Spi 23-206-6 Thread Plug Gage 1-8 Unc Go No Go

Product Description

The SPI 23-206-6 is a truncated taperlock thread plug gage designed to verify internal thread conformance on 1-8 UNC fastener applications. It includes both Go and No Go members, allowing a technician to confirm that a threaded hole falls within the Class 2A tolerance range in a single setup. The gage seats into a 4-inch taperlock handle and is manufactured from tool steel for dimensional stability and wear resistance. Machinists, quality control inspectors, and toolroom technicians use this type of gage in production environments where thread verification is required before assembly.

This gage is suited for inspecting 1-8 UNC threaded holes in general industrial, mechanical, and structural applications. The 1-8 UNC designation indicates a 1-inch nominal diameter with 8 threads per inch in the Unified National Coarse series, commonly found in heavy fastener applications. The truncated taperlock design reduces contact area compared to full-form gages, lowering insertion force and extending service life in high-volume inspection routines. The included 4-inch handle provides controlled feel during gage insertion and withdrawal.

Key Features

• Go and No Go members included for complete Class 2A thread tolerance verification
• Truncated taperlock design reduces insertion force and increases gage longevity
• Tool steel construction provides hardness and dimensional stability
• Compatible with standard 4-inch taperlock handles — handle included
• Inspects 1-8 UNC internal threads in a single setup

Compatibility

Designed for use with standard taperlock-style gage handles. This gage inspects 1-8 UNC threaded holes to Class 2A tolerance specifications as defined by ASME B1.2 thread gage standards.

Installation Notes

Thread plug gages are installed and operated by quality control inspectors or machinists — no power tools or cutting is involved. Clean the threaded hole and gage members with a lint-free cloth before inspection to prevent debris from affecting readings. The Go member should pass through the full length of the thread with hand pressure only; never force a thread gage. Store gage members in a protective case away from moisture and temperature extremes to preserve calibration.