The flatness tolerance of a granite surface plate refers to the permissible deviation in the flatness of its working surface, which must comply with the specific accuracy grade. For surface plates, the flatness of the central area, where concentrated loads are applied, as well as the rated load and allowable deflection, must meet national standards.
When inspecting the flatness of a surface plate using diagonal or grid methods, it is essential to measure the fluctuation of the plane. Plates with a grade of 0.000 or 00 should generally not have handles, as this could affect their accuracy.
The verticality tolerance of the plate's sides relative to the working surface, as well as the verticality between adjacent sides of the plate, must adhere to the standards outlined in GB/T1184, specifically grade 12.
The surface roughness of the working surface of the granite plate should not exceed Ra 0.32-0.63 µm, while the side surfaces should be limited to Ra 10 µm. For optimal performance, the granite plate should be made from fine-grained, dense materials such as diorite, basalt, or granite, with less than 5% black mica content. The material's elastic modulus should be greater than 0.6×10⁴.
Conclusion:
Granite surface plates with precise flatness tolerance are crucial for high-accuracy measurements. Ensuring that the surface plate meets these tolerances, along with using high-quality, fine-grained materials, will guarantee long-lasting performance and maintain the accuracy of your measurements in various industrial applications.