What does UNC 3/8 x 16 mean?

UNC stands for Unified National Coarse, an inch-based thread form from the Unified Thread Standard. 3/8 refers to the nominal diameter in inches, and 16 is the number of threads per inch (TPI).

What is tolerance class 2A?

2A is the standard tolerance class for external threads in the Unified system. It provides functional clearance for general-purpose production and matches with 2B internal threads.

What standards apply to this thread gauge?

The geometry follows ANSI B1.1 (Unified Inch Screw Threads), while the gauge design and tolerances follow ANSI B1.2 (Gauges and Gaging).

How should the gauge be used correctly?

The GO ring gauge must screw onto the thread entirely by hand, without the use of excessive force. If it cannot, the workpiece is considered out of tolerance (scrap).

Is calibration available?

Yes, VÖLKEL can issue a factory calibration certificate upon request. Calibration is performed in an independent lab using IAC thread scanners according to applicable standards.

What does UNC 3/8 x 16 mean?

UNC stands for Unified National Coarse, an inch-based thread form from the Unified Thread Standard. 3/8 refers to the nominal diameter in inches, and 16 is the number of threads per inch (TPI).

What is tolerance class 2A?

2A is the standard tolerance class for external threads in the Unified system. It provides functional clearance for general-purpose production and matches with 2B internal threads.

What standards apply to this thread gauge?

The geometry follows ANSI B1.1 (Unified Inch Screw Threads), while the gauge design and tolerances follow ANSI B1.2 (Gauges and Gaging).

How should the gauge be used correctly?

The GO ring gauge must screw onto the thread entirely by hand, without the use of excessive force. If it cannot, the workpiece is considered out of tolerance (scrap).

Is calibration available?

Yes, VÖLKEL can issue a factory calibration certificate upon request. Calibration is performed in an independent lab using IAC thread scanners according to applicable standards.

VÖLKEL precision thread go ring gauge with knurled edge for internal thread inspection.

Close-up of a VÖLKEL precision thread ring gauge during GO inspection – high-accuracy tool for testing internal thread tolerances (6g), made in Germany.

UNC (Unified coarse)

Precision GO Thread Ring Gauge (Tol. 2A) - UNC 3/8 x 16

Name: VÖLKEL Precision GO Thread Ring Gauge (Tol. 2A) - UNC 3/8 x 16
Brand: VÖLKEL
SKU: 16300
Price: 54.00 EUR
Availability: InStock

Item no. 16300

€54.00

in stock - more than 10 pieces available

VÖLKEL delivers exclusively to specialized dealers. Online you can buy VÖLKEL products here.

The prices are in Euro plus VAT and shipping, insurance and packaging costs.

Application

VÖLKEL Precision GO Thread Ring Gauge (Tol. 2A) – UNC 3/8 x 16

The VÖLKEL Precision GO Thread Ring Gauge in UNC 3/8 x 16 (tolerance class 2A) enables quick, accurate, and reliable verification of external thread accuracy. Based on ANSI B1.1 (Unified Inch Screw Threads) and ANSI B1.2 (Gauges & Gaging). Reference temperature: 20 °C. Optional factory calibration certificate available on request.

Application & Benefits

Quick verification of external thread dimensions per UNC 3/8-16
Easy to use – no special metrology skills required
High precision and repeatable results
Suitable for any production method (turning, rolling, milling, etc.)
Optional factory calibration certificate; calibrated in an independent laboratory

Testing note: The gauge must fully screw onto the thread by hand at 20 °C without force. Otherwise, the part is out of tolerance.

UNC, ANSI B1.1 & ANSI B1.2 Explained

UNC (Unified National Coarse): Inch-based coarse thread form within the Unified Thread Standard, e.g. 3/8-16 (diameter / threads per inch).
ANSI B1.1: Defines geometry, tolerances, and classes (1A/2A/3A for external, 1B/2B/3B for internal threads).
ANSI B1.2: Defines gauge dimensions and inspection principles for Unified threads (GO/NO-GO gauges).
Tolerance Class 2A: Standard production quality with controlled clearance; pairs with 2B internal threads.

Technical Details

Thread	UNC 3/8 x 16
Tolerance Class	2A (External thread)
Standard	ANSI B 1.1
Gauge Dimensions	ANSI B 1.2
Reference Temperature	20 °C
Item Number	16300
EAN	4022835163008
Calibration	Optional factory certificate, calibrated on IAC thread scanners
Delivery	1× Precision GO Thread Ring Gauge UNC 3/8-16, Tol. 2A

Step-by-Step Testing Guide

1. Preparation: Clean and deburr the external thread; stabilize the environment to 20 °C.
2. Engagement: Align the gauge squarely with the thread start.
3. Testing: Screw the gauge manually over the entire thread without force.
4. Evaluation: Full manual engagement = OK. Resistance or incomplete travel = Reject.
5. Documentation: Record inspection results and gauge identification if required.

FAQ

Why is the reference temperature 20 °C?
Thermal expansion affects dimensions. 20 °C ensures consistent and comparable measurements.

What is the difference between 2A and 3A?
3A provides a tighter fit with less clearance, used for precision assemblies. 2A is standard for general production.

Can I order it calibrated?
Yes, a factory calibration certificate can be issued upon request.

When is a part considered scrap?
If the GO gauge cannot be fully screwed by hand without force, the thread is out of tolerance.

Do I need extra measuring tools?
No, for GO testing the ring gauge is sufficient. For full dimensional analysis, dedicated measuring equipment is required.

Questions about standards, selection or calibration? Our team will be glad to assist you – please use the contact form.

Additional information

Type of thread	Unified coarse thread
Standard	ANSI B 1.1
Tolerance	2A
Size	UNC 3/8 x 16
EAN	4022835163008
Item number	16300
Gauge dimension	ANSI B 1.2
Thread standard	ANSI B 1.1