Spi 34-439-0 Pipe Thread Plug Gage 1-11-1/2 Npt Class L-1

Product Description

The SPI 34-439-0 is a tapered pipe thread plug gage used to verify the accuracy of internal NPT pipe threads to ANSI B1.20.1 standards. It is a single-end gage configured for the 1-11-1/2 thread size, meaning a 1-inch nominal pipe with 11.5 threads per inch. The Class L-1 designation defines the engagement length and tolerance limits applied during inspection. A NIST Traceability Certificate is included, supporting quality-system documentation requirements in shop, field, and metrology lab environments. This gage is handled by machinists, pipe fabricators, quality control inspectors, and trade professionals who require verified thread conformance before assembly.

This gage is suited for inspecting internally threaded pipe fittings, valves, manifolds, and threaded port connections across HVAC, plumbing, gas distribution, and industrial piping applications. The tapered NPT profile matches the self-sealing taper geometry specified by ANSI B1.20.1. It is used wherever a threaded pipe joint must meet pressure-rated or leak-free assembly requirements prior to installation. Handle Size 5 is included with the gage, providing a grip appropriate for the 1-11-1/2 thread diameter during manual inspection.

Key Features

• Tapered NPT thread form per ANSI B1.20.1 for standardized pipe thread inspection
• Class L-1 tolerance class defines engagement length for go-gage acceptance criteria
• Single-end configuration with Handle Size 5 included
• NIST Traceability Certificate included for quality-system and audit compliance
• Thread size 1-11-1/2 covers 1-inch nominal pipe at 11.5 threads per inch

Compatibility

Designed for inspection of internal tapered NPT pipe threads at the 1-11-1/2 thread size, conforming to ANSI B1.20.1 and NIST traceability standards. Applicable wherever Class L-1 NPT thread acceptance criteria are specified.

Installation Notes

Thread plug gages are inspection tools and should be handled by qualified machinists or QC personnel familiar with ANSI B1.20.1 acceptance procedures. Apply thread gage lubricant or light oil before use to protect the gage and the workpiece threads. Do not force the gage into the thread; engagement should be hand-tight only to the L-1 notch reference. Store the gage in its protective case when not in use to prevent damage to the precision thread form.