Spi 34-309-5 Plug Thread Gage 5/8-18 3B No Go

Product Description

The SPI 34-309-5 is a single-end, No Go plug thread gage machined from steel and designed to verify internal thread conformance to a 5/8-18 UNF thread specification at a 3B tolerance class. No Go gages confirm that a threaded hole has not been cut oversize or out of tolerance, which would cause joint failure or leakage under load. This gage is used in quality control, incoming inspection, and production floor verification by machinists, quality technicians, and precision trade professionals. The gage body is sized for a Size 3 handle, sold separately. A NIST traceability certification is included, supporting documentation requirements in calibrated shop environments.

This gage is suited for inspecting 5/8-18 UNF threaded holes in components across mechanical, plumbing, HVAC, and industrial assembly applications. It is particularly useful where fine-thread fastener joints require tight tolerance verification. The single-end configuration keeps the tool compact and dedicated to the No Go function, reducing the chance of misapplication during high-volume inspection cycles. Technicians working to documented quality plans or ISO-compliant procedures will find the included NIST traceability certificate directly usable for gage records.

Key Features

• No Go function verifies internal threads are not oversized beyond 3B class tolerance
• 5/8-18 UNF thread size for fine-pitch internal thread inspection
• Steel construction for durability and dimensional stability in shop environments
• Single-end design dedicated to one function, reducing inspection error
• NIST traceability certification included for calibration record compliance
• Sized for a Size 3 handle (handle not included)

Compatibility

Designed for use with a Size 3 plug gage handle, sold separately. Intended for inspection of 5/8-18 UNF internal threads to ANSI/ASME 3B tolerance class standards.

Installation Notes

This gage is handled and used by quality control technicians and machinists — no power tools or utilities need to be shut down for gage use. Insert the gage by hand into the threaded hole without forcing; a properly toleranced No Go gage should not thread fully into a conforming part. Never apply torque tools or excessive force to a thread gage, as this will damage the gage and invalidate the inspection result. Store the gage in its protective case and re-certify per your facility calibration schedule to maintain NIST traceability.