Thread Gauges STI | McMaster-Carr

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Accuracy Certificate Traceable to NIST

Calibration Certificate Traceable to NIST

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UNC

UNF

Gauge Measurement Type

No-Go

RoHS

Compliant

REACH

Compliant

U.S.–Mexico–Canada Agreement (USMCA) Qualifying

Yes

DFARS Specialty Metals

Exempt

Export Control Classification Number (ECCN)

EAR99

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32 Products

Go/No-Go Helical Insert Threaded Plug Gauges with Handle

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.

Plug Gauges with Accuracy Certificate Traceable to NIST—Gauges with an accuracy certificate 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.

Plug Gauges with Calibration Certificate Traceable to NIST—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.

								Plug Gauges with Accuracy Certificate Traceable to NIST		Plug Gauges with Calibration Certificate Traceable to NIST
	Thread Size	Thread Type	Pitch Dia. Tolerance	Hardness	Material	Features	For Thread Fit		Each		Each
Class X Gauge



		2-56	UNC	-0.0002" to 0.0002"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N11	0000000	7941N28	0000000


		4-40	UNC	-0.0002" to 0.0002"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N12	000000	7941N29	000000
		6-32	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N13	000000	7941N31	000000
		8-32	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N14	000000	7941N32	000000
		10-24	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N15	000000	7941N33	000000
		10-32	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N16	000000	7941N34	000000
		1/4"-20	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N17	000000	7941N35	000000
		1/4"-28	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N18	000000	7941N36	000000
		5/16"-18	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N19	000000	7941N37	000000
		5/16"-24	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N21	000000	7941N38	000000
		3/8"-16	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N22	000000	7941N39	000000


		3/8"-24	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N23	000000	7941N41	000000
		1/2"-13	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N24	000000	7941N42	000000
		1/2"-20	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N25	000000	7941N43	000000
		5/8"-11	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N26	000000	7941N44	000000
		3/4"-10	UNC	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	7941N27	000000	7941N45	000000