Spi 34-390-5 Plug Thread Gage 3/8-24 3B Double End Go No Go

Product Description

The SPI 34-390-5 is a double-end plug thread gage designed to verify internal thread quality on 3/8-24 UNF threads to the 3B tolerance class. One end carries the Go member and the other carries the No Go member, allowing a technician to confirm both the minimum and maximum thread limits in a single tool. The gage ships with a size 2 handle and includes an NIST-traceable traceability certification, making it suitable for use on the shop floor and in documented quality control processes. The steel construction holds dimensional stability under repeated use in production or inspection environments.

This gage is used wherever 3/8-24 internal threads must be verified to 3B class tolerances — a common requirement in precision machining, aerospace, automotive, and general industrial assembly. Inspectors and machinists use it to accept or reject tapped holes before assemblies move to the next stage of production. The included handle and NIST certification mean the tool is ready for immediate use without additional setup or documentation procurement.

Key Features

• Double-end design combines Go and No Go gages into one tool for efficient thread inspection
• Calibrated to 3B class tolerance for 3/8-24 UNF internal threads
• NIST-traceable traceability certification included for quality documentation requirements
• Size 2 handle included — no separate handle purchase required
• Steel construction for durability and dimensional stability in production environments

Compatibility

Designed for inspection of 3/8-24 UNF internal threads manufactured to the 3B tolerance class. Suitable for use with standard size 2 plug gage handles.

Installation Notes

Plug thread gages are used by machinists and quality control inspectors — no installation in a system is required. Store the gage in its case when not in use to protect the thread members from damage and contamination. Do not force the No Go member into a thread; if it enters, the part is out of tolerance and should be rejected per the applicable quality standard. Periodic re-calibration against NIST-traceable masters is recommended to maintain measurement integrity.