I. Executive Standards
Manufacturing Standard: JB/T 10027-2017 “Granite Surface Plates, Straight Edges, Squares, and Square Boxes”
Verification Standard: JJG 117-2013 “Verification Regulation for Surface Plates”
Accuracy Grade: Grade 000, Grade 00, Grade 0 (the smaller the number, the higher the accuracy); some scenarios still use the old standard Grade 1 (General Industrial Grade).
II. Grade Definitions and Applications
Grade 000 (Reference Grade): Metrology rooms / Constant temperature laboratories, used for value transfer and standard calibration.
Grade 00 (Precision Grade): Precision quality inspection, CMM debugging, mold / aerospace part inspection.
Grade 0 (Industrial Grade): Workshop on-site inspection, marking, machine tool alignment.
Grade 1 (General Grade, Old Standard): General machining, fitter marking.
III. Core Tolerances (Unit: μm, Typical values for 200×200×200mm)
Tableau
Accuracy Grade | Working Surface Flatness | Relative Surface Parallelism | Adjacent Surface Perpendicularity
Grade 000 | 1.5 | 2 | 2
Grade 00 | 1.5 | 2 | 2
Grade 0 | 3 | 4 | 4
IV. Tolerance Patterns
The larger the size, the larger the tolerance (e.g., 400×400×400mm: Grade 00 perpendicularity ≈ 3μm, Grade 0 ≈ 6μm).
Temperature Reference: Verification / usage temperature 20±2℃ to avoid thermal expansion and contraction affecting accuracy.
V. Difference from Squares
Square: Single-sided / double-sided right-angle reference, focusing on flatness right angle.
Square Box: Six-sided three-dimensional reference, fully controlling flatness, parallelism, and perpendicularity, can be flipped and used on multiple sides.
VI. Selection Recommendations
Metrology Calibration → Grade 000
Precision Inspection → Grade 00
Workshop On-site → Grade 0
General Marking → Grade 1
Granite Square Block Tolerance Quick Reference Table (Based on JB/T 10027-2017) Unit: μm, Standard Calibration Temperature: (20\pm2^\circ\text{C})
Dimensions: Length × Width × Height (Cubic square block, mainstream industrial specifications)
Controlled Items: Flatness of working surface, Parallelism of opposite faces, Perpendicularity of adjacent faces
I. Complete Tolerance Table
Table Specifications (mm) Accuracy Grade Flatness Parallelism Perpendicularity
100×100×100 000 Grade 0.8 1.0 1.0
100×100×100 00 Grade 1.2 1.5 1.5
100×100×100 0 Grade 2.0 2.5 2.5
150×150×150 000 Grade 1.0 1.2 1.2
150×150×150 00 Grade 1.5 2.0 2.0
150×150×150 0 Grade 2.5 3.0 3.0
200×200×200 000 Grade 1.5 2.0 2.0
200×200×200 00 Grade 1.5 2.0 2.0
200×200×200 0 Grade 3.0 4.0 4.0
250×250×250 000 Grade 1.8 2.2 2.2
250×250×250 00 Grade 2.0 2.5 2.5
250×250×250 0 Grade 3.5 4.5 4.5
300×300×300 000 Grade 2.0 2.5 2.5
300×300×300 00 Grade 2.5 3.0 3.0
300×300×300 0 Grade 4.0 5.0 5.0
400×400×400 000 Grade 2.5 3.0 3.0
400×400×400 00 Grade 3.0 3.5 3.5
400×400×400 0 Grade 5.0 6.0 6.0
500×500×500 000 Grade 3.0 3.5 3.5
500×500×500 00 Grade 3.5 4.0 4.0
500×500×500 0 Grade 6.0 7.0 7.0
630×630×630 000 Grade 3.8 4.2 4.2
630×630×630 00 Grade 4.2 4.8 4.8
630×630×630 0 Grade 7.0 8.0 8.0
II. Supplementary Notes
Tolerance Pattern
The larger the external dimensions of the square block, the larger the allowable error; for the same specification: (\boldsymbol{000 Grade < 00 Grade < 0 Grade}), accuracy decreases grade by grade.
Old Standard Supplement (Grade 1, small amount in circulation on the market)
Used only for ordinary workshop marking and rough inspection, tolerances are much larger than Grade 0, e.g., 200mm specification Grade 1 perpendicularity ≤ 8 μm.
Supporting Calibration Basis
Finished product factory inspection / periodic re-inspection follows: JJG 117-2013 Calibration Regulation for Surface Plates.
Quick Selection Reference
000 Grade: Metrology rooms, value transfer, standard instrument calibration
00 Grade: Precision machining quality inspection, CMM / vision system debugging, aerospace / mold high-precision inspection
0 Grade: Machining workshops, routine inspection, fitter’s 3D marking, workpiece alignment
