Film-Tech Forum ARCHIVE: Unscrewing jammed lenses

This is topic Unscrewing jammed lenses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brad Miller (Member # 2) on 01-27-2003, 03:21 PM:

I loaned out some lenses and a prime w/Magnacom came back screwed together, no wait, jammed together. Looks like the threads were not lined up squarely and someone forced it. Fortunately it looks like there was only a couple of turns to it, but I can't get them to break loose.

Anyone know of any tricks for this that won't damage the lenses?

Posted by John Pytlak (Member # 331) on 01-27-2003, 03:42 PM:

Mild heat (e.g., a blow dryer) might help. Part of the trick is getting a good grip on the two halves stuck together. Maybe try those rubber grippers used to open stuck jar tops?:

Jar Opener

Jar grips

Twister Jar Opener

Posted by James Pope (Member # 1189) on 01-27-2003, 04:31 PM:

Dosnt Heat cause metal to expand? wouldnt you try getting it cold? causing it to contract. just a tought...

Posted by John Hawkinson (Member # 1135) on 01-27-2003, 04:36 PM:

Since you have access to the outside, you want to apply hear to expand the outside and hope you can do so without it transferring too much to the inside. So the outside expands and the inside stays the same, and then you can remove them.

--jhawk

Posted by Randy Stankey (Member # 64) on 01-27-2003, 04:48 PM:

Try a "Grip Wrench". You know those rubber strap wrenches you can buy on TV.

Use two of them in opposing directions. (They come in sets.)
It may bung up the threads if you force them but I think it's safe to assume that the threads are already beat up if somebody cross-threaded them so tightly you can't get them apart. You may be able to use a thread file to clean up the threads again. (If you can find a thread file with the right pitch.)

Posted by John Walsh (Member # 168) on 01-27-2003, 04:55 PM:

I think some lenses have threads 32 per inch, others have 36 per inch.

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-27-2003, 05:06 PM:

As a last resort, put some rubber bands around the end and clamp it in a vice. Don't break the lens. [Frown]

Posted by Serge Bosschaerts (Member # 298) on 01-27-2003, 05:19 PM:

A vice will do the job put don't put to much pressure on the lens.
I used this method to get an Isco lens off a hypergonar scope lens and result was : I got them seperated but the ring in front of the Isco was disformed and useless, fortunely the lens fitted on a Isco Scope lens without this ring. [Roll Eyes]

Posted by Stephen Furley (Member # 1277) on 01-27-2003, 06:29 PM:

Try putting some rubber bands around the lenses, to get a better grip. I would avoid things like vices and lathe chucks if at all possible, it is very difficult to feel how much force you are applying, and very easy to damage the lens.

A lubricant can help, but you need something very light, like watch oil, or even kerosene or Diesel fuel. Apply a tiny amount, using a very small paint brush, or the tip of a pencil, at various points around the threads, and wait. As it is such a light oil it will be drawn in between the threads by capilliary action. If the parts are aluminium, enen a few small drops of soapy water may help.

As someone else suggested, moderate heat may help.

I have had jammed optical threads, on several occasions, and have always been able to release them by these means. It does sound as if you may have two threads with slightly different pitches, the clearance between the threads is enough to be able to screw them in one or two turns, but then they jam.

I have also had this problem when cutting threads myself, and trying them for fit, and the fit was slightly tighter than I thought. Aluminium threads are more prone to jamming than brass ones.

Posted by Steve Kraus (Member # 476) on 01-27-2003, 07:14 PM:

Don't they make the Cap Snaffler anymore? [Confused]

"And it really, really works!"

Posted by Adam Martin (Member # 641) on 01-27-2003, 07:22 PM:

I use this on pulleys:

I wrap a couple of layers of old belt around the pulley and then attach the wrench.

It may work for you.

Posted by John Hawkinson (Member # 1135) on 01-27-2003, 08:34 PM:

Vice grips and similar tools really should be the last resort. It's very easy to damage something. A little bit of heat and lubricant, and some friction-gripping device should work wonders.

If it wasn't a lens, hot water is often a good choice.

--jhawk

Posted by Frank Angel (Member # 248) on 01-27-2003, 08:42 PM:

Whack the thing with a hammer like the popcorn guy would do. [Big Grin]

Posted by Gordon McLeod (Member # 33) on 01-27-2003, 08:46 PM:

I regularly use a pair of those vice grips to get old siezed lens apart with no damage
Lubricants are out as I have seen them through capilary action get back into the optics

Posted by Sam Hunter (Member # 1119) on 01-27-2003, 09:16 PM:

Brad, buy or borrow two of those strap wrenches and go to town on it. You get enough pressure on it and it will break loose.
Once you get it broke loose you will have it made.
If that doesn't work the I will be glad to explain how to pop it loose using two 5lb sledge hammers.

Posted by Steve Guttag (Member # 268) on 01-28-2003, 03:53 AM:

Oh my god...this is an old one...use two Century lens adapters (the 2-25/32 to 4" ones for the SA or JJ). They fit the lens "amazingly" well. The outside of the adapters give you good purchase to grab on to. Old Simplex G-2156 adapters work well too (the clamping style, not the current nylon screw style).

Using the adapters will not damage the exterior of the lenses and are often just laying around somewhere.

Steve

Posted by Adam Martin (Member # 641) on 01-28-2003, 04:06 AM:

What? Use legitimate parts? [Razz]

Posted by Stephen Furley (Member # 1277) on 01-28-2003, 06:56 AM:

Gordon, I find lubricants are ok, and have used them several times myself, so long as only the slightest trace is used it doesn't get onto the glass. Certainly, they shouldn't be applied with an eye dropper, or anything like that, which will put far too much on. It's a good idea to wipe the threads with a lens tissue afterwards.

There is an American company, I think the're called Micro Tools, which exhibits at a large camera fair in London each year. They sell devices made for the purpose of gripping lenses, which work well, without distorting the rings, marking the surface, etc.

Posted by Mark J. Marshall (Member # 1409) on 01-28-2003, 09:21 AM:

Try some Film Guard. [Wink]

Posted by John Pytlak (Member # 331) on 01-28-2003, 09:30 AM:

I would hesitate to use any liquid lubricant or release-agent on a lens. Even a small amount getting into the optics would likely cause haze and flare, especially when vaporized by the radiant energy/heating of projection.

Posted by Mark J. Marshall (Member # 1409) on 01-28-2003, 09:32 AM:

Yes, that was a joke. Sorry, I know there are lots of newbies and lurkers out there, and I should have added a disclaimer. Don't try that at home!

Posted by Brad Miller (Member # 2) on 01-28-2003, 12:25 PM:

Thanks for all the tips. I've already tried everything here except for the vice grips and using the Century collars. I'll try the collars first, as I am afraid I will do some damage with the grips. (Although the rubber bands are a great idea. [Smile]

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