Granite surface plates are divided into four official accuracy grades based on flatness tolerance: Grade 00, Grade 0, Grade 1, and Grade 2. The grading standard is formulated according to geometric tolerance limits of flatness, with stricter flatness requirements corresponding to smaller grade numbers. Each grade matches distinct usage environments and inspection purposes.
Grade 00 (Ultra-precision grade)
This is the highest accuracy grade for granite measuring plates, with the smallest flatness error per unit length. It must be placed in constant-temperature, dust-free and vibration-isolated metrology laboratories. Main applications include calibration of standard gauges, verification of high-precision measuring instruments, and ultra-micro dimensional detection of aerospace and microelectronic parts. Ordinary production workshops cannot maintain its long-term precision due to temperature fluctuation, collision and oil pollution.
Grade 0 (High-precision grade)
Flatness tolerance is looser than Grade 00 but far superior to Grade 1. It suits precision quality inspection rooms with mild temperature changes, mold inspection workshops, new energy auto parts testing and semi-finished high-precision size verification. It can cooperate with height gauges, dial indicators and precision fixtures for daily batch precision measurement, balancing accuracy and environmental adaptability.
Grade 1 (General industrial grade)
It is the most widely used grade in machining workshops. Its shock resistance and anti-interference ability are outstanding, tolerating workshop oil mist, metal debris and frequent workpiece handling. Common uses cover routine dimensional comparison, scribing, assembly positioning and medium-precision component inspection for machinery, steel structure and welding production lines. It satisfies most factory quality control demands with favorable cost performance.
Grade 2 (Rough working grade)
This grade has the maximum flatness deviation, only applicable to rough layout, simple scribing and temporary auxiliary positioning tasks without strict measurement data recording. It cannot be adopted for formal finished product inspection requiring quality traceability, as its flatness error fails to meet metrological verification standards for dimensional testing.
The flatness tolerance value of each grade increases proportionally with the surface area of the granite plate. Larger-size measuring platforms have larger allowable flatness errors under the same accuracy grade. During selection, users should confirm the workshop environment, measurement precision demand and workpiece size to pick the matching accuracy grade.
Reference List
GB/T 7714 Format
Zhou M. Division standard and flatness tolerance calculation of granite surface plate accuracy grades[J]. Measurement Technology, 2021(12): 63-67.
MLA Format
Zhou, Ming. "Division Standard and Flatness Tolerance Calculation of Granite Surface Plate Accuracy Grades." Measurement Technology, vol. 12, 2021, pp. 63-67.
APA 7th Format
Zhou, M. (2021). Division standard and flatness tolerance calculation of granite surface plate accuracy grades. Measurement Technology, 12, 63–67.
