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Thread Plug and Ring Gauge
A thread gauge checks whether a thread meets its specified size and form. A thread plug gauge inspects internal threads, and a thread ring gauge inspects external threads. GO and NO-GO members confirm the thread is within tolerance using a simple pass or fail check.
What is a thread gauge?
Thread gauges give a fast, reliable accept or reject decision. They check thread fit without measuring every dimension. A plug gauge screws into an internal thread; a ring gauge fits over an external thread.
Thread plug vs thread ring gauges
| Gauge | Inspects | GO result | NO-GO result |
|---|---|---|---|
| Thread plug gauge | Internal threads | Should screw in fully | Should not enter beyond allowance |
| Thread ring gauge | External threads | Should screw on fully | Should not pass beyond allowance |
How GO and NO-GO gauges work
The GO member should engage fully with a conforming thread. The NO-GO member should not engage beyond a small specified allowance. Together they confirm the thread is within tolerance without measuring individual dimensions.
Common thread forms
Thread gauges are available for metric, BSP, BSW, NPT and other common thread forms. Confirm the exact forms and sizes stocked from the live product listing below.
How to choose
Select by thread form, nominal size and tolerance class. Match the gauge to the drawing callout. Use plug gauges for internal threads and ring gauges for external threads. Contact BTSA to confirm availability for your specific thread form.
Frequently asked questions
What is a thread gauge used for?
It checks whether a thread meets its specified size and form using GO and NO-GO members.
What is the difference between a plug and ring thread gauge?
A plug gauge checks internal threads. A ring gauge checks external threads.
How do GO and NO-GO gauges work?
The GO member should engage fully. The NO-GO member should not, confirming the thread is in tolerance.
Which thread forms are covered?
Common forms include metric, BSP, BSW and NPT. Confirm availability from the live product listing.
Do thread gauges need calibration?
Yes. They are calibrated against traceable standards. Contact BTSA for calibration support.
