Picture of How to make gears easily

One of the most difficult and yet common mechanical systems is a gear train. A great way to transmit mechanical power from one place to another or to increase or decrease power (torque) or increase or decrease the speed of something.

The problems are always that to make efficient gears needs quite a lot of drawing and mathematical skill as well as the ability to machine complex shapes.

For a lot of amateur work it isn't necessary to have maximum efficiency and therefore we can get away with a much easier to make, even with hand tools, system.

A gear is basically a series of teeth on a wheel.


provides a very good explanation of how gears work and how to work out gear ratios.

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Step 1: Formula and Maths (the bad news)

Picture of Formula and Maths (the bad news)

Formula for drawing and making gear teeth are all over the web BUT they seem, to the beginner, very complicated.

from http://www.engineersedge.com/gear_formula.htm

So I decided to simplify the issue and it works very well at both large scale and small scale. At small scale it works best with machine cutting with laser cutters for example when very small gears can successfully be made this way.

Step 2:

Step 3: The easy way

Picture of The easy way

So how.
1. the shape of the teeth is simplified to be half a circle

Step 4: Working out the size of everything

Picture of Working out the size of everything

2.We can now easily sort out some simple maths to make our gear

  • a. How big/small do we need the gear teeth to be, (diameter) - The smaller the gear the smaller the teeth need to be.
  • b. All the teeth that are going to mesh, (connect),  together must be the same size so calculate your smallest gear first.

3. Lets start with a gear tooth size of 10 mm

I want a gear with 10 teeth on it so the circle will be 10 x 10mm round (circumference)= 100 mm

To draw that circle I need to find the diameter so I use a bit of maths and a calculator a divide the circumference (100 mm) by Pi = 3.142

This gives me a diameter of 31.8mm I can draw this with a compass and then fit exactly 10 circles 10mm diameter round it with my compass.

If your able this is easier to do with even the most basic drawing software. If your using software you should be able to rotate the tooth circle round the main circle and will need to know how far to rotate each tooth - This is easily calculated by 360 deg / the number of teeth so for our 10 tooth 360/10=36 deg rotation for each tooth.

Step 5: Making the tooth shape.

Picture of Making the tooth shape.

delete the top of one circle and the bottom of the next circle. To make this work out there must be an EVEN number of teeth

4. We have our first gear. This can be cut in wood or metal with basic hand tools, saws and files.

5. It is easy to repeat this process for any number of gears as we need them. Keep the tooth size the same and they will fit together.

Step 6: You have your gear

Picture of You have your gear

6 Because this semi-circle shaped gear tooth is easy to cut you can do it with hand tools, a sabre (jig) saw or even a coping saw.

In the past I have made a template of 9 or 10 teeth from plywood and use it as a guide for my hand router and cut the gear teeth with little trouble.

If you have access to a laser cutter these can be cut from 3 or 5 mm acrylic and work well down to very tiny sizes.

Step 7: UPDATE

Just to add this to these ideas. Some time ago i tried making simple plywood circles and gluing on the outside a cut down timing belt from a car. This worked as well and is a LOT quicker to do.

You need to select a diameter that will suite the teeth spacing on the belt. I elected to cut between 2 teeth and make my join there.

killercatfish6 months ago

This is great, thanks! I will try this design on my 3d printer. I am trying to use gears to help kids in 6th grade understand ratios and proportions with a hands on application. Love that it includes a lot of circle calculations. Any suggestions on simple applications of these gears?

You could always make a simple drive train, using about 2 big gears and 2 small gears to make a slow input into a faster output.

kimvellore1 year ago

I got the program Gearotic and it has changed the way how I draw gears it has made it so simple, Check it out.

protolabs3 years ago
if making gears is too difficult, you can use sprockets like I made here:

but good work rickharris
tilmen4 years ago
I'm intersted in making gears and I've read somewhere that gears are the hardest mechanical components to make without proper tools.Your instructable is good and teaching from this point of view.
rickharris (author)  tilmen4 years ago
Thanks - To make correctly shaped gears is a little more complicated - there are lots of on line calculators and explanations of why they are that shape.

This is a way to make gears at home that for low pressure system work quite well.

large size you can make with a drill and round file, smaller sizes really need some kind of machine to cut them. A laser cutter works very well as in my picture.

thanks again.
Nice article,

Just bear in mind, there are very good reasons why gears have the profiles they really do !
rickharris (author)  steveastrouk4 years ago
:-) Yes I know - BUT for much hobby use the sinusoidal gear if not heavily stressed works as well and is much easier to construct with very basic tools.

Remember for hundreds of years Windmill manufacturers got by with simple squirel cage and pin gears.
Jayefuu4 years ago
You'd like Mathias Wandle's gear generator Rick. Steve has it, it's brilliant.

rickharris (author)  Jayefuu4 years ago
Yes I have seen that and used it - Works great and his wood work is fantastic.

There are other sites that provide gear drawing software as well - I believe inkscape has a gear drawing engine in it .

This is just a very simple way for someone to do it with basic compass and pencil tools.
SWV1787 Jayefuu4 years ago
I'm a big fan of Wandle's site it is defiantly worth looking at
brunoip4 years ago
Very useful.-