Spi 19-639-4 Class Zz Minus Plug Pin Gage 0.639 in

Product Description

The SPI 19-639-4 is a Class ZZ minus plug pin gage machined to a 0.639-inch nominal diameter with a tolerance of 0.0002 inches. Plug pin gages are precision hand tools used to verify that a drilled, reamed, or machined hole falls within an acceptable size range. The minus designation means the gage is ground to the lower tolerance boundary, making it a go-gage for checking minimum hole size. Machinists, toolmakers, and quality control inspectors use plug gages as a fast, reliable alternative to inside micrometers when checking high-volume or production hole dimensions. The 19-639-4 is constructed from steel for durability and dimensional stability.

This gage is suited for use in machine shops, manufacturing facilities, and inspection departments working with precision-drilled or reamed through-holes and blind holes. It is commonly used during in-process inspection and final quality verification of machined components across metalworking, fabrication, and light manufacturing environments. The compact, single-ended form factor makes it practical for bench use and on-machine checks.

Key Features

• Class ZZ tolerance class, appropriate for general-purpose production and inspection work
• Minus designation ground to lower tolerance limit for go-gage application
• 0.639-inch nominal diameter with 0.0002-inch tolerance
• Steel construction for wear resistance and dimensional stability
• Single-piece form factor for quick, repeatable hand inspection

Compatibility

Designed as a direct-use plug pin gage for any application requiring inspection of a 0.639-inch nominal diameter hole to Class ZZ minus standards.

Installation Notes

Plug pin gages do not require installation, but proper handling is essential to maintain accuracy. Always clean the gage and the hole being checked before use to remove chips, oil, or debris that can affect measurement. Store the gage in a protective case or sleeve when not in use to prevent surface damage. Inspection work involving precision gages should follow applicable quality system procedures and regular calibration intervals.