Spi 34-430-9 Double End Plug Thread Gage 1-8 3B

Product Description

The SPI 34-430-9 is a double-end plug thread gage used to verify internal thread dimensions to 1-8 UN thread specification at 3B tolerance class. One end checks the Go condition, confirming threads fall within minimum material limits. The other end checks the No Go condition, confirming threads do not exceed maximum material limits. The gage is constructed of steel and ships with a size 4 handle included. A NIST traceability certification is included, making it suitable for quality-control environments where documentation of measurement standards is required. Machinists, quality inspectors, and tool-room technicians use this type of gage in production and inspection workflows.

This gage is applied wherever 1-8 coarse unified national thread forms must be verified in tapped holes. Typical applications include incoming inspection of threaded components, in-process checks on machined parts, and final inspection before assembly. The 3B classification indicates a standard commercial tolerance class for internal threads, commonly specified for general-purpose fastener applications in both industrial and mechanical assemblies. The double-end design keeps both Go and No Go members on a single handle, reducing changeover time during inspection runs.

Key Features

• Go and No Go ends on a single double-end gage for efficient thread verification
• 1-8 UN thread size for coarse unified national thread inspection
• 3B tolerance class for standard commercial internal thread applications
• Steel construction for durability in shop and inspection environments
• Size 4 handle included — ready to use out of the box
• NIST traceability certification included for quality documentation requirements

Compatibility

Designed for inspection of internal threads conforming to 1-8 UN unified national coarse thread form at 3B tolerance class.

Installation Notes

Plug thread gages are used by quality inspectors and machinists — not installed in a system, but handled and stored with care to preserve gage accuracy. Keep the gage clean and lightly oiled when not in use to prevent corrosion on the steel members. Do not force the No Go end into a threaded hole; it should not enter a correctly formed thread by hand pressure alone. Store separately from cutting tools to avoid contact damage to the thread form.