Gear generator
Spur gear generator
An involute spur gear from three numbers: teeth, pitch diameter and bore. The drawing and the price update as you type, and the gear goes straight to our laser. No CAD, no file.
Shown in Delrin (acetal), .125 in
- Outside
- 3.25 in
- Tooth size
- 0.125 in
Every gear here is cut to the same standard, so any two with the same tooth size mesh. Under 13 teeth, a gear runs rough against most others; the gear pair template checks a pair for you.
Gear basics
Two gears that mesh
Gears mesh when their teeth are the same size. A 24-tooth gear driving a 48-tooth gear, both with the same tooth size, turns the big one at half speed.
| Measure | Driving | Driven |
|---|---|---|
| Teeth | 24 | 48 |
| Pitch diameter | 3 in | 6 in |
| Outside diameterpitch diameter + 2 tooth sizes | 3.25 in | 6.25 in |
| Tooth sizepitch diameter / teeth | 0.125 in | 0.125 in |
| Diametral pitchteeth / pitch diameter | 8 | 8 |
- Speed ratio (driven teeth / driving teeth)
- 2 : 1
- Centre distance (sum of pitch diameters / 2)
- 4.5 in
More gear templates
Pairs, racks, planetaries and sprockets
Each one is checked to run: the same tooth form as this gear, with the teeth in contact counted before you can order.
Gear pair
Two involute spur gears made to mesh, from the teeth on each and one tooth size. Shows the ratio and how far apart to set the axles.
Gear rack
A straight toothed bar that turns rotation into a straight line, with mounting holes and an optional matching pinion.
Planetary gear set
A sun gear, planets and a ring gear that mesh around each other, with a carrier for the planet pins. Big reductions in a small, flat package.
Roller chain sprocket
A sprocket for #25, #35 or #40 roller chain, with a centre bore. Cut to the standard tooth form so stock chain runs on it.
Materials
What to cut gears from
Questions
Gear generator FAQ
- How do I make two gears mesh?
- Give them the same tooth size: pitch diameter divided by the number of teeth. Then set their centres half the sum of the two pitch diameters apart. The gear pair template does this for you: it checks the two run smoothly and gives the centre distance, with an optional plate drilled to it.
- What pressure angle are the teeth?
- 20 degrees, with an involute profile and standard tooth depth, the most common spur gear standard. The roots are cut the way a hob would cut them, so any two of our gears with the same tooth size mesh; check the tooth size and pressure angle before pairing one with a bought gear.
- How many teeth can a gear have?
- Between 8 and 120. Very small teeth are hard to cut cleanly, so the generator asks for fewer teeth or a bigger gear if they get too fine.
- What is the biggest gear you can cut?
- 10.5 in pitch diameter. Every part has to fit 23.2 x 11.6 in.