Taking a dent out of a filter ring?

[darinwc]

if the rim is thin enough, you can "roll" it on a hard surface. I have had luck with mamiya TLR lenses this way.
However most LF lenses seem to be overbuilt so as the filter rim is THICK.. How on earth they still mamaged to get so bent out of shape escapes me.

[Galah]

I've straightened the filter rings a few times using a hammer and a small piece of wood (dowling), not too hard so it damages the threads but enough to just tap the dent out completely. I have used extreme care, and the lenses were fine and filters could be used afterwards.

Ian

This is exactly what I have done.

in my case, I bought a second-hand zoom (Astron 80-250mm) with an aluminium tube/filter ring, which had two shallow v-shaped dings in the filter ring, so that the filter couldn't be mounted.

What I did was to support the mount (camera) end of the lens on a piece of plastic foam (actually, a duco-washing pad for the car) on the bench, while the filter end was suppported by a .25 inch thick piece of dense rubber mat. Using a short piece of "softish" wood trimmed to a 3/8th inch diameter round at the business end, I was able to knock out the dents with two soft taps from a small "soft" mallet: nothing to it! The soft wood "drift" ensured that the threads would retain their shape, and the rubber mat absorbed any surplus energy from the taps with the mallet, and protected the external finish of the lens-tube.

The filter fits perfectly.