Granite Straight Edge

The primary metrological function of granite straightedges is to serve as a high-accuracy reference standard for the assessment of straightness and flatness in precision engineering applications.
1. Linear guide rail verification: Granite straightedges are employed to evaluate the straightness deviation of linear guideways on machine tools, coordinate measuring machines (CMMs), and other precision motion systems—typically in accordance with ISO 230-1:2012.
2. Large workpiece surface inspection: During mechanical manufacturing processes, they are utilized to assess the flatness of large-scale machined surfaces. Quantitative evaluation is commonly performed using calibrated feeler gauges, while qualitative assessment may employ the light-gap method—where uniformity and magnitude of transmitted light between the straightedge and surface provide an indication of local deviations from ideal flatness.