Spi 34-388-9 Plug Thread Gage 3/8-16 3B Double End Go No Go

Product Description

The SPI 34-388-9 is a double-end plug thread gage used to verify internal thread compliance on 3/8-16 UNC fastener holes. One end carries the Go member; the opposite end carries the No Go member. The Go end must pass fully through an acceptable thread, while the No Go end must not enter beyond two turns. Manufactured from steel and supplied with a size 2 handle, this gage is traceable to NIST standards, making it suitable for quality control work on production floors, in machine shops, and in field inspection environments. Machinists, QC inspectors, and precision tradespeople are the primary users.

This gage is used wherever 3/8-16 internal threads must be verified for conformance to Class 3B tolerance requirements. Class 3B designates a tight-tolerance fit, commonly specified in aerospace, automotive, and industrial fastener applications where thread engagement precision is critical. The double-end configuration consolidates Go and No Go inspection into a single tool, reducing changeover time during high-volume inspection runs. A handle is included, so no separate handle purchase is required.

Key Features

• Double-end design combines Go and No Go members in one tool
• Class 3B tolerance rating for tight-fit internal thread inspection
• NIST-traceable calibration certification included
• Steel construction for durability and dimensional stability
• Size 2 handle included — ready to use out of the package
• Conforms to NIST standards for thread gage measurement

Compatibility

Designed for inspection of 3/8-16 UNC internal threads to Class 3B tolerance specifications. Confirm thread form, pitch, and tolerance class before use.

Installation Notes

Thread gages do not require installation in a mechanical system, but proper handling is essential to maintain calibration accuracy. Store the gage in its case when not in use and avoid dropping or contacting the gage members with abrasive surfaces. Clean threads in the workpiece before gaging to prevent debris from causing false rejections. Recalibrate or re-certify the gage at intervals specified by your quality management program or applicable inspection standards.