Seeing that the included addon script for making grears is broken in the 2.66a version, and not finding any others here, I decided to make my own from scratch and practice with the Cycles nodes. What I ended up with, being new to Blender and node editing, was rather pleasing to me.
The gears and associated materials are yours to do with as you please. Constructive criticism of how I used the nodes to make the materials are very welcome, I'd love to know better ways to do things :)
The leather material is from elsewhere on this site; thanks to "elbrujodelatribu" for a wonderful resource!
(The preview render uses an environment texture which is not included, but doing a search for free HDRi maps will result in many available.)
I admit I didn't even try changing the number of teeth :) Thanks for your reply!
Thanks for your credit! Your metal materials are very interesting. I'm not sure if you have to select "Experimental" in render panel to use bump displacement, but in my render those textures seem a bit different.
Yes, I used different lighting in the preview render than is what is provided in the .blend file (because I had no idea of the license of the HDRi texture), so bump textures look different because of the way the different light is hitting them. If you delete the emitter planes and use a HDRi texture for the illumination, you'll get closer to what I had setup.
Nice work.! I found in Blender 2.6a that the addon to add gears works at first wrong but modifying the number of teeth it functions fine. I.E.: adding a 12 teeth gear seems to be damaged but changing the teeth to 20, for example, goes well. Then you can go back to the original 12 teeth and they appear fine. At least it has functioned well for me. Hope it helps. Ah, what is not so well is that the gears are hollow. May be this is the problem the addon has and you are referring to.