Rear element stuck on lens, need some ideas to get it off

[peter.mod]

I need some ideas to get the rear element on my 150mm Xenotar unstuck. I'm a bit apprehensive with applying too much force as I don't want to damage anything. I've tried the following with no luck so far:

1. light heat with a hair dryer + moderate force with my hand
2. liquid wrench + moderate force with my hand
3. liquid wrench + light heat + moderate force with my hand
4. adjustable hose clamp with moderate tapping + heat

I didn't try one of those can openers as I've read they don't distribute force evenly and can damage things.

Not sure what else I can try that is the next least destructive method in terms of risking damage. I'm contemplating sending it out somewhere.

Thanks,
Peter

[Eric Woodbury]

I had an element stuck one time. My camera repair tech wrapped double-stick tape on the outer diameter of the element so he could get a secure grip. You can also wrap it on your hands if you can't find the room to stick it, or irregular shapes, etc. Good luck.

[peter.mod]

Thanks for the reply, Eric. Getting a grip is not an issue, I'm worried about bending the shutter housing with my other hand by gripping it too tight.

[jnantz]

Have u put the assembly in the freezer yet ? Sometimes that works ..
Old bicycle tire works great as a grip

[seven]

get a rubber wrench or better yet, two.

[Eric James]

I'd recommend the freezer approach. Put your lens in a Ziploc bag along with some type of rubber gripping implement (e.g. a piece of an inner tube, as suggested.) The plastic will protect the lens from condensation, and the rubber implement will help with gripping the element. Try not to squeeze the shutter housing from opposite sides; rather, try to evenly apply pressure circumferentially around the housing.

If the Ziploc bag is too slippery, risk the condensation briefly enough to get a better grip. Then put the lens back inside the bag with a desiccant cartridge once you've freed the element.

If the first attempt isn't successful, try a few cycles of heating then cooling.

[peter.mod]

I just managed to free it.

I used a hose clamp around the rear element with some Magic Wrap pipe sealing tape under the clamp to protect the metal. Then I hammered the screw on the clamp it with a heavy screwdriver, repeatedly using fairly strong hits. It loosened right after I passed the point where I felt comfortable hitting it.

Happy that's over with!

[Mark J]

Now check that all the shutter blades are still on their pivots and that the housing has not parted on one side.
I speak from bitter experience after someone helped me to get a dent out of the front filter thread on a Nikkor 210.

[Kino]

Wow! Was it dissimilar metal corrosion or simply over-tightened?

Might take an ever-so-tiny-spot of anti-seize compound and spread it all over the threads of the element and wipe off 99% to keep this from happening again.

I would use the graphite based anti-seize rather than the copper-based stuff.

[peter.mod]

Now check that all the shutter blades are still on their pivots and that the housing has not parted on one side.
I speak from bitter experience after someone helped me to get a dent out of the front filter thread on a Nikkor 210.

Yes, everything is fine, no sign of any damage. It was on a lens board, so I rested it on the table using the lens board and tried to minimize any force going to the actual shutter housing.