1. Start by drawing a shape like the one on the right. To help you, make sure the Rulers are visible (VIEW...Rulers) and drag in a couple of guides.
The three circles are made by using the Ellipse Tool with Shift held down to create perfect circles. Tip: If you place your cursor exactly where the guides cross and hold down Shift and Alt. and drag away from the centre, your circles will be perfectly 'centred'.
This will help you to draw the main circle and the central circle. Draw a smaller circle above the centre point and the topmost shape (which will become the 'teeth' of the cog wheel) is drawn by using the Rounded Rectangle Tool .