⚙ Gear Pitch Calculator
Calculate Diametral Pitch, Module, Pitch Diameter, Outside Diameter & Full Tooth Geometry
| Diametral Pitch (DP) | Module (mm) | Circular Pitch (in) | Typical Application |
|---|
| DP | Module (mm) | Pitch Dia. (in) | Outside Dia. (in) | Addendum (in) | Whole Depth (in) |
|---|
| Pressure Angle | Tooth Strength | Noise Level | Undercutting Risk | Best Use |
|---|---|---|---|---|
| 14.5° | Moderate | Low (smooth) | Higher | Legacy clocks, instruments |
| 20° (Standard) | High | Low–Moderate | Low | General machinery, automotive |
| 25° | Very High | Higher | Very Low | Heavy-load, aerospace |
The pitch of a Gear in short is the size of the teeth on it; seems something easy, but there are many small details about how one measures and talks about that. When we talk about Gears, one uses three main ways to describe the pitch: diametral pitch, circular pitch and module (that some call metric pitch). In the United States diametral pitch is the most commonly used.
Diametral pitch shows how many teeth fit in one inch of the diameter of the Gear. If you fit more teeth in that same length, the pitch becomes smaller. It is a reverse relation, the bigger the number of diametral pitch, the less space between the teeth.
Gear Pitch: What It Is and How to Measure
The pitch simply relates the number of teeth on the Gear to its diameter.
To find the diameter of the pitch, simply divide the number of teeth by the diametral pitch. If you want to count the pitch of some Gear that you found lying around? Measure its outer diameter, count the teeth, add two to that amount, and then divide by the outside diameter.
Such a little trick helped me many tiems, when I found mystery Gears lying around.
Here is where the pitch circle comes in; it is a fixed circle that wood give the same motion through pure roll, as do the real teeth of the Gear. And the diameter of the pitch? It is simply the size of that fixed circle.
If one imagines the Gears as rolls that touch one another along that pitch circle at one single line of contact, then the teeth serve only to stop skating. Two Gears touch one another at what one calls the pitch point.
Circular pitch works a bit differently. It shows the distance that one measures along the pitch circle from one spot on a tooth to the same spot on the next tooth. If you multiply the circular pitch by the number of teeth, you get the full length around the pitch circle.
Module is another important way to describe the size of teeth, and it is based on ISO standards. One gets it by dividing the diameter of the Gear by the number of teeth. Funny thing: if you multiply the module by pi, you end up with the circular pitch.
The module system is useful because of pi, which makes some other calculations about Gears simpler. The module grows directly with the center distance between axes and shrinks with the number of teeth.
To choose the right pitches, think about how your Gears must work. Coarse pitch with smaller numbers handles high torque at low speeds well. Fine pitch with bigger numbers works for weak torque and high speeds.
Generally, small teeth run more quietly and smoothly. Most folks follow this rule: do not use a Gear with less than twelve teeth.
Straight Gears have their own set of rules. Take the linear pitch that you measured, multiply by pi, and you find the diametral pitch. A pitch gauge truly is the best tool to identify unknown Gears, and although one could use a thread gauge incases of need, a real pitch gauge is what you truly want.
