| Standard | Class | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| JIS（Japan） | N0 | N1 | N2 | N3 | N4 | N5 | N6 | N7 | N8 | N9 | N10 | N11 | N12 |
| JIS-B1702-02（new） | |||||||||||||
| JGMA（Japan） | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |||||
| JIS（Japan） | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||
| JIS-B1702（old） | |||||||||||||
| PRC（China） | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| GB10095~1009 | |||||||||||||
| ISO ( International） | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| DIN（Germany） | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
| 3960~3967 | |||||||||||||
| GOST（USSR） | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |||
| BS（UK） | A1 | A2 | B | C | D | ||||||||
| FN（France） | A | B | C | D | E | ||||||||
| ANSI（USA） | 4 | 3 | 2 | 1 | |||||||||
| AGMA（USA） | 16 | 15 | 14~13 | 12 | 10 | 10 | 8 | ||||||
Gear accuracy grade refers to a standardized classification system used to define the precision and quality of gear geometry — how accurately a gear is manufactured. These grades are essential in specifying the acceptable deviation (or tolerance) in the gear’s critical dimensions and characteristics, which directly affect performance, noise, backlash, and lifespan.
Key Elements Measured in Gear Accuracy
Pitch deviation (total cumulative pitch error)
Tooth profile deviation (how accurately the tooth shape matches the ideal curve)
Helix or lead deviation (for helical gears)
Runout (eccentricity between gear center and pitch circle)
Tooth thickness variation
Concentricity and axial alignment
Common Gear Accuracy Standards
1. ISO 1328 (International)
Grades range from 1 (highest accuracy) to 12 (lowest).
Most common in global applications.
ISO grade is expressed as “ISO Grade X”, e.g., ISO Grade 6.
2. AGMA (American Gear Manufacturers Association)
Grades range from AGMA 3 to AGMA 15, where higher numbers mean higher accuracy.
Often used in North America, as well as in military and industrial applications.
Equivalent to ISO grades but with different measurement methods and tolerances.
3. DIN 3962 / DIN 3961 (German/European)
Ranges from DIN 1 to DIN 12.
DIN 4~5 is typically considered a good industrial standard; DIN 1 is for very high-precision gears (aerospace, instrumentation).
Frequently used in European machine design and gear inspection.
Practical Application Examples
| Application | Typical Grade |
|---|---|
| Watch mechanisms | ISO Grade 1–3 |
| Aerospace gearboxes | ISO Grade 3–5 |
| High-performance machine tools | ISO Grade 5–6 |
| Automotive transmissions | ISO Grade 6–8 |
| Agricultural machinery | ISO Grade 8–10 |
| General industrial machinery | ISO Grade 9–11 |
Why Gear Accuracy Grade Matters
High-grade gears (e.g., ISO 4–6): exhibit less vibration, higher torque precision, quieter operation, and improved wear characteristics.
Low-grade gears (e.g., ISO 9–12): Cheaper to produce, suitable for less demanding applications with more tolerance for noise and inaccuracy.
Lower number = higher accuracy
Choose based on application criticality, cost, and performance needs
Always match gear grades in meshing pairs to avoid premature wear or performance loss