Class 3A Ring Gauges | McMaster-Carr

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234 Products

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.

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.

Inch—Class X

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

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.

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.

Inch

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

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.

Go gauges check the maximum external thread size.

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.

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

Inch—Class X

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

Left-Hand Threaded Ring Gauges with Calibration Certificate

Calibrated in a lab and backed by a certificate traceable to NIST, these gauges check if left-hand threads fall within tolerance. The certificate, sometimes called a test report and long-form certificate, details the tested measurements. Use these gauges on screws, threaded rods, and other parts with external threads. For faster tests, hold more than one ring gauge with a threaded ring gauge holder.

Your part is within tolerance if it’s easy to thread a go gauge onto it 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.

Inch—Class X

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