Taper Pipe Plug Gages
A taper pipe plug gage inspects an internal tapered pipe thread — the threaded hole a fitting screws into. Because a taper thread seals by wedging rather than by bottoming out, it cannot be accepted on diameter alone: the gage establishes where the thread stands relative to the gaging notch or step, and that standoff is the measurement. WESTport manufactures taper pipe plug gages for NPT, NPTF and ANPT thread forms, precision ground and hand lapped, and certifies every one in our own climate-controlled, ISO/IEC 17025 accredited laboratory with NIST-traceable documentation.
The WESTport taper pipe plug gage line
Each gage below is a single product covering the full size range and every step type in that form. Select size and step type on the product page.
- NPT Taper Pipe Plug Gage. L1 plug gages for general-purpose American National Standard Taper Pipe internal threads, checking functional size and hand-tight engagement across the standard pipe sizes from 1/16-27 upward.
- NPTF Taper Pipe Plug Gage. The full dryseal family in one product — L1 for hand-tight engagement, L3 for wrench engagement and taper, and the 6-step for crest and root truncation. NPTF threads seal without compound, so the truncation check is not optional.
- ANPT Thread Plug Gage. Aeronautical National Form Taper Pipe gages manufactured to SAE AS71051, in L-1, L-3 and 6-step, for pipe threads in aerospace fluid and pneumatic systems.
What taper pipe gages inspect
Which gage checks what
A taper pipe thread is not accepted on a single check. Each gage in the family answers a different question, which is why they are ordered together.
| Gage | What it checks | Why it matters |
|---|---|---|
| L1 | Functional size — hand-tight engagement | Confirms the thread will start and seat to the correct standoff |
| L3 (plug) / L2 (ring) | Wrench engagement and taper | Confirms enough usable thread remains past hand-tight to torque the joint |
| 6-step | Crest and root truncation — the thread profile itself | Required on NPTF dryseal threads, where crest-to-root contact makes the seal |
NPT, NPTF and ANPT
NPT is the general-purpose American taper pipe thread; it seals on the flanks and normally needs a sealant. NPTF is the dryseal form — the crests and roots interfere on assembly to seal without compound, which is why NPTF work requires the 6-step truncation check that NPT does not. ANPT is the aeronautical form manufactured to SAE AS71051, dimensionally NPT but held to tighter limits and inspection requirements for aerospace fluid systems.
What comes with every gage
- Certificate of Accuracy, NIST traceable. Certified in our own climate-controlled, ISO/IEC 17025 accredited laboratory.
- Long form certification available. Full dimensional data where your quality system requires it.
- In-house calibration and recertification. Send gages back to us for periodic recert rather than replacing them.
- Made in the USA. Precision ground and hand lapped for accuracy, finish and wear life.
| PART# | PRODUCT NAME | SIZE | TPI | PRICE | SALE PRICE |
