Spi 29-389-4 Class Zz Plus Plug Gage 0.389 in Steel

Product Description

The SPI 29-389-4 is a Class ZZ Plus plug gage designed to verify the inside diameter of machined holes, bores, and other cylindrical features to a nominal size of 0.389 inches. Manufactured from steel, this go/no-go style gage provides a tolerance of 0.0002 inches, making it suitable for production inspection and quality control applications where dimensional accuracy is critical. Machinists, tool-and-die technicians, and quality control inspectors use plug gages like this to confirm that drilled, reamed, or bored holes fall within specified tolerance bands before parts move to the next stage of production.

This plug gage is appropriate for use in machine shops, manufacturing facilities, and precision fabrication environments. It is commonly employed during in-process inspection and final inspection of components where hole diameter conformance must be documented. The 0.389-inch nominal diameter and Class ZZ Plus classification make it a standard choice for general-purpose dimensional verification in both light production and job-shop settings.

Key Features

• Nominal measurement diameter of 0.389 inches for precise hole verification
• Class ZZ Plus tolerance of 0.0002 inches for reliable go/no-go inspection
• Steel construction for durability in shop-floor environments
• Compact and lightweight at 0.2 pounds for easy single-hand use
• Single-piece package quantity suitable for individual station or kit use

Compatibility

Designed as a general-purpose OEM-style plug gage for verifying 0.389-inch nominal inside diameters on machined components across a wide range of materials and part types.

Installation Notes

Plug gages are handled by machinists and quality control technicians and require no installation in the traditional sense. Before use, clean both the gage and the workpiece bore thoroughly to remove chips, coolant, and debris that could affect the reading. Do not force the gage into an undersized hole, as this can damage the gage surface and alter its calibration. Store the gage in a protective case when not in use to prevent nicks and wear that would compromise measurement integrity.