Spi 29-308-4 Class Zz Plus Plug Gage 0.308 in

Product Description

The SPI 29-308-4 is a Class ZZ Plus plug gage designed to verify bore and hole diameters to a nominal size of 0.308 inches with a tolerance of 0.0002 inches. Built from steel, this go/no-go style precision gage gives machinists, quality control inspectors, and tool-room technicians a fast, reliable method for checking inside diameter conformance on production parts. Class ZZ is the standard tolerance grade for general inspection work, and the Plus designation indicates the gage is made to the upper end of that tolerance range, extending usable service life as the gage wears over time.

This plug gage is suited for use in manufacturing, machine shops, and inspection departments where consistent bore verification is required. It is appropriate for both incoming inspection and in-process quality checks on steel, aluminum, and other machined components where a 0.308-inch nominal bore must be confirmed to tight dimensional standards. The compact, single-piece form makes it easy to handle and store.

Key Features

• Nominal measurement diameter of 0.308 inches for precise bore checking
• Tolerance of 0.0002 inches meets Class ZZ Plus accuracy requirements
• Steel construction for durability and dimensional stability in shop environments
• Plus tolerance designation extends gage service life as wear occurs
• Compact single-piece form — no additional tooling required for use

Compatibility

Designed as an OEM-style inspection gage for verifying 0.308-inch nominal inside diameters in standard machining and quality control applications.

Installation Notes

Plug gages are used by quality control inspectors and machinist trades — no installation in the traditional sense applies. Before use, clean the gage and bore thoroughly to remove chips, oil, and debris that could affect the reading. Store the gage in a protective case away from other tools to prevent surface damage. Periodic calibration against NIST-traceable standards is recommended to confirm ongoing dimensional accuracy.