General Selection Rules
- Prioritize National Standards: Select values strictly according to the GB/T 1357-2008 standard module series. Prioritize the "First Series," followed by the "Second Series," and avoid using modules listed in parentheses whenever possible.
- Strength-First Principle: Calculate the theoretical module based on tooth surface contact strength and tooth root bending strength. While meeting strength requirements, select the smallest possible standard module to minimize gear volume and reduce manufacturing costs.
- Operating Condition Adaptation: Choose a smaller standard module for high-speed applications and a larger one for low-speed, heavy-load applications. For open gear drives, increase the module size to compensate for strength loss caused by wear.
Specific Selection Methods for Different Gear Types
Spur Gears (Straight-toothed Cylindrical Gears)
Use the transverse module(end-face module) as the standard module and select the corresponding value directly from the national standard series.
For power transmission, the module should be ≥1.5 mm to ensure sufficient tooth strength. Ideally, select a tooth count between 20 and 40; when the center distance is fixed, the standard module can be finalized by adjusting the tooth count.
Helical Gears (Helical-toothed Cylindrical Gears)
Use the normal module as the standard module; this aligns with the feed reference for machining tools and complies with GB/T 10095 manufacturing specifications.
During geometric dimensioning, convert values to transverse parameters, adjust the center distance based on the helix angle, and finally map the result back to a standard normal module.
Straight Bevel Gears
Use the large-end module as the standard module. Dimensions at the large end are easier to measure and involve smaller machining errors, making it the reference parameter for bevel gear design.
