Who Can Repair Lens Filter Ring Damage?

[Leigh]

The repair tool consists of two semicircular metal dies that can be forced apart by a threaded shaft.
The dies are threaded, to mate with the threads on the filter ring. This prevents damaging the threads.

In use, you align it at the deepest point of the dent, then move it back and forth slightly while expanding the tool in increments.
This forces the rim back to its proper contour without damaging the threads.

- Leigh

[Sevo]

Beware, these tools put a fair amount of stress on the front lens element, and may crack them (even more so the relatively large thin front elements on modern LF lenses). However the wood dowel method is not that much safer either. Personally I leave bent LF filter threads be and only use either method on them when I cannot avoid taking apart the lens for some other reason (haze, fungus etc.) - there are enough alternatives to attach a filter to a LF camera.

[RedSun]

My buddy slipped on a wet rock a couple weeks ago and dinged a filter thread on one of his Contax 6x6 lenses. Neither of us had a pair of pliers in our pack, and we were still a
week's walk away from the nearest road. He did it australopithecene style, and found a soft branch and beat on it with a rock. It worked, and he got his filters on again. Dealing
with another lens which actually fell in the creek was a little more complicated, but it's back in service now too.

Wow! I wish I could be this lucky. I do not know much about the Contax lens, but it sounds like the ring is soft. Also, if not done properly, the filter ring can be further ruined when trying to force on the filter.

[RedSun]

For this you need some lapping compound. It's an abrasive-filled, sulfur-containing high pressure oil that will gently cut away the binding metal without the parts not seizing: http://www.newmantools.com/clover.htm

McMaster carries this as well, but their page is not as descriptive.

Can you explain further? For such a big dent, the filter ring should first be removed. Then a metal clamp or press should be set or made to fit the diameter of the ring. The ring press/clamp is then pushed the filter ring and straighten the ring back to its position. Finally, the filter ring thread should be clear of any imperfection....

[Leigh]

This is probably the strongest argument for always having a filter on a lens.

People scoff at the idea of the filter providing protection, until they have to pay
to get a lens repaired, or forgo using filters due to a bent lens rim.

If you bend the front thread, just replace it.

- Leigh

[RedSun]

Beware, these tools put a fair amount of stress on the front lens element, and may crack them (even more so the relatively large thin front elements on modern LF lenses). However the wood dowel method is not that much safer either. Personally I leave bent LF filter threads be and only use either method on them when I cannot avoid taking apart the lens for some other reason (haze, fungus etc.) - there are enough alternatives to attach a filter to a LF camera.

The filter ring should come off before the repair is done. Or we risk more damages....

[Robert Budding]

I'd send it to real machinists:

http://www.skgrimes.com/

[Leigh]

The filter ring should come off before the repair is done. Or we risk more damages....

If you remove it, what will provide support during the re-forming process?

- Leigh

[normanv]

I bought a 90mm lens for a Mamiya RB67 cheap because it had a dented filter ring. I used the
old method of shaping a piece of wood to a close fit for the outside of the ring and another with
a curved end to fit inside and the bashed it with a hammer (actually I was very careful) After a
few taps I was able to screw the lenshood on. Cost, nothing!

[Steve Goldstein]

This is probably the strongest argument for always having a filter on a lens.

- Leigh

Some people don't want the extra glass surfaces in front of their lens. The solution I used was to get a junky old filter in the proper size and remove the glass. This provides filter thread protection without an added filter, just be careful about vignetting if it's a very wide lens. It's also handy for lenses where the front element is frightfully close to a mounted filter - the 110mm SSXL comes to mind.