Spi 29-418-1 Class Zz Plus Plug Gage 0.418 Inch

Product Description

The SPI 29-418-1 is a Class ZZ Plus plug gage used to verify the inside diameter of bored, drilled, or reamed holes to a nominal size of 0.418 inches. Manufactured from steel, it holds a tolerance of 0.0002 inches, making it suitable for precision inspection work in machine shops, manufacturing facilities, and quality control environments. Metrologists, machinists, and quality inspectors use plug gages like this to confirm that a hole falls within acceptable dimensional limits before parts move to assembly. The go/no-go principle applied with Class ZZ gages provides fast, repeatable pass-fail verification without the need for electronic measuring equipment.

This gage is appropriate for general-purpose dimensional inspection of production and replacement parts where a 0.418-inch nominal hole diameter must be confirmed. Class ZZ Plus tolerancing places it in the range used for inspection of commercial-grade work rather than ultra-precision aerospace or gauge-block-level applications. It is a single gage member and is typically paired with a handle or used as part of a go/no-go set. Suitable for use on steel, aluminum, plastic, and other common workpiece materials.

Key Features

• 0.418-inch nominal measurement diameter for precise hole verification
• Class ZZ Plus tolerance grade at 0.0002 inches for reliable pass-fail inspection
• Steel construction for durability and dimensional stability during repeated use
• Compact and lightweight at 0.2 pounds for easy bench or field use
• Single-piece design compatible with standard plug gage handles

Compatibility

Designed as an OEM-style replacement or standard inspection gage member for use wherever a 0.418-inch diameter Class ZZ Plus plug gage is specified. Compatible with standard plug gage handles sized for this diameter range.

Installation Notes

Plug gages should be handled with clean, dry hands or inspection gloves to prevent corrosion from skin oils that can affect dimensional accuracy. Before use, verify the gage and workpiece are at the same ambient temperature, typically 68 degrees F, to eliminate thermal expansion error. Store the gage in its protective case when not in use and periodically verify calibration against a traceable reference standard per your quality system requirements. No special tools are required for use, but a proper gage handle is recommended for safe and repeatable insertion.