KEVOS® MAKEOS · Gears
Spur Gear Dimensions (Diametral Pitch)
What are the diameters, tooth depth and centre distance of this inch (diametral pitch) spur gear pair?
Pitch, outside and root diameters, addendum, dedendum, whole depth, circular pitch, tooth thickness and centre distance of a diametral-pitch spur gear pair, with metric equivalents.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Diametral pitch | 1/in | Diametral pitch (teeth per inch of pitch diameter). |
| Pinion teeth | teeth | Pinion tooth count. |
| Gear teeth | teeth | Gear tooth count. |
| Tooth system | choice | Tooth proportions of the gear system. |
Method and formulas
- Pitch diameter = N ÷ P; addendum a = 1/P (stub 0.8/P).
- Dedendum b = 1.25/P (20° FD), 1.157/P (14½° FD), 1/P (stub); OD = (N + 2aP) ÷ P; root = PD − 2b.
- Circular pitch = π ÷ P; tooth thickness = π ÷ 2P; centre distance = (N₁ + N₂) ÷ 2P; module = 25.4 ÷ P.
- Example: 10 DP, 20 teeth: PD 2 in, OD 2.2 in, centre distance 3.25 in.
Limitations
- Standard proportions; fine-pitch gears (20 DP and finer) add a clearance allowance to the dedendum.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Machine or replace inch-system gears
- Convert diametral pitch to module
- Check gear blank diameters
Who it is for
- Gear designers
- Machinists
- Maintenance engineers
What you get
- Pitch, outside and root diameters
- Addendum, dedendum and whole depth
- Circular pitch and tooth thickness
- Centre distance and equivalent module
Interpreting the result
- Turn gear blanks to the outside diameter before cutting.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2131–2140, 2249–2251. Topic reference; no source tables or recommended settings are reproduced.
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