I needed a cog wheel image to apply as a bump map to my logo design so I had a little tinker in Gimp.
Here’s my process for making a cog wheel in Gimp.
Step 1: Draw a wedge shape.
Step 2: Mirror the wedge.
Step 3: Rotate it 7 times around the centre-point.
Step 4: Select a smaller circular area.
Step 5: Fill the circular area with black (using the ellipse selection tool + Shift + Ctrl to select from the centre-point). Select a smaller circular area and fill that with white. Repeat until happy with the pattern.