Granite Surface Plate 15.7 x 9.8 x 2.36 in - Grade A Precision

In this review of the 15.7 x 9.8 x 2.36 in Grade A Granite Surface Plate the bottom line is straightforward: it is a practical, stable reference surface for small shops and inspection benches where flatness matters more than traceable calibration. The plate's top surface is precision ground to a high degree of flatness with an accuracy of +/-.0001 in, and it ships with a certificate of inspection that confirms compliance with Federal Specifications. For someone needing a non-magnetic, hard work surface for layout, height gaging, and visual inspection, this plate offers strong value.

Key Features

• Precision ground top: The top surface is ground to achieve high flatness, giving a reliable reference for measuring and laying out parts.
• Grade A accuracy: With Grade A (Grade 0) accuracy of +/-.0001 in, the plate is suited to close-tolerance inspection tasks common in small machine shops.
• Certificate of inspection: Each plate includes a certificate that shows it meets or exceeds Federal Specifications GGG-P-463C, useful for shop records.
• Non-magnetic and non-conductive: Being granite, the surface will not magnetically interfere with sensitive parts and is electrically insulating.
• Durable work surface: Harder than steel, the plate resists nicks and burrs and serves well for assembly, marking, and setup work.
• Versatile usage: Useful for checking flatness, squareness, parallelism, perpendicularity and as a stable base for height gages.

Who It's For

This plate is best for small to medium machine shops, inspection benches, toolrooms, and hobbyists who need a stable, hard reference surface for layout work and height gaging. The size is convenient for bench-top use and offers ample area for many common dimensional checks without occupying a large footprint.

Those who require NIST-traceable certification, very large surface plates, or a mirror-polished finish should look elsewhere; the included certificate confirms federal spec compliance but does not provide NIST traceability, and customer feedback indicates surface smoothness can vary between units.

Pros & Cons

Pros

• High flatness accuracy of +/-.0001 in delivers a reliable reference for precision checks.
• Durable, non-magnetic granite resists nicks and is a stable work surface for assembly and inspection.
• Includes a certificate of inspection and meets Federal Specifications GGG-P-463C for quality assurance.

Cons

• Not NIST traceable and some buyers report variability in surface smoothness or polish between units.

Specifications

Model	4401-4025
Material	Granite
Overall size	15.7 x 9.8 x 2.36 in
Grade / Accuracy	Grade A (Grade 0), +/-.0001 in
Standards	Meets or exceeds Federal Specifications GGG-P-463C
Certificate	Included (not NIST traceable)
Properties	Non-magnetic, non-conductive, harder than steel

Our Verdict

The HHIP 15.7 x 9.8 x 2.36 in Grade A Granite Surface Plate is a sensible, cost-effective choice for shops that need a dependable flat reference and a tough work surface without the premium of traceable calibration. It is good value for bench-level inspection, layout, and height gage work, though buyers seeking perfect surface polish or NIST traceability should consider higher-tier options.

Frequently Asked Questions

Does this plate come with calibration paperwork?
Yes, it ships with a certificate of inspection confirming compliance with Federal Specifications GGG-P-463C, but it is not NIST traceable.

Is the surface magnetic or conductive?
No, the granite surface is non-magnetic and non-conductive, making it suitable for work on delicate electronic or magnetic parts.

Can I use this plate for height gage measurements?
Yes, the plate is intended as a stable reference for height gages, checking flatness, squareness, and other dimensional tasks.