in this tutorial you can learn how to make a techno gear by Photoshop 7. Follow this steps:
1. make a new image
2. use rectangular marquee tools or press 'M' and draw a rectangular then hold SHIFT
    key and add more rectangular then hold Alt key to decrease your selection (like this):


3. press 'D' key for Default color and then press Alt+Delete to fill your selection by  black color.



4. press CTRL+D to deselect and goto FILTER > DISTORT > polar coordinates
    and select Rectangular to polar



5. press OK

you done!
you can add more details and text .
this is my sample:

 

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