What are the standard modules for helical gears in mechanical design? How to choose?

Involute cylindrical gear module according to GB/T 1357, there is no separate module series for helical gears, helical gear normal modulus according to the modulus of spur gears for parameter calculation.

Module first series:

0.1 0.12 0.15 0.2 0.25 0.3 0.4 0.5 0.6 0.8 1 1.25 1.5 2 2.5 3 4 5 6 8 10 12 16 20 25 32 40

The second series are:

0.35 0.7 0.9 1.75 2.25 2.75 ( 3.25) 3.5 (3.75) 4.5 5.5 (6.5)

7 9 (11) 14 18 22 28 36 45

Preference is given to the first series, with values in parentheses not used where possible.

Unit: mm.

The selection of modulus of gears should be calculated according to the load condition, and take into full consideration of a series of elements such as bending strength of tooth root, contact strength of tooth surface, material, heat treatment condition, etc. Here, we can't simply answer the question of how to select, which is a science. Need to specialize in learning, accumulate experience, in order to do a good job.