Jammed (process) lens - need your help

[Sanjay Sen]

Hi,

This relates to a JML Optical 305 f:9 process lens (in barrel): I was trying to separate the front and rear elements/sections of this lens, and managed to get it jammed. It is now unscrewed half-way, and I cannot get it to unscrew completely, nor can I get it back where it was to begin with. What should I do to fix this? (I don't really need to take the sections apart.) Is there a gel, or something else, that I can use to loosen the jam?

I was using my bare hands, and then gloves, but it's jammed too tightly for me to unjam.

Also, I am guessing that the extra spacing that now exists between the front and rear elements/sections will be a problem, correct?

Thanks for your help!


Best wishes,
Sanjay

 

[bdial]

You might try PM'ing Jim Galli. Worst case, he can apparently sell you a replacement.
Is there a set screw in the barrel acting as a stop?

 

[Dan Fromm]

Sanjay, as is, it is useless. Jim Galli is selling one right now on the LF forum, he's asking $85. Balance that against the likely cost of having, e.g., SKGrimes fix yours and don't forget to include the cost of postage both ways.

 

[Sanjay Sen]

Is there a set screw in the barrel acting as a stop?

I don't think so - I cannot even screw it back like it was.

Sanjay, as is, it is useless. Jim Galli is selling one right now on the LF forum, he's asking $85. Balance that against the likely cost of having, e.g., SKGrimes fix yours and don't forget to include the cost of postage both ways.

Oh, no! I wasn't planning on sending this to SKG. I was looking for a DIY solution, if there exists one.


Thanks to both of you for replying.


Best,
Sanjay

 

[JBrunner]

Last resort- put it in the freezer- get it pretty cold - not freezing- dip one end into warm water- immediately try to separate.

 

[Sanjay Sen]

Last resort- put it in the freezer- get it pretty cold - not freezing- dip one end into warm water- immediately try to separate.

If this works, wouldn't I be creating another problem with water getting in the lens?

 

[k_jupiter]

You don't want to do anything with warm water and this lens. I just looked at mine, you just want to put it in the freezer and see if that will allow you to have the play that lets it release. It's a simple thread, male on both outer sections, female in the middle section. Put a pair of gloves on pull it out when it's good and cold and twist.

You have nothing to lose. You might need the threads chased when you get it apart.

tim in san jose

 

[JBrunner]

If this works, wouldn't I be creating another problem with water getting in the lens?

If water can get in, it can get out, and as I said, last resort, there being nothing to lose at this point. Tim's advice is more sound, and perhaps water is best avoided in the interest of the balsam, etc. Warming one end with your hand might be a much better procedure. Making one part contract, and one part expand by using temperature is the general idea. Failing any of this, you can borrow my lens hammer. It always works.

 

[k_jupiter]

If water can get in, it can get out, and as I said, last resort, there being nothing to lose at this point. Tim's advice is more sound, and perhaps water is best avoided in the interest of the balsam, etc. Warming one end with your hand might be a much better procedure. Making one part contract, and one part expand by using temperature is the general idea. Failing any of this, you can borrow my lens hammer. It always works.

J,

No argument with your procedure, it's just that with a male/female thread in this configuration the heat should go to the center part. That not being possible, just getting it cold should provide enough separation to untwist this thing.

If that doesn't work, Sanjay Sen I'll give you 10 bucks for the lens, I could use a spare front element. *L*

tim in san jose

 

[PHOTOTONE]

He's dealing with a barrel lens here, so a little moisture inside is not catastrophic, as long as it is dried promptly. The only thing inside the barrel is the iris.

 

[mattk]

Not sure if I can picture your problem, but I once jammed a enlarging lens and someone on APUG suggest I place a wide rubberband (like the ones on fresh brocoli in the supermarket) around the lens to provide a better grip. Make sure its tight--I was amazed at the amount of torque I could impart over such a small area. Good luck!

 

[Sanjay Sen]

Nope, no luck. Four hours in the fridge, and it still wouldn't budge, not even with gloves on.

 

[John Kasaian]

How about rubber strap wrenches? I bought a set for about $5 at one of those import hardware stores. one on an element and one on the barrel would give you a a lot of torque!

 

[Murray@uptowngallery]

I have a 5-7/8" mystery lens in an Melles Griot Synchro Electronic #3 shutter. MG denies it's their lens.

I struggled with it forever trying to get the rear cell out, and one day instead of trying to unscrew it, I pulled (not terribly forcefully) while trying to unscrew it, it it just popped out.

Just a guess, as far as liquids go, a tiny amount of alcohol, if the threads are aluminum. Machinists like alcohol when machining aluminum.

If you have nothing to lose, a tiny tiny drop of Tap-Eaze or whatever it's called, a metal-working lubricant. Clean it off with cotton swabs ASAP afterward.

Have you tried a pair of latex 'dishwashing' gloves? Turns puny weakling hands into Gorilla Grips.

If saving the threads is not possible and it becomes evident you will never be able to convince a buyer the appearance doesn't affect it's function, and it's thus yours forever, and you get it apart improperly, I wouldn't be above sanding the threads on the offending lens cell (then cleaning them) and gluing it back, maybe contact cement, that would be solvent-releasable.

 

[k_jupiter]

How about rubber strap wrenches? I bought a set for about $5 at one of those import hardware stores. one on an element and one on the barrel would give you a a lot of torque!

Well John, in this case getting one wrench on the barrel without screwing up the iris mechanism is problematic. The outer part of the barrel is the iris adjustment mechanism and is, if not fragile, prone to being over torqued.
San needs to be careful or send it to a repair person. Problem is,it's not a valuable lens ( I don't think).

tim in san jose

 

[TimVermont]

Nope, no luck. Four hours in the fridge, and it still wouldn't budge, not even with gloves on.

Hi Sanjay,

I'd suggest finding a really cold deep freeze. If there is a commercial cold storage place near you, they may have a unit as low as -30. Bag the lens in plastic before putting it in the freezer. Leave it in overnight. Wear insulated gloves under rubber gloves when you try to get it apart. Getting it truly cold will maximize the contraction differences between the metals, and possibly give you a longer working time to get it apart. Good luck!

 

[resummerfield]

I've had similar problems where I was distorting the barrel by gripping it near the threaded portion. The more force I used the more I distorted the barrel, seizing the threads. My solution was to grip the barrel as far from the threads as possible.

Use a rubber strap wrench, or a sheet of rubber or a rubber glove, gripping it around the barrel, near the glass. Grip the other end of the lens as far away from the threads as possible.

Another possibility is to place the lens vertical on a rubber sheet, and apply downward pressure on the other end of the lens, in an attempt to screw the lens together.

 

[John Kasaian]

If you want to try the thermal thing, after freezing the whole enchilada, you might try heat ing the component with female threads with a blow drier or hot air gun?

 

[Sanjay Sen]

Thanks, guys, for all the suggestions.

One option I will probably try next is mounting the lens on a board to get a better grip, and then having another go at it - with latex dish-washing gloves, as Murray suggests. It's not an expensive lens, so sending it to SK Grimes does not make sense.

 

[c.d.ewen]

Sanjay:

Be careful, if you use the rubber strap wrenches, as they will exert a lot of inward pressure on the lens where the handle touches the lens, just as a pipe wrench would.

That said, I have successfully unscrewed lenses with a pipe wrench by wrapping the lens with many layers of electrical tape to absorb that oressure, and using my judgement as to when I was applying too much torque.

The last-resort method, which has never failed me, is to drill a hole in a scrap piece of wood so that the lens fits inside tightly. I then dribble some water unto the wood, causing it to swell and grip the lens evenly. At that point, you can use a big ol' wrench and crank it 'til the threads rip.

Charley

 

[resummerfield]

.....drill a hole in a scrap piece of wood so that the lens fits inside tightly......

Excellent idea! I would then cut a slot in the wood, reaching the hole, so you could squeeze the wood around the lens. Much like a ring spanner or filter wrench.

 

[c.d.ewen]

Excellent idea! I would then cut a slot in the wood, reaching the hole, so you could squeeze the wood around the lens. Much like a ring spanner or filter wrench.

If you can make the hole so that the lens *just* fits in (I use a lathe), there's no need (or room) to squeeze the wood. The object is to swell the wood fibers with water and create friction around the entire circumference, rather than have one area receive more compression than another. Done right, you'll have to carefully cut the piece to get it off the lens.

Micro-Tools sells a wrench, called a Dead Link Removed, which is basically a thick sheet of copper with a hole cut in one end and a slot running the length of the sheet. Squeezing the slot causes the hole to decrease in size and thus squeeze the lens more or less evenly from all angles.

Charley

 

[Murray@uptowngallery]

If a step closer to absolute zero is really necessary, a grocery store near me now sells dry ice (CO2).

Let's not go to liquid nitrogen...might crack something if rates of thermal expansion (reversed) are too different.

I think the smarter clamp/grip methods are the way to go. Archaeologists find lots of tools showing how smart our predecessors were without tool catalogs, but they've never found a refrigerator. Don't quote me on this.

 

[ChuckP]

If you haven't tried it you might want to put a block of wood across the front and give it a few light taps with a hammer. Might break something loose.

 

[freygr]

I have used a heat source to warm up the barrel and Ice to keep the stuck inside part from warming up to the maximize the difference in expansion.