Spi 19-644-4 Class Zz Minus Plug Pin Gage 0.644 in

Product Description

The SPI 19-644-4 is a Class ZZ minus plug pin gage with a nominal diameter of 0.644 inches and a minus tolerance of 0.0002 inches. It is used to verify hole diameters by the go/no-go method, confirming that a drilled, reamed, or bored feature meets the lower boundary of its tolerance zone. The gage is machined from steel for durability and dimensional stability under shop conditions. Machinists, toolmakers, and quality-control technicians rely on this type of gage for fast, repeatable inspection on the production floor or in the inspection room.

Class ZZ is the most commonly stocked commercial-grade pin gage class, suitable for general-purpose inspection work where ultra-precision gage tolerances are not required. This minus-style gage is held to the low side of the nominal diameter, making it appropriate for checking minimum hole size acceptance in standard tolerance applications. It fits into hand-held gage handle sets for single-pin use or can be stored in gage block and pin gage sets for organized inspection workflows.

Key Features

• 0.644-inch nominal diameter for direct hole-size verification
• Minus tolerance of 0.0002 inches (Class ZZ specification)
• Steel construction for hardness and wear resistance
• Compact, lightweight form at 0.2 pounds for easy hand use
• Compatible with standard pin gage handle sets for single-pin inspection

Compatibility

Designed as a standard Class ZZ minus plug pin gage for use with commercially available pin gage handles and sets sized for the 0.644-inch diameter range.

Installation Notes

Pin gages should be handled with clean, dry hands or lint-free gloves to prevent corrosion from skin oils. Before use, clean the gage and the hole being checked with a lint-free cloth to remove chips, coolant, or debris that could affect the reading. Do not force the gage into a hole; if resistance is felt, the feature is at or below the minimum acceptable size. Store pin gages in a protective case away from moisture and temperature extremes to maintain calibration integrity.