Spi 23-128-2 Thread Plug Gage 4-40 Go No Go Class 2A

Product Description

The SPI 23-128-2 is a truncated taperlock thread plug gage used to verify the accuracy of internal 4-40 UNC threads. It includes both Go and No Go members, allowing technicians to confirm that a tapped hole falls within Class 2A thread tolerance limits in a single tool set. The Go member checks that the thread will accept a mating fastener, while the No Go member confirms the thread has not been cut oversized. Constructed from tool steel, this gage is built for repeated use in production and inspection environments where thread quality control is critical.

This gage is appropriate for use in precision machining, assembly inspection, and quality control operations where 4-40 UNC threaded holes must meet Class 2A tolerance standards. It is commonly used by machinists, tool and die technicians, and quality assurance inspectors working with small-diameter fastener applications in both commercial and industrial settings.

Key Features

• Go and No Go members included for complete Class 2A thread verification in one set
• Truncated taperlock design for secure, repeatable handle engagement
• Sized for 4-40 UNC internal threads
• Tool steel construction for wear resistance and dimensional stability
• 5.75 inches in overall length with 0.75 inch width

Compatibility

Designed for inspection and verification of 4-40 UNC internally threaded components requiring Class 2A thread fit tolerance.

Installation Notes

Thread plug gages are used by quality control inspectors and machinists and require no permanent installation. Handle the gage carefully to avoid drops or impacts that can alter calibration. Clean threads being inspected before use to prevent debris from affecting gage readings. Store in a protective case when not in use to preserve dimensional accuracy.