Spi 29-638-4 Class Zz Plus Plug Gage 0.638 in

Product Description

The SPI 29-638-4 is a Class ZZ Plus plug gage designed for go/no-go dimensional inspection of bored holes, drilled passages, and machined apertures measuring 0.638 inches in diameter. Built to Class ZZ Plus tolerance standards, it holds a tolerance of 0.0002 inches, making it suitable for production-floor inspection work where consistent, repeatable measurement is required. The gage body is constructed from steel for durability and wear resistance. Machinists, quality control technicians, and tool-and-die professionals reach for plug gages like this to verify that finished features fall within drawing specification before parts advance to the next stage of production.

This plug gage is suited for use in machine shops, manufacturing facilities, and job shops performing dimensional verification on parts produced by drilling, boring, reaming, or honing. It is appropriate for both incoming inspection and in-process quality checks on any application requiring confirmation that a 0.638-inch diameter feature meets tolerance. The compact size and single-diameter design make it a straightforward, dedicated inspection tool for high-volume or repetitive checking tasks.

Key Features

• Class ZZ Plus accuracy with a 0.0002-inch tolerance for reliable dimensional verification
• Nominal diameter of 0.638 inches for dedicated single-size inspection
• Steel construction provides hardness and long service life under repeated use
• Lightweight at 0.2 pounds for easy single-hand operation during inspection cycles
• Single-piece plug format — no adjustments required, consistent from use to use

Compatibility

Designed as an OEM-style plug gage for dimensional inspection of 0.638-inch diameter features in machined metal, plastic, or composite workpieces across standard production and quality assurance applications.

Installation Notes

Plug gages are handled and stored by quality control technicians and machinists — no power source, wiring, or fluid shutoff is required prior to use. Keep the gage clean and lightly oiled when not in use to prevent corrosion of the steel contact surfaces. Do not force the gage into an undersized feature, as this can damage the gage land or alter its calibration. Periodic re-calibration against a certified master reference is recommended to maintain measurement traceability.