Basic Geometric Calculation for Worm Gears
Input Parameters
Teeth type - common or spiral
Gear ratio and tooth numbers 
Pressure angle (the angle of tool profile) α
Module m (With ANSI - English units, enter tooth pitch p = π m)
Unit addendum ha *
Unit clearance c *
Unit dedendum fillet r f *
Face widths b 1 , b 2
Unit worm gear correction x
Worm size can be specified using the:
- worm diameter factor q
- helix direction γ
- pitch diameter d 1
Auxiliary Geometric Calculations |
Design of module, Number of teeth, Worm diameter factor and correction |
Calculated parameters
Common gearing ZN
Axial module | m n = m | |
Normal module | m x = m n cos γ | |
Axial pressure angle | α x = a | |
Normal pressure angle | α n = arctg (tg α cos γ) | |
Helix/lead angle | γ = arcsin z 1 /q |
Spiral gearing ZA
Axial module | m n = m x / cos γ | |
Normal module | m x = m | |
Axial pressure angle | α n = arctg (tg α cos γ) | |
Normal pressure angle | α x = α | |
Helix/lead angle | γ = arctan z 1 /q |
Normal tooth pitch
Axial tooth pitch
Basic tooth pitch
Lead
Virtual/alternate number of teeth
Helix angle at basic cylinder
Worm pitch cylinder diameter
Worm gear pitch circle diameter
Worm outside cylinder diameter
Worm gear outside circle diameter
Worm root cylinder diameter
Worm gear root circle diameter
Worm rolling(work) circle diameter
Worm gear rolling(work) circle diameter
Worm gear root circle diameter
Center distance
Chamfer angle of worm gear rim
Worm tooth thickness in normal plane
Worm gear tooth thickness in normal plane
Worm tooth thickness in axis plane
Worm gear tooth thickness in axis plane
Work face width
Contact ratio
ε γ = ε α + ε β
where:
Minimum worm gear tooth correction
where: