Spi 23-151-4 Threaded Ring Gage 1/4-20 Class 2A Go No Go

Product Description

The SPI 23-151-4 is a double-ring threaded ring gage set used to inspect external threads for dimensional conformance. It includes both a Go ring and a No Go ring, allowing technicians to verify that a threaded workpiece falls within the accepted tolerance range for 1/4-20 thread at Class 2A fit. Machined from tool steel, the gage delivers the hardness and wear resistance needed for repeated use in production and inspection environments. NIST traceability is included, supporting quality systems that require documented calibration standards. This gage is used by machinists, quality control inspectors, and toolroom personnel.

This gage is suited for incoming inspection, in-process thread verification, and final quality checks on 1/4-20 externally threaded fasteners and components. The Class 2A classification covers the standard commercial and industrial tolerance class for unified inch screw threads, making this gage appropriate for a wide range of general-purpose manufacturing applications. Its compact size allows for easy bench use or deployment at a workstation.

Key Features

• Go and No Go rings included in a single double-ring gage for complete Class 2A thread inspection
• Machined from tool steel for durability and long service life under regular use
• NIST traceability certification included to support ISO and other quality management documentation requirements
• Conforms to NIST standards for thread gage accuracy
• Compact form factor fits standard bench inspection setups

Compatibility

Designed for inspection of external 1/4-20 unified coarse (UNC) threads to Class 2A tolerance specifications.

Installation Notes

Threaded ring gages are used by quality control inspectors and machinists and require no installation. Store gages in a clean, dry environment away from chips and contaminants to preserve calibration. Handle with care to avoid dropping, which can alter gage geometry and invalidate calibration. Periodic re-calibration against NIST-traceable masters is recommended per your facility quality program.