Spi 34-259-2 Plug Thread Gage 5/16-18 6H Single End Go

Product Description

The SPI 34-259-2 is a single-end Go plug thread gage designed to verify the minimum material condition of internal threads. It checks that a 5/16-18 UNC threaded hole will accept a mating fastener within the 6H tolerance class. Manufactured from steel for dimensional stability and wear resistance, this gage is NIST-traceable and conforms to ANSI standards. A size 1 handle is required for use but is not included with this gage. It is used by machinists, quality control inspectors, and tradespeople who need to confirm thread acceptability on production parts, fabricated assemblies, or field-installed components.

This gage is suited for inspection of 5/16-18 internal threads in manufacturing, maintenance, and repair environments. It is commonly used in metalworking shops, fabrication facilities, and industrial maintenance settings where thread quality must be verified before assembly. The 6H classification makes it appropriate for general-purpose commercial thread inspection. Because a handle is not included, users must supply a compatible size 1 plug gage handle to operate this gage correctly.

Key Features

• Go member only — verifies minimum material condition for 5/16-18 internal threads
• 6H tolerance class for general-purpose commercial thread applications
• Steel construction provides durability and dimensional stability under repeated use
• NIST-traceable certification included for quality and audit compliance
• Conforms to ANSI standards
• Single-end design; requires a size 1 handle (sold separately)

Compatibility

Designed for use with standard size 1 plug gage handles to inspect 5/16-18 UNC internal threads to 6H tolerance class per ANSI specifications.

Installation Notes

This gage is installed into a compatible size 1 plug gage handle before use. Inspect the gage and handle for damage or contamination before each measurement session. Apply light machine oil or gage lubricant to extend gage life and improve measurement consistency. Do not force the Go member through a thread — resistance indicates a thread that may be out of tolerance.