Spi 34-382-2 Plug Thread Gage 5/16-18 3B Double End

Product Description

The SPI 34-382-2 is a double-end plug thread gage designed to inspect 5/16-18 UNC internal threads to Class 3B tolerance. One end carries the Go member; the opposite end carries the No Go member. The gage confirms that a threaded hole falls within the specified pitch diameter limits — Go must enter freely, No Go must not. A handle is included. This tool is used by machinists, quality inspectors, and tradespeople verifying threaded fastener holes in steel fabrication, mechanical assemblies, and precision maintenance work. Steel construction provides durability under repeated use in shop environments.

The 34-382-2 is suited for incoming inspection, in-process quality checks, and final verification of 5/16-18 tapped holes in Class 3B fit applications. Class 3B is the standard tight-tolerance fit used in most structural and mechanical fastener applications where close thread engagement is required. The included handle is size 1, appropriate for the 5/16-18 thread range. This gage is a common tool in manufacturing, MRO, and mechanical contracting shops where thread quality must be documented and verified.

Key Features

• Double-end design: Go and No Go members on a single gage body with size 1 handle
• Inspects 5/16-18 UNC internal threads to Class 3B tolerance limits
• Steel construction for durability and dimensional stability under shop use
• NIST traceability certification included for documented quality programs
• Handle included — ready to use without additional accessories

Compatibility

Designed for inspection of 5/16-18 UNC internally threaded components requiring Class 3B fit verification. Compatible with standard size 1 plug gage handles.

Installation Notes

Thread gages are hand tools requiring no installation. Apply a light film of clean oil to the gage members before use to reduce wear and prevent galling against the workpiece threads. Do not force the Go end — if it does not pass freely, the thread does not conform. Store gages in their case away from other metal tools to prevent contact damage to the precision ground surfaces. Periodic re-calibration against NIST-traceable standards is recommended to maintain measurement integrity.