Spi 23-149-8 Threaded Ring Gage 12-28 Class 2A Go No Go

Product Description

The SPI 23-149-8 is a double-ring threaded ring gage designed to verify external thread conformance on 12-28 unified thread form fasteners and components. It includes both a Go ring and a No Go ring in a single double-ring assembly, allowing technicians to confirm that a threaded part falls within the acceptable tolerance range for Class 2A fit. Manufactured from tool steel for dimensional stability and wear resistance, this gage is traceable to NIST standards, making it suitable for quality control environments where documented traceability is required. Machinists, quality inspectors, and tool room technicians use this gage as part of standard thread verification workflows.

This gage is used in manufacturing, machining, and inspection environments where 12-28 UNF external threads must be verified against Class 2A tolerances. Typical applications include incoming inspection of threaded fasteners, in-process thread verification on CNC-machined components, and final inspection before assembly. The double-ring format allows both Go and No Go checks without switching tools, streamlining the inspection process on the shop floor or in a dedicated quality lab.

Key Features

• Double-ring design includes both Go and No Go rings in one tool for complete Class 2A thread verification
• Calibrated to NIST standards with traceability certification included
• Tool steel construction provides durability and dimensional stability under repeated use
• Compact and lightweight at 0.118 pounds for easy handling during inspection
• Designed for 12-28 unified thread form external threads

Compatibility

Designed for verifying external threads with a 12-28 thread size and Class 2A thread classification per unified thread standards.

Installation Notes

Thread ring gages are precision measuring instruments and should be handled and stored with care to prevent damage to the ground bore. Before use, clean both the gage and the threaded workpiece to remove chips, oil, and debris that could affect the reading. Do not force the Go ring onto a thread that does not turn freely, as this indicates an out-of-tolerance condition. Periodic recalibration against setting plugs is recommended to maintain measurement accuracy over time.