Spi 29-312-6 Class Zz Plus Plug Gage 0.312 in

Product Description

The SPI 29-312-6 is a Class ZZ Plus plug gage used to verify the internal diameter of machined holes to a nominal size of 0.312 inches. It holds a tolerance of 0.0002 inches, meeting Class ZZ Plus standards for general-purpose go/no-go inspection work. The gage is constructed from steel for durability and dimensional stability under shop-floor conditions. Machinists, quality control technicians, and tool-and-die professionals use plug gages like this to confirm bore acceptance during production and incoming inspection without requiring a CMM or air gage setup.

This plug gage is suited for use in production machining environments, job shops, and inspection departments where quick, repeatable hole verification is required. It is appropriate for both ferrous and non-ferrous workpieces where 0.312-inch nominal bores must be validated to tight dimensional tolerances. The compact size and low weight make it easy to handle during high-volume inspection runs.

Key Features

• Class ZZ Plus tolerance class for general-purpose hole inspection
• Nominal diameter of 0.312 inches for precise bore verification
• Tolerance of 0.0002 inches for reliable go/no-go measurement
• Steel construction for wear resistance and dimensional stability
• Lightweight at 0.2 pounds for easy single-hand operation

Compatibility

Designed as a general-purpose Class ZZ Plus plug gage for verifying 0.312-inch nominal internal diameters in machined components across standard production and inspection applications.

Installation Notes

Plug gages are handled by qualified machinists or inspection personnel and require no installation in the traditional sense. Clean both the gage and the bore thoroughly before use to prevent false readings caused by chips or coolant residue. Store the gage in its protective case when not in use to preserve the ground surfaces and prevent corrosion. Handle with clean hands or cotton gloves to avoid introducing thermal expansion error from body heat during measurement.