Spi 19-421-7 Class Zz Minus Plug Pin Gage 0.421 in

Product Description

The SPI 19-421-7 is a Class ZZ minus plug pin gage with a nominal diameter of 0.421 inches, manufactured from steel. It is used to verify hole diameters and bore dimensions by providing a go/no-go reference at a tight tolerance of 0.0002 inches. Class ZZ is the standard tolerance grade for general-purpose inspection work, making this gage suitable for incoming inspection, quality control on the shop floor, and production verification tasks. Machinists, tool-and-die makers, and quality technicians are the typical end users.

This gage is suited for dimensional inspection of drilled, reamed, or bored holes in metal, plastic, and composite workpieces. It functions as a minus plug gage, meaning the gage diameter is at the low end of the tolerance band, consistent with Class ZZ specification. It is used in both job-shop and production environments where repeatable hole verification is required without the need for higher-precision Class ZY or Class X gages.

Key Features

• Nominal diameter of 0.421 inches for direct hole verification at that dimension
• Class ZZ tolerance grade for general-purpose dimensional inspection
• Minus designation places gage at the low side of the tolerance band
• Tolerance of 0.0002 inches for consistent, repeatable measurement results
• Steel construction for durability and resistance to wear during repeated use

Compatibility

Designed as a general-purpose plug pin gage for use with any standard gage handle or holder that accepts a 0.421-inch pin gage, in accordance with Class ZZ dimensional inspection applications.

Installation Notes

Plug pin gages are handled and used by machinists and quality control inspectors — no power tools or electrical lockout is required. Keep the gage clean and lightly oiled when not in use to prevent corrosion and maintain dimensional integrity. Do not force the gage through an undersized hole, as this can damage the gage surface and introduce measurement error. Store in a protective case away from temperature extremes to preserve the steel substrate and hold tolerance.