Answered: Modifying gears and sprockets

Is there a limit to which you are allowed to modify gears and sprockets? I assume shaving the teeth of gears and drilling the square hole out of a sprocket is legal but can you cut a gear or sprocket to use its parts to make something totally new? I just wanted to double check before I allow this on my students robots. Thanks in a advance.

Provided no other rules are violated in the process, this is legal.