Lo Gauges | McMaster-Carr

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Thread Size

Thread Fit

Unified Standard Class 2A

Unified Standard Class 3A

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Thread Direction

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Accuracy Certificate Traceable to NIST

Calibration Certificate Traceable to NIST

Export Control Classification Number (ECCN)

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DFARS Specialty Metals

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236 Products

Threaded Ring Gauges

Check a part’s external threads to make sure they fall within tolerance. You can use these for bolts, threaded rods, bits, and more. All gauges come with a manufacturer’s certificate of accuracy, also known as a certificate of compliance or a short form certification, that verifies the thread sizes are within tolerance.

The part is within tolerance if it’s easy to thread a go gauge onto, but difficult to thread a no-go gauge more than two turns. Use a threaded ring gauge holder to keep two gauges on hand at once for faster inspection.

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.

Inch

						No-Go Gauge
Thread Size	Thread Type	Hardness	Material	Choose a For Thread Fit	Thread Direction	Pitch Dia. Tolerance		Each
Class X
0-80	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	0000000
1-64	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0002"	00000000	000000
1-72	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
2-56	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
2-64	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
3-48	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0002"	00000000	000000
3-56	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
4-40	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
4-48	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
5-40	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
5-44	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
6-32	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
6-40	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
8-32	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
8-36	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0002"	00000000	000000
10-24	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
10-32	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
12-24	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0003"	00000000	000000
12-28	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
12-32	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/4"-20	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/4"-28	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/4"-32	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/16"-18	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/16"-24	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/16"-32	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/8"-16	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/8"-24	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/8"-32	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
7/16"-14	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0003"	00000000	000000
7/16"-20	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
7/16"-28	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/2"-13	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/2"-20	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1/2"-28	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
9/16"-12	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0003"	00000000	000000
9/16"-18	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
9/16"-24	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/8"-11	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/8"-18	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
5/8"-24	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
11/16"-24	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/4"-10	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/4"-16	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
3/4"-20	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
7/8"-9	UNC	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
7/8"-14	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
7/8"-20	UNEF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1"-8	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0004"	00000000	000000
1"-12	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1"-14	UNS	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0003"	00000000	000000
1"-14	UNS	Rockwell C60	Tool Steel	Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1"-20	UNEF	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0003"	00000000	000000
1 1/8"-7	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0004"	00000000	000000
1 1/8"-12	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1 1/4"-7	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0004"	00000000	000000
1 1/4"-12	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1 1/2"-6	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0004"	00000000	000000
1 1/2"-12	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000
1 3/8"-6	UNC	Rockwell C60	Tool Steel	Class 2A	Right Hand	0" to 0.0004"	00000000	000000
1 3/8"-12	UNF	Rockwell C60	Tool Steel	Class 2A, Class 3A	Right Hand	0" to 0.0003"	00000000	000000

Metric

						No-Go Gauge
Thread Size	Pitch	Hardness	Material	For Thread Fit	Thread Direction	Pitch Dia. Tolerance		Each
Class X
M1.6	0.35 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	0000000
M2	0.4 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M2.2	0.45 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M2.5	0.45 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M3	0.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M3.5	0.6 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M4	0.7 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M4.5	0.75 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M5	0.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.005 mm	000000000	000000
M5	0.8 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M6	0.75 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M6	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M7	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M8	0.75 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M8	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M8	1.25 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M9	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M9	1.25 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M10	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M10	1.25 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M10	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M11	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M11	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M12	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M12	1.25 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M12	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M12	1.75 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M14	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M14	1.25 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M14	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M14	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M16	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M16	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M16	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M18	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M18	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M18	2.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M20	1 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M20	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M20	2.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M22	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M22	2.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M24	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M24	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M24	3 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M26	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M27	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M27	3 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M30	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M30	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M30	3.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M33	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M33	3.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M35	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M36	1.5 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M36	2 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000
M36	4 mm	Rockwell C60	Tool Steel	Class 6g	Right Hand	0 mm to 0.008 mm	000000000	000000

Threaded Ring Gauges with Calibration Certificate

Not only were these gauges calibrated in a lab, but they also come with a certificate that's traceable to NIST. The certificate, sometimes called a test report and long form certificate, details the tested measurements. 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. Inspect faster by holding more than one ring gauge with a threaded ring gauge holder.

No-go gauges check the minimum external thread size.

Inch—Class X

					No-Go Gauge
Thread Size	Thread Type	Thread Direction	Hardness	Material	Pitch Dia. Tolerance		Each
For Thread Fit Class 2A
3-56	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0002"	00000000	0000000
5-44	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0002"	00000000	000000
12-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1/4"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
5/16"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
3/8"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
7/16"-28	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1/2"-28	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
9/16"-12	UNC	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
9/16"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
5/8"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
11/16"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
3/4"-20	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
7/8"-20	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1"-14	UNS	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1"-20	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1 1/8"-7	UNC	Right Hand	Rockwell C60	Tool Steel	0" to 0.0004"	00000000	000000
1 3/8"-6	UNC	Right Hand	Rockwell C60	Tool Steel	0" to 0.0004"	00000000	000000
1 3/8"-12	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
For Thread Fit Class 3A
3-56	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0002"	00000000	000000
5-44	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0002"	00000000	000000
12-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1/4"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
5/16"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
3/8"-32	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
7/16"-28	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1/2"-28	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
9/16"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
5/8"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
11/16"-24	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
3/4"-20	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
7/8"-20	UNEF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1"-14	UNS	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000
1 3/8"-12	UNF	Right Hand	Rockwell C60	Tool Steel	0" to 0.0003"	00000000	000000

Metric—Class X

					No-Go Gauge
Thread Size	Pitch	Thread Direction	Hardness	Material	Pitch Dia. Tolerance		Each
For Thread Fit Class 6g
M2.2	0.45 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.005 mm	00000000	0000000
M4.5	0.75 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M5	0.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.005 mm	00000000	000000
M6	0.75 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M8	0.75 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M9	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M9	1.25 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M10	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M11	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M11	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M14	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M14	1.25 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M14	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M16	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M18	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M18	2.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M20	1 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M20	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M20	2.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M22	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M22	2.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M24	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M24	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M24	3 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M26	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M27	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M27	3 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M30	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M30	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M30	3.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M33	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M33	3.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M35	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M36	1.5 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M36	2 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000
M36	4 mm	Right Hand	Rockwell C60	Tool Steel	0 mm to 0.008 mm	00000000	000000

Threaded Ring Gauge Holders

Join two ring gauges with different sizes to quickly check if threads are within tolerance. Secure your gauges to these holders with the included fasteners.

Inch

For Thread Dia.	Overall Lg.	Material	Color		Each
No. 0, No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 8, No. 10, No. 12	1"	Aluminum	Black	0000000	000000
1/4", 5/16"	1 3/8"	Aluminum	Black	0000000	00000
3/8", 7/16", 1/2"	1 3/4"	Aluminum	Black	0000000	00000
9/16", 5/8", 11/16", 3/4"	2 1/4"	Aluminum	Black	0000000	00000
7/8", 1", 1 1/8"	2 5/8"	Aluminum	Black	0000000	00000
1 1/4", 1 3/8", 1 1/2"	3 1/4"	Aluminum	Black	0000000	00000

Metric

For Thread Dia.	Overall Lg.	Material	Color		Each
M1.6, M2, M2.2, M2.5, M3, M3.5, M4, M4.5, M5	1"	Aluminum	Black	0000000	000000
M6, M7, M8, M9	1 3/8"	Aluminum	Black	0000000	00000
M10, M11, M12	1 3/4"	Aluminum	Black	0000000	00000
M14, M16, M18, M20	2 1/4"	Aluminum	Black	0000000	00000

Left-Hand Threaded Ring Gauges

Test if the left-hand threads on parts fall within tolerance. These gauges are often used with parts such as screws, bolts, and threaded rods. All come with a manufacturer’s certificate of accuracy, also known as a certificate of compliance or a short-form certification, that verifies the thread sizes are within tolerance.

No-go gauges check the minimum external thread size.

Thread fit designates the tightness or looseness of mating threads. For inch threads, the higher the class number, the tighter the fit. These metric-threaded ring gauges are class 6g, which is comparable to the fit of those with class 2A threads.

Inch—Class X

				No-Go Gauge
Thread Size	Thread Type	Hardness	Material	Pitch Dia. Tolerance		Each
For Thread Fit Class 2A
6-32	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	0000000
8-32	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
10-24	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
10-32	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/4"-20	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/4"-28	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/16"-18	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/16"-24	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/8"-16	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/8"-24	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
7/16"-20	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/2"-13	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/2"-20	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/8"-11	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/8"-18	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/4"-10	UNC	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/4"-16	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1"-8	UNC	Rockwell C60	Tool Steel	0" to 0.0004"	0000000	000000
1 1/4"-12	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
For Thread Fit Class 3A
10-32	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/4"-28	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/16"-24	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/8"-24	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
7/16"-20	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1/2"-20	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
5/8"-18	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
3/4"-16	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000
1 1/4"-12	UNF	Rockwell C60	Tool Steel	0" to 0.0003"	0000000	000000

Metric—Class X

				No-Go Gauge
Thread Size	Pitch	Hardness	Material	Pitch Dia. Tolerance		Each
For Thread Fit Class 6g
M5	0.8 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	0000000
M6	1 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M8	1.25 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M10	1.25 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M10	1.5 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M12	1.25 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M12	1.75 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M14	1.5 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M16	1.5 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000
M16	2 mm	Rockwell C60	Tool Steel	0 mm to 0.008 mm	0000000	000000