Spi 29-439-7 Class Zz Plus Plug Gage 0.439 in

Product Description

The SPI 29-439-7 is a Class ZZ Plus plug gage designed for precision go/no-go inspection of drilled, reamed, or bored holes. It measures hole diameters at exactly 0.4390 inches with a tolerance of 0.0002 inches, making it suited for medium-tolerance production inspection and quality control workflows. Constructed from steel, this gage provides the durability needed for repeated use on the shop floor. Machinists, quality technicians, and tool-and-die professionals use Class ZZ plug gages to verify bore dimensions quickly and consistently without the need for indicating instruments.

This plug gage is used in machine shops, manufacturing facilities, and toolrooms where hole size verification is a routine part of production or incoming inspection. It is appropriate for checking holes in metal, plastic, or composite workpieces where dimensional conformance must be documented or confirmed before assembly. The 0.4390-inch nominal diameter targets a common bore size found across a wide range of machined components and fixtures.

Key Features

• Class ZZ Plus accuracy with 0.0002-inch tolerance for reliable go/no-go inspection
• Nominal diameter of 0.4390 inches targets common machined bore sizes
• Steel construction for wear resistance and dimensional stability
• Compact and lightweight at 0.2 pounds for easy bench or in-process use
• Single-piece package quantity suitable for individual station use

Compatibility

Designed as an OEM-style replacement or direct-use plug gage for any go/no-go inspection application requiring a 0.4390-inch nominal diameter at Class ZZ Plus tolerance.

Installation Notes

Plug gages are handled and used by quality technicians and machinists and require no permanent installation. Keep the gage clean and lightly oiled when not in use to prevent corrosion and maintain dimensional accuracy. Do not force the gage into an undersized hole, as this can damage the gage or the workpiece and will produce an invalid measurement. Store in a protective case away from temperature extremes to preserve calibration integrity.