Spi 34-399-6 Plug Thread Gage 1/2-13 2B Double End

Product Description

The SPI 34-399-6 is a double-end plug thread gage designed to verify 1/2-13 UNC internal threads to a 2B tolerance class. One end carries the Go member to confirm the thread will accept a mating fastener; the opposite end carries the No Go member to confirm the thread has not been cut oversize. The gage is machined from steel for wear resistance and dimensional stability. A size 2 handle is included. The tool ships with a traceability certification traceable to NIST standards, supporting documented quality control programs in manufacturing, maintenance, and inspection environments.

The 34-399-6 is used in machine shops, production floors, and field maintenance settings wherever 1/2-13 tapped holes must be verified before assembly. Typical applications include confirming thread quality in structural fastener holes, pipe-fitting flanges, equipment frames, and mechanical sub-assemblies. Machinists, quality inspectors, and maintenance technicians reach for this gage when a visual check is not sufficient and a pass/fail thread verification is required to meet print or specification tolerances.

Key Features

• Double-end design provides Go and No Go members in a single tool
• Calibrated to 1/2-13 UNC thread form at 2B tolerance class
• Steel construction for durability and dimensional stability under repeated use
• Size 2 handle included — no separate handle purchase required
• NIST-traceable certification included to support quality documentation and audit requirements

Compatibility

Designed to inspect 1/2-13 UNC internal threads cut to a 2B tolerance class in any material or application where that thread form is specified.

Installation Notes

Thread gages are inspection tools, not cutting tools — they should be hand-turned only and never forced. Keep the gage clean and lightly oiled when not in use to prevent corrosion and maintain calibration accuracy. Periodic recalibration against a reference standard is recommended to ensure continued measurement reliability, especially in high-cycle inspection environments. Store the gage in its case or a protected location to prevent contact damage to the thread members.