Addendum Dedendum Calculator

Inputs

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Choose which gear tooth-size value you know.
Module in mm, diametral pitch in 1/in, or circular pitch in mm.
mm
Tooth count used for pitch, outside and root diameters.
Standard full-depth external spur gears use c_a = 1.0.
Standard full-depth external spur gears commonly use c_b = 1.25.

Results

Default result
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Addendum(a)
2mm
Pass

Standard full-depth addendum a = m.

Radial height above the pitch circle.

Also computed

Dedendum(b)2.5mm

Standard full-depth dedendum b = 1.25m.

Radial depth below the pitch circle.

Whole depth(h_t)4.5mm

a + b.

Working depth(h_w)4mm

2a for matching standard addenda.

Root clearance(c)Pass0.5mm

Dedendum leaves root clearance for a standard mating addendum.

b - a for a mating standard addendum.

Pitch diameter(d)40mm

Outside diameter(d_a)44mm

Method notes 4 notes
  • Standard full-depth external spur gears commonly use addendum a = m, dedendum b = 1.25m, whole depth h_t = 2.25m and clearance c = 0.25m.
  • Diametral pitch converts through m = 25.4/DP. Circular pitch converts through m = p/pi.
  • Outside diameter d_a = d + 2a and root diameter d_f = d - 2b, where d = m*z.
  • This is a tooth-proportion screen. Profile shift, internal gears, stub teeth, cutter protuberance, backlash, root fillets and strength rating are separate checks.

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