-) buy a special threaded tool to press the dent out of the ring
-) make yourself a useful tool
-) look at a rummage bin at a photo shop for used filters. If you are lucky you will find a filter with not only the same filter size but similar mounting for the glass. Then "just" exchange the filter glasses. Maybe you find even the appropriate filter...
HD is high definition, chiefly the polarising material sandwiched between the glass, very similar to what B+W Kasemann POLs use: it is colourless, extremely thin and very, very clear; this benefits digital shooters, not so big a deal for analogue. Not all polarising materials are or were ever created equal. The Chinese made polarisers are appalling, masquerading as "quality optics". Buy one and pull it apart and compare it to a B+W (though it's not recommended you pull one of those beauties apart! )
I've had perhaps 2 or 3 POLs with damaged threads over the years; they are routinely thrown out; damaged threads on the lens side will damage the lens threads; frontal filter thread damage is by and large inconsequential, perhaps not allowing a hood to be attached (unless a clasp type). A dent on the front of a filter proves it has saved your lens from the same thing!
Ok. So the thread that goes to the lens itself is fine. The front thread is the one that got dented. I can still attach my lens cap on it. In fact the lens cap was on at the time it happened. Whatever fell on it seems to have pushed in/down a small spot on the front thread so that it longer rotates. I can see a little dent on the part where the metal holds the glass in place.
damaged threads on the lens side will damage the lens threads; frontal filter thread damage is by and large inconsequential, perhaps not allowing a hood to be attached (unless a clasp type)
An alternative to trying to de-bend a threaded ring or to re-cut a damaged thread is to simply mill-off that damaged part. Would not look nice but most probably will come out as the technically better working solution.
An alternative to trying to de-bend a threaded ring or to re-cut a damaged thread is to simply mill-off that damaged part. Would not look nice but most probably will come out as the technically better working solution.
I wouldn't have a clue how to do that, I can't even trim my nails properly! But sounds just the bomb for those willing to tinker. But for me, if I bugger a filter, I buy another one, learning solidly from my mistake.