View Full Version : Removing a stuck nut...

Christopher Perez
11-Jul-2005, 09:31
OK. I have a small problem. A #0 Copal shutter mounting ring has jammed tight on the lens. Its backed part way out, leaving the lens on the lens board largely unusable. I suspect that a sliver of metal between the mount ring and the shutter threads is the source of the problem. And I'm concerned about stripping the threads on the shutter.

I have thought of at least two ways to remove the mount ring:

1) freeze the shutter to shrink the metal, heat the mount ring to expand just that one piece, and try to unthread the ring from the shutter.

2) using a jewelers file, cut the mount ring from the shutter.

What's the best way to remove the mount ring in a way that does the least damage to the shutter and mount threads? I can always replace the mount ring if needs be. Thanks for your thoughts.

M Brian Mills
11-Jul-2005, 10:09
Freezing the entire lens and then trying to heat only part of the lens could cause other issues with element separation and I would try to stay away from such practice.

Using a jeweler's file to cut the ring off could be a decent solution though you have the opportunity to muck up your threads. The file could then be used to repair the threads after the ring has been removed--If the ring is truly lodged *that bad* then the threads probably need to be cleaned up anyhow.

Emmanuel BIGLER
11-Jul-2005, 10:32
Christopher : did you try one of the rubber-clamps (similar to those sold by Micro-Tools) in a desperate attempt to screw/unscrew the ring ?
Now that it is located at certain distance from the board, if the ring is not too thin, you might have a better chance to grip it firmly with the rubber clamp.

Christopher Perez
11-Jul-2005, 10:48
The mounting ring is quite stuck. No forward or backoff motion is possible at this time without fear of stripping the threads.

Regarding the deep freeze: I would, of course, remove any lens barrels before throwing just the shutter into the freezer. The front group is removable. The rear group is tight, but might be removable.

So the bidding thus far is: jeweler's file.

11-Jul-2005, 10:54
I would hope thatChristopher would know better than to freeze the lens and then apply any heat...

If you can removed the lens cells, freezeing the shutter and then applying heat to the ring would help. Very few people have the equipment that would make this easy such as a micro-torch or even a large soldering iron.... You could possible apply drops of boiling water tot he ring with a eye dropper?

I might try a drop or two of some lubricant like WD-40 on the threads, then a lens wrench if there's room to fit it. It not, a large rubber griiper or piece of inner tube. Any form of pliers would make the problem worse... Give a good penetrating lubricant a try and move the ring back & forth to see if it will free up.

If the lens board is made of wood, you could also split that off to make more room to use a lens wrench. If it's a 'good' board, the cost of replacement may be as high as a new ring though...

If I needed to remove such a ring, I would split it using a Dremel with a cutting disc. This would cause the least harm to the shutter threads were you wind up going a bit too far. Using a file would be very difficult in such a tight space....

11-Jul-2005, 11:43
I'll agree with RichSBV. Use the Dremel tool with a cutting disc. But stop short of cutting too deep. Then use a screwdriver to fit the slot, and twist, to try and split the ring. If it doesn't split, use the Dremel again and cut a little deeper, and try to split again. Good Luck!

Christopher Perez
11-Jul-2005, 12:00
Ah. Dremel. Good idea.

I'll have to find a cutting disk that's fairly small.

The lensboard is aluminum.

Thanks to all!

Jim Galli
11-Jul-2005, 12:05
Chain saw sharpening stone for the dremel should work. Even if you go a tiny bit into the shutters threads it shouldn't cause any permanent problem.

Michael Kadillak
11-Jul-2005, 13:26
I would try a penetrating oil to see if that provides enough lubrication to the metal on metal contact point. If that was unsuccessful and I planned on keeping/using the lens in the future I would send it to Grimes or another mechinist and let them fix it for you. If the threads are mucked up, a machinist is in order anyway. Save yourself the aggrivation and the risk that you mess it up and contract it out.

Grimes assisted me with a delicate removal of a galled 24" Red Dot from its barrel mount that was a real bitch. They can apply tourque to members with specialized techniques in a very contraolled environment that have proven to work. Dremels and files are nothing more than hack jobs highly likely to cause more damage IMHO. Been there and done that.

Neal Shields
11-Jul-2005, 13:35
"heat the mount ring to expand just that one piece"

Anyone want to buy a Leica 135mm with a broken front element?

11-Jul-2005, 15:22
"apply tourque to members with specialized techniques in a very contraolled environment"... I knew this woman years back.... Oh, wrong forum ;-)

I do like the chainsaw idea! I'll have to sharpen mine up and try it out... Wait, did I read that right? ;-)

Seriously though. The Dremel is simply a tool. Any butchering that may happen can't be blamed on the Dremel. What we hope for is that anyone taking a Dremel to a camera part know what they're doing.

I've recieved some pretty bad jobs from 'pros' too. Which is why I have a Dremel...

One thing noone (including myself) has mentioned is the tiny metal filing that will be produced by either the file, saw or Dremel. Some precautions should really be taken to NOT allow them into the shutter. I would worry more about this than slightly cutting into the shutter threads. But the idea about using the screw drive to do the split before the shutter threads are reached is right on!

As with any camera self-repair: if in doubt, send it out...

Jeffrey Sipress
11-Jul-2005, 15:49
I own a precision macnine shop. I do these repairs frequently.

WD40 is a moisture displacer, not a lube.

If you are at all unsure about the results your skills will yeild, then bring it into a shop like mine (not an automotive shop). Or, sometimes you can apply just a drop of light lubricating oil, give it a minute to soak in, and try to work the jammed nut loose. I don't know how much force was applied to get it to where it is now. If none of this works, you may have to use a small abrasive cutoff wheel as mentioned. DON'T use a little grinding wheel like the chainsaw sharpener on anything made from aluminum. That won't work, and is dangerous.

Robert A. Zeichner
11-Jul-2005, 17:10
Christopher, is the ring visibly misaligned (at an angle that would lead you to beleive it is cross-threaded)? If this is the case, there is a technique I used in camera repair business years ago that might be worth a try. Get a wooden dowel a couple of inches long and about 1/4" in diameter and position it on the high side of the ring. With a very small 2 or 4oz hammer, tap the dowel and try to snap the ring back onto the proper thread. These rings are surprizingly able to "bend". Don't place the whole shutter assembly on a hard surface, but rather, use your lap as a workbench to avoid doing damage. Also, unscrew both the front and rear cells so you don't risk damage to them. If the ring isn't cross threaded, ignore the above and think about applying a little anti-seizing fluid like "Slide" to the threads. Then, assuming there is a spanner slot in the ring, get a small screwdriver (1/8" blade) and with that same hammer, attempt to nudge the ring in a counter clockwise direction to get it to unscrew. Now I do have one other question for you. Do you see a small locating pin protruding from the rear of the shutter surface that contacts the front of the lensboard? If you see one and there is no hole in the board into which it fits, that's maybe how your problem got started. I hope some of this is of help.

Bruce Watson
11-Jul-2005, 18:35
Two things to consider:

1) If you put the shutter in the freezer, the O. D. of the shutter will shrink. As will the O. D. of the locking ring. But the I. D. of the locking ring will in fact get bigger. Try it and see. This alone might be enough to get it moving again.

2) A strap wrench might give you enough leverage to move the ring. It the ring got stuck while you were removing it, then turn it in the opposite direction. This may help dislodge whatever junk is causing the jam. I suggest doing this after removing the unit from freezer. Best way I know to do this is to clamp the retaining ring in a vise and put the strap wrench on the shutter body.

Good luck. Please let us know what works for you.

Larry Smith
11-Jul-2005, 18:45
I agree with Jeffery-- use a small amount of penetrating oil. I worked in aviation instruments at least twenty years and from personal experience the stuck ring is not the problem. Anxiety on your part will ruin the lens. Put a small amount of oil on the ring and set it aside until late tommorrow. If it moves a little tommorrow drop on a little more oil. Do not try to unscrew it all at once. If it moves and gets tight screw it back in and add alittle more oil. Cutting it off is beyond last resort. Patience Christopher patience.

Calamity Jane
11-Jul-2005, 20:05
If it will not move at all in either direction it is almost certainly "askew" as Robert suggests. If you have a caliper, measure the position of the ring from the lens board at 4 points around the ring and see if the readings are identical - if not, it is askew and a gentle tapping on the high side should snap the threads back into engagement.

I have worked on a LOT of old machinery with stuck fasteners but have never seen a lens with enough corrosion to jam up threads. If there were thatmuch corrosion, it would be readily evident on all the threads. It is far more likely someone got it askew trying to remove it (or tighten it) with the wrong tools.

Robert C. McColloch
11-Jul-2005, 22:39
As an old WD-400 man (it'l fix anything!), just spray a little on and let it SOAK. Eventually, it will capillary into the thread and loosen it. Have patience.

Paul Fitzgerald
12-Jul-2005, 09:00
Hi there,

Oh, you guys are going to hate me.

Chris, remove the glass and stuff the rear of the shutter with paper towel to keep out the filings. Get yourself a set of needle drills and a pin vise. Drill a line of holes in the ring starting at the threads and work outward, then crack the ring and spread it with a screwdriver. Yes, you will nick the threads but this will do the least damage. Patience is a virtue with this. Be careful NOT to break the drill bit.

When in doubt, send it out.

John Berry ( Roadkill )
12-Jul-2005, 09:59
As a deisel mechanic, I've used door ease and beeswax as a lube. Heat it with a heat gun or microtorch. As a liquid it will penetrate and form a lube for the threads. If it has started to gall the threads your only choice is to cut the ring off as further turning will cause a lot of thread damage.

Neil Miller
12-Jul-2005, 13:47
Hi - I have had to do this, too. I cut the ring with a dremel - the disk was as thick as screwdriver blade. Before getting all the way through, insert a screwdriver and lever the ring - hopefuly it will crack and release without harming the threads.