Spi 34-373-1 Double End Plug Thread Gage 12-28 2B

Product Description

The SPI 34-373-1 is a double-end plug thread gage used to verify internal thread conformance on machined or tapped holes. One end checks the Go condition to confirm the thread accepts a mating fastener; the opposite end checks the No-Go condition to confirm the thread does not exceed maximum material limits. Built from steel and traceable to NIST standards, this gage is suited for quality control and inspection on the shop floor or in the field. A handle is included. The gage weighs 1 pound and is ready to use out of the package.

This gage is intended for inspecting 12-28 unified national threads to a 2B tolerance class. The 2B classification covers standard commercial and industrial internal threads where a controlled fit is required. It is commonly used by machinists, quality inspectors, and maintenance technicians working with precision-threaded components in manufacturing, mechanical assembly, and equipment repair applications.

Key Features

• Double-end design with Go and No-Go members on a single tool for efficient thread inspection
• Thread size 12-28 for inspecting fine-pitch unified national threads
• 2B tolerance class for standard commercial internal thread verification
• Steel construction for durability in production and inspection environments
• NIST-traceable calibration included for documentation and compliance requirements
• Handle included — no separate purchase required

Compatibility

Designed for inspecting 12-28 internal threads to the 2B tolerance class per unified national thread standards.

Installation Notes

Thread gages are inspection tools used by machinists and quality technicians — no power tools or fastener torque is required. Clean the threaded hole and the gage members before use to prevent debris from affecting readings. The Go member should pass through the full thread length under hand pressure only; never force it. Store the gage in its case when not in use to protect the thread form and maintain calibration integrity.