Accuracy and Calibration of Granite Surface Plates
• Discusses the accuracy and calibration of granite surface plates based on ANSI ASME B89.3.7-2013.
• Surface plates are massive, stiff, and hard granite plates with a flat, smooth top work surface.
• The quality of surface plates was standardized through Federal Specification GGG-P-463c, which was inactive in 2013 with the publication of ASME B89.3.7.
• The focus is on surface plate flatness, a crucial metrological characteristic, subject to routine calibration.
• ASME B89.3.7 defines standardized tolerance grades for surface plates, with highest accuracy being Grade AA, lowest accuracy being Grade B, and middle grade plates, Grade A.
• Calibration involves checking conformance to two different tolerance values.