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
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Auxiliary Geometric Calculations |
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Design of module, Number of teeth, Worm diameter factor and correction |
Calculated parameters
Common gearing ZN
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Axial module |
m n = m |
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Normal module |
m x = m n cos γ |
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Axial pressure angle |
α x = a |
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Normal pressure angle |
α n = arctg (tg α cos γ) |
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Helix/lead angle |
γ = arcsin z 1 /q |
Spiral gearing ZA
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Axial module |
m n = m x / cos γ |
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Normal module |
m x = m |
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Axial pressure angle |
α n = arctg (tg α cos γ) |
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Normal pressure angle |
α x = α |
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Helix/lead angle |
γ = arctan z 1 /q |
Normal tooth pitch
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p n = π m n |
Axial tooth pitch
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p x = π x |
Basic tooth pitch
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p b = p x cos α x |
Lead
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p z = z 1 p x |
Virtual/alternate number of teeth
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Helix angle at basic cylinder
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sin γ b = sin γ cos α n |
Worm pitch cylinder diameter
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d 1 = q m |
Worm gear pitch circle diameter
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d 2 = z 2 m x |
Worm outside cylinder diameter
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d a1 = d 1 + 2mh a * |
Worm gear outside circle diameter
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d a2 = d 2 + 2m (h a * + x) |
Worm root cylinder diameter
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d f1 = d 1 - 2m (h a * + c * ) |
Worm gear root circle diameter
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d f2 = d 2 - 2m (h a * + c * - x) |
Worm rolling(work) circle diameter
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d w1 = d 1 + 2xm |
Worm gear rolling(work) circle diameter
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d w2 = d 2 |
Worm gear root circle diameter
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d b2 = d 2 cos α x |
Center distance
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Chamfer angle of worm gear rim
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Worm tooth thickness in normal plane
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Worm gear tooth thickness in normal plane
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Worm tooth thickness in axis plane
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s x1 = s 1 / cos γ |
Worm gear tooth thickness in axis plane
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s x2 = s2 / cos γ |
Work face width
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b w = min (b 1 , b 2 ) |
Contact ratio
ε = ε + ε
where:
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Minimum worm gear tooth correction
where:
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h a * 0 = h a * + c * - r f * (1 - sin α) |
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c = 0.3 |
for α = 20 degrees |
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c = 0.2 |
for α = 15 degrees |
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