I recently fixed two lenses from my collection which had dented filter rings using this $36 tool from Micro-Tools.
The tool didn't come with instructions but using it is pretty straightforward. As a precaution, I covered the front element with cardboard. First, I positioned the moving jaw of the tool on the dent and aligned the threads from the jaws of the tool to mate with the threads of the filter ring. Then I gently spread out the jaws of the tool to press out the dent. I cannot over emphasize going slowly but surely!
|Dent was between 10 and 11 o'clock|
impossible to fit a hood or filter
|After the procedure, a 46mm|
screw-in lens hood fits with
|Dent was between 3 and 4 o'clock|
|Not perfect but better than it was|
The tool has paid for itself ;)