Spi 34-423-4 Plug Thread Gage 7/8-9 2B Double End

Product Description

The SPI 34-423-4 is a double-end plug thread gage used to verify internal thread quality on machined parts with a 7/8-9 thread form. One end carries the Go member, which confirms the thread will accept a mating fastener across the full tolerance zone. The opposite end carries the No Go member, which confirms the thread has not been cut oversize. The gage is manufactured from steel and conforms to 2B classification tolerances. A size 4 handle is included. A NIST traceability certification ships with the unit, supporting quality-system documentation requirements in manufacturing and inspection environments.

This gage is used in production inspection, incoming quality control, and maintenance repair operations wherever 7/8-9 UNC internal threads are produced or verified. Machinists, quality technicians, and toolroom inspectors rely on double-end plug gages like the 34-423-4 to provide fast, definitive pass-fail decisions at the machine or inspection bench without the need for additional measuring instruments. It is well suited to both job-shop and high-volume manufacturing settings.

Key Features

• Double-end design combines Go and No Go members in a single tool for efficient thread verification
• Calibrated to 7/8-9 thread form at 2B class tolerance
• Steel construction provides durability in production environments
• Size 4 handle included — no separate handle purchase required
• NIST traceability certification included for quality-system compliance

Compatibility

Designed for use on internal threads with a 7/8-9 thread size and 2B class tolerance designation. Suitable for use in any inspection process where NIST-traceable thread verification is required.

Installation Notes

Thread plug gages are inspection tools, not cutting tools — they must never be forced into a thread. Apply the Go member by hand; it should enter the full length of the thread under finger pressure only. If the No Go member enters more than two turns, the thread is out of tolerance. Store gages in a clean, dry environment and recalibrate at intervals appropriate to usage frequency and your quality management system requirements.