The hardness and stability allow accuracies within millionths of an inch. Along with the high accuracies, granite is rust-proof, non-magnetic, abrasive resistant, non wedging, wrap-resistant and easily cleaned. The granite used for surface plates has an excellent distribution of hard quartz which provides a smooth, long-wearing working surface.
Granite surface plates meet or exceed Federal Specifications GGG-P463. Final inspection and calibration of every surface plate is accomplished by use of the Auto-Collimeter
Grade "B" Toolroom ± 100 Millionths
Grade "A" Inspection ± 50 Millionths
* NOTE: Specify when ordering "Granite Stands", "O" Ledge or 2-Ledge. *