Spi 34-398-8 Plug Thread Gage 7/16-28 3B Go No Go

Product Description

The SPI 34-398-8 is a double-end plug thread gage used to verify internal thread conformance to 7/16-28 thread specifications at 3B class tolerance. One end is the Go member; the other is the No Go member. The Go end must pass fully through a conforming threaded hole. The No Go end must not enter beyond the first turn. Handle is included. The gage is made from steel and ships with NIST traceability certification, making it suitable for use in quality-control environments where documented standards compliance is required. Machinists, tool-and-die technicians, and QC inspectors use this type of gage for incoming inspection, in-process verification, and final acceptance of threaded bores.

This gage is designed for checking 7/16-28 unified national fine (UNF) internal threads to 3B class tolerances. The 3B classification defines a standard commercial tolerance range widely used in general-purpose mechanical assemblies. A handle size 2 is included, which is the standard handle diameter for gages in this thread-size range. This tool is appropriate for use in machine shops, manufacturing facilities, and quality labs that require NIST-traceable inspection tooling.

Key Features

• Double-end design with Go and No Go members on a single gage body
• 7/16-28 thread size for unified national fine thread inspection
• 3B class tolerance for standard commercial-fit verification
• Steel construction for durability and dimensional stability
• Includes handle size 2 — no separate purchase required
• NIST traceability certification included for documented quality programs

Compatibility

Designed for inspection of 7/16-28 internal threads manufactured to 3B class tolerance per NIST-recognized standards.

Installation Notes

Thread gages require no installation. Store the gage in its case when not in use to protect the gage members from damage or contamination. Apply a light coat of clean instrument oil before and after use to prevent corrosion on the steel members. Calibration interval should be established based on frequency of use and the quality program requirements of the facility.