mm	Rockwell C60	Tool Steel	00000000	0000000	00000000	0000000
M12	Metric	1.25 mm	Rockwell C60	Tool Steel	00000000	000000	00000000	000000
M12	Metric	1.5 mm	Rockwell C60	Tool Steel	00000000	000000	00000000	000000
M12	Metric	1.75 mm	Rockwell C60	Tool Steel	00000000	000000	00000000	000000

Threaded Ring Gauges

Check a part’s external threads to ensure they fall within tolerance.

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

Go gauges check the maximum external thread size.

No-go gauges check the minimum external thread size.

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

Metric

Go Gauge
Thread Size	Pitch	Hardness	Material	For Thread Fit	Pitch Dia. Tolerance		Each
Class X
M12	1 mm	Rockwell C60	Tool Steel	Class 6g	-0.008mm to 0mm	000000000	0000000
M12	1.25 mm	Rockwell C60	Tool Steel	Class 6g	-0.008mm to 0mm	00000000	000000
M12	1.5 mm	Rockwell C60	Tool Steel	Class 6g	-0.008mm to 0mm	000000000	000000
M12	1.75 mm	Rockwell C60	Tool Steel	Class 6g	-0.008mm to 0mm	000000000	000000
No-Go Gauge
Class X
M12	1 mm	Rockwell C60	Tool Steel	Class 6g	0mm to 0.008mm	000000000	000000
M12	1.25 mm	Rockwell C60	Tool Steel	Class 6g	0mm to 0.008mm	000000000	000000
M12	1.5 mm	Rockwell C60	Tool Steel	Class 6g	0mm to 0.008mm	000000000	000000
M12	1.75 mm	Rockwell C60	Tool Steel	Class 6g	0mm to 0.008mm	000000000	000000