What is a thread ring gauge used for?

It is used to verify the dimensional accuracy of internal threads by manual testing without force.

What does NPT 1/4 x 18 mean?

NPT (National Pipe Thread) refers to an American tapered pipe thread with a 60° flank angle and 18 threads per inch for a 1/4 inch nominal size.

Which standard applies to this gauge?

The gauge is manufactured according to ANSI/ASME B 1.20.1, defining the dimensions and tolerances of tapered pipe threads.

Is calibration available?

Yes, VÖLKEL offers an optional factory calibration certificate issued by an independent laboratory using IAC thread scanners.

How should the inspection be performed?

Manually screw the gauge into the thread at 20 °C without tools. It should fit smoothly over the defined length; otherwise, the thread is out of tolerance.

VÖLKEL precision thread limit ring gauge NPT with go and no-go sides for accurate pipe thread inspection

Thread gauge calibration certificate showing measurement data, tolerances, and graphical analysis.

NPT (tapered pipe thread)

Precision Thread Ring Gauge - NPT 1/4 x 18

Name: VÖLKEL Precision Thread Ring Gauge - NPT 1/4 x 18
Brand: VÖLKEL
SKU: 16486
Price: 270.00 EUR
Availability: InStock

Item no. 16486

€270.00

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 Thread Ring Gauge – NPT 1/4 x 18

The VÖLKEL Precision Thread Ring Gauge NPT 1/4 x 18 is designed for manual inspection of tapered pipe threads in accordance with ANSI/ASME B 1.20.1. It ensures that internal threads meet the required dimensional accuracy at a reference temperature of 20 °C. A factory calibration certificate is available on request.

Application

Manual inspection of internal NPT threads
Quality control in production, incoming inspection, and maintenance
Testing without auxiliary tools or force
Reference temperature for parts and gauges: 20 °C

Step-by-Step Inspection Guide

Conditioning: Ensure part and gauge are acclimatized to 20 °C.
Cleaning: Remove debris and oil from both thread and gauge.
Alignment: Position the gauge perpendicular to the thread axis.
Manual Testing: Screw in the gauge by hand without tools. The GO side should fit easily up to the L1 mark (if present).
Evaluation: If it does not fit smoothly, the thread is out of tolerance. The NO-GO side, if applicable, must not screw in.
Documentation: Record the result and request calibration if required.

Technical Data

Standard	ANSI / ASME B 1.20.1
Thread Type	NPT 1/4 x 18
Article Number	16486
EAN	4022835164869
Reference Temperature	20 °C
Calibration	Optional factory calibration certificate

FAQ

How tight should I screw the gauge?
Only by hand – without any tools or extensions.

What does “GO” mean?
The GO ring must screw in smoothly; if it doesn’t, the thread is out of tolerance. NO-GO rings must not engage.

What is the L1 mark for?
It indicates the correct hand-tight engagement point for NPT thread inspection.

How often should I recalibrate?
Depending on usage and quality standards; VÖLKEL provides calibration services on request.

Which cleaning agents should be used?
Use a clean lint-free cloth or alcohol; avoid aggressive solvents or abrasives.

Need help with selection or calibration? Contact our team via the contact form.

Additional information

Type of thread	american tapered pipe thread, taper 1:16
Standard	ANSI /ASME B 1.20.1
Size	NPT 1/4 x 18
EAN	4022835164869
Item number	16486
Gauge dimension	ANSI /ASME B 1.20.1
Thread standard	ANSI B1.20.1