Taking a dent out of a filter ring?

Dave Dawson · Mar 6, 2009

I have a couple of large format lens's that have been dropped (not by me) and they have a flat dent on the filter ring. I realise that great care must be taken not to put too much pressure so that the balsam is disturbed. Any special pliers available?

Thanks Dave Dawson

Ian Grant · Mar 6, 2009

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

John Koehrer · Mar 6, 2009

Or a plastic tooth brush handle, as above.
It may help to have a piece of wood with a similar diameter to the ring to hold the lens in place. But I've never bothered.

ic-racer · Mar 7, 2009

Mico-tools sells a "Lens Filter Ring Vise" for this purpose.

keithwms · Mar 7, 2009

If you go to a professional machine shop, they will have a big die cutter for each filter size (unless they use one of the fancy computerized dohickeys that cuts everything from one precise blade). If the metal is soft enough then that might be able to expand it out for you. Patience is the key.

If a dent or crossed thread is really bad but localized to one part, what you could do is just dremel out that section (which exerts almost no pressure on the lens if done properly) ...and then the filter threads will still be able to grab.

I have made slip-ons out of the [inexpensive, flexible, good] mamiya hoods that work quite well on lenses with messed up filter threads. All I do is circumcise the threaded section on the hood and the slip the hood onto the lens, and just pull the hood forward when shooting. Actually some of my lenses are set up this way even if their filter threads are good b/c it is so convenient.

AgX · Mar 7, 2009

In case the thread has been misformed one could try using a segment with a male thread instead of that piece of wood.

Ian Grant · Mar 7, 2009

That's easier said than done

If it's misformed the male thread won't mate up with the female thread, you could end up with even more of a mess

Ian

AgX · Mar 7, 2009

Depends on materials... And you still can machine out that very part of the thread.

mgb74 · Mar 7, 2009

Anyone ever use the Micro Tools vise ic-racer mentioned: Dead Link Removed

Work well?

John Koehrer · Mar 8, 2009

Not for $36 + shipping. At one time there was a pliers with M&F threads on it. You were supposed to squeeze the handle to straighten the bent threads. I don't know how you cold get enough pressure to have any effect.

The vise might get you to the point where you would use the dowel or tooth brush handle to make the final adjustment.
The trouble with all of these methods is that they're not precise. You may straighten the filter ring but the threads may have closed a bit. When that happens I use a dental probe or scraper to modify the thread.
I've about 1/2 doz different scraping tools for this.

darinwc · Mar 9, 2009

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 · Mar 9, 2009

Ian Grant said:
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.

Taking a dent out of a filter ring?

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