Spi 34-255-0 Plug Thread Gage 1/4-28 6H No Go

Product Description

The SPI 34-255-0 is a single-end plug thread gage used to verify that a tapped or threaded hole does not exceed the maximum material condition for a 1/4-28 thread form. Manufactured from steel and classified to 6H tolerance, this No Go gage member is used in pass/fail inspection workflows to confirm that internal threads are within the upper limit of the tolerance band. When the No Go member fails to enter the threaded hole, the part passes inspection. This gage ships without a handle — a Size 1 handle is required for use and must be sourced separately. NIST traceability documentation is included, supporting quality and calibration records.

This gage is used in precision machining, manufacturing inspection, and quality control environments where internal thread verification is required to ANSI standards. It is suited for 1/4-28 UNF fine-pitch internal threads found in mechanical assemblies, instrumentation, and fastener applications. Machinists, quality technicians, and metrology personnel use this gage during in-process and final inspection to reject non-conforming threaded holes before assembly.

Key Features

• No Go member verifies that internal threads do not exceed the maximum material limit for 1/4-28 6H class
• Steel construction for durability and dimensional stability under repeated use
• 6H classification meets ANSI tolerance standards for general-purpose internal threads
• NIST traceability certification included for calibration and quality system compliance
• Single-end design for dedicated No Go inspection use
• Size 1 handle required — not included, must be ordered separately

Compatibility

Designed for inspection of 1/4-28 UNF internal threads classified to 6H tolerance per ANSI standards. Accepts a standard Size 1 plug gage handle, which is not included with this gage.

Installation Notes

This gage is installed into a compatible Size 1 handle before use — do not attempt to operate the gage without a properly fitted handle. Always clean the threaded hole and the gage member before gauging to prevent debris from causing false rejects. Store the gage in its protective case when not in use to preserve the ground finish and dimensional accuracy. Periodic recalibration against NIST-traceable standards is recommended to maintain inspection integrity.