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Author Topic: Unscrewing jammed lenses Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 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?  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 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  |  IP: Logged James Pope Film Handler Posts: 31 From: world wide web, USA Registered: Mar 2002 posted 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...  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 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  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 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.)  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 01-27-2003 04:55 PM                     I think some lenses have threads 32 per inch, others have 36 per inch.  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 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.  |  IP: Logged Serge Bosschaerts Film Handler Posts: 70 From: Schoten, Belgium Registered: Jan 2000 posted 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.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 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.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 01-27-2003 07:14 PM                    Don't they make the Cap Snaffler anymore? "And it really, really works!"  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 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.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 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  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 01-27-2003 08:42 PM                        Whack the thing with a hammer like the popcorn guy would do.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 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  |  IP: Logged Sam Hunter Jedi Master Film Handler Posts: 779 From: West Monroe, LA, USA Registered: Jan 2002 posted 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.  |  IP: Logged

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