The Trio of Gear Precision: How Tooth Profile, Lead, And Cumulative Accuracy Dominate Noise And Service Life
Publish Time: 2026-01-22 Origin: Site
1. Three Core Elements of Gear Precision
1.1 Tooth Profile Accuracy
Total tooth profile deviation (Fα): The distance between two design tooth profile traces that enclose the actual tooth profile trace within the evaluation range.
Tooth profile form deviation (ffα): The total tooth profile deviation after excluding the inclination component, reflecting shape errors such as convexity or concavity.
Tooth profile inclination deviation (fHα): The deviation of the line connecting the two endpoints of the actual tooth profile trace from the line connecting the two endpoints of the design tooth profile trace within the evaluation range.
| Accuracy Grade | Application Scope | Maximum Circumferential Speed (m/s) |
|---|---|---|
| Grade 4 | Gears for ultra-precision indexing mechanisms, high-speed gears requiring smooth and noise-free operation, high-speed turbine gears, and ideal precision gears for inspecting Grade 7 gears. | Spur gear: <70; Helical gear: <40 |
| Grade 5 | Gears for precision indexing mechanisms, high-speed gears requiring smooth and noise-free operation, high-speed turbine gears, and ideal measuring gears for inspecting Grade 8 and 9 gears. | Spur gear: <35; Helical gear: <20 |
| Grade 6 | High-speed, smooth, noise-free, and high-efficiency gears; important gears in aerospace, machine tools, and automobiles; gears for indexing mechanisms and reading mechanisms. | Spur gear: <30; Helical gear: <15 |
| Grade 7 | Small high-speed power gears requiring reversal, feed gears in machine tools, aerospace gears, reading mechanism gears, and reducer gears with a certain speed. | Spur gear: <15; Helical gear: <10 |
| Grade 8 | Ordinary gears in general machinery; general gears in automobiles, tractors, and reducers; non-critical gears in aircraft; and important gears in agricultural machinery. | Spur gear: <10; Helical gear: <6 |
| Grade 9 | Gears with low precision requirements | - |
1.2 Lead Accuracy
Total lead deviation (Fβ): The distance between two design tooth line traces that enclose the actual tooth line trace within the evaluation range.
Helix form deviation (ffβ): The total lead deviation after excluding the inclination component.
Helix inclination deviation (fHβ): The deviation of the line connecting the two endpoints of the actual tooth line trace from the line connecting the two endpoints of the design tooth line trace within the evaluation range.
| Individual Tolerance | Standard | Accuracy Grade Correspondence |
|---|---|---|
| F | ISO; GB/T | 3, 4, 5, 6, 7, 8, 9, 10 |
| DIN | 4, 5, 6, 7, 8, 9, 10, 11 |