Drawing gearwheels is a frequent task for a technical illustrator. This article shows you how to arrange the cogs on the diameter.

The cogs of a gearwheel are arranged over the compass of the gearwheel at regular spacings.
With some background knowledge it is easy for you to arrange these cogs quickly. First, you have to draw the root diameter, the outside circle diameter, and a vertical line from the center of the circle to its outside. Duplicate this line and pull it clockwise around the center, thus defining the cog.

Another line is then pulled into the opposite direction by the double spacing, thus defining the spacing of the cogs. In this example, we have chosen 5° (respectively 10° for the cog spacing) as the rotational angle and from this we get 12 cogs. Other angles result in different numbers of cogs. Illustration B shows a line spectrum of 30° altogether.
 

With the lines you have created you can now construct the cogs with the adherent cog spacing.


 
Now, rotate a copy of the cog and the cogspacing by the value of the total angle (here: 30°, illustration E). Repeat this until all cogs are arranged around the compass (F).