Spi 34-441-6 Pipe Thread Plug Gage 1-1/2-11-1/2 Npt L-1

Product Description

The SPI 34-441-6 is a tapered pipe thread plug gage designed to verify the accuracy of internal NPT threads to Class L-1 tolerance specifications. Built to ANSI B1.20.1 standards, this single-end gage checks 1-1/2-11-1/2 NPT threads — a common size in plumbing, HVAC piping, and industrial pipe assemblies. It ships with a NIST Traceability Certificate, making it suitable for quality control programs that require documented measurement standards. Handle Size 5 provides a comfortable grip for controlled engagement during inspection. Plumbers, pipefitters, and QC technicians use this gage to confirm that threaded fittings and pipe connections will seal properly before assembly.

This gage is used in field inspection, shop floor quality control, and incoming material verification for piping systems that use NPT tapered threads. The 1-1/2-11-1/2 thread size appears frequently in commercial plumbing headers, HVAC refrigerant piping manifolds, compressed air distribution systems, and industrial fluid handling lines. It is suited for both fabrication shops and service environments where thread integrity directly affects system pressure performance.

Key Features

• Checks 1-1/2-11-1/2 NPT internal threads to Class L-1 tolerance per ANSI B1.20.1
• Tapered thread form matches NPT pipe thread geometry for accurate engagement verification
• Single-end configuration with Handle Size 5 for controlled, repeatable gage insertion
• Includes NIST Traceability Certificate for compliance with quality management and documentation requirements
• Conforms to ANSI B1.20.1 and NIST standards for pipe thread gaging

Compatibility

Designed for use with internal NPT tapered pipe threads sized 1-1/2-11-1/2, conforming to ANSI B1.20.1. Compatible with standard NPT-L1 thread gaging applications in plumbing, pipefitting, and industrial piping inspection.

Installation Notes

Thread plug gages are inspection tools and are not permanently installed. Engage the gage by hand — never force it with a wrench or power tool, as this will damage the gage threads and invalidate the measurement. Before gaging, ensure the workpiece threads are clean and free of chips, burrs, or lubricant buildup that could affect readings. Gages should be stored in a protective case and recalibrated periodically to maintain traceability.