Spi 34-400-2 Plug Thread Gage 1/2-13 3B Double End

Product Description

The SPI 34-400-2 is a double-end plug thread gage used to verify internal thread quality on 1/2-13 UNC threaded holes. One end checks the Go condition, confirming the thread accepts a mating fastener. The opposite end checks the No Go condition, confirming the thread is not oversized or out of tolerance. The gage is manufactured from steel and is classified to the 3B tolerance class, making it suitable for general-purpose inch-series threaded fastener applications. A handle is included, and a Traceability Certification traceable to NIST is provided with each unit. Machinists, quality control technicians, and precision fabricators use this gage in production and inspection environments.

This plug thread gage is used in machine shops, manufacturing facilities, and inspection departments wherever 1/2-13 UNC tapped holes must be verified against NIST-traceable standards. The 3B class designation covers the most common commercial and industrial threaded hole tolerance range. The double-end design puts both Go and No Go gages on a single handle, reducing tool changeover time during high-volume thread inspection. The included handle is size 2, compatible with standard plug gage handle systems.

Key Features

• Verifies 1/2-13 UNC internal threads to 3B tolerance class
• Double-end design combines Go and No Go gages on one handle
• NIST-traceable traceability certification included
• Steel construction for durability in production inspection use
• Size 2 handle included — no separate handle purchase required

Compatibility

Designed for use with standard size 2 plug gage handles. Suitable for inspecting 1/2-13 UNC tapped holes classified to 3B tolerance per ASME/ANSI inch-series thread standards.

Installation Notes

Thread gages are inspection tools and do not require installation in the traditional sense. Store gages in a clean, dry environment and handle them with care to avoid surface damage that could affect accuracy. Clean the gage and the part being inspected before use to prevent debris from producing false readings. Re-certification intervals should follow your facility quality plan and applicable metrology standards.