Need disassembly help for Hexanon 52mm f/1.8

[guardian]

I currently have two of the subject lenses, both in need of cleaning. I cannot get either one sufficiently apart. Here is the situation:

I have been able to remove the first (i.e., front most) two elements from both lenses without destroying anything so far. Bad luck for me is that both need cleaning deeper than that, into the rear elements. One lens contains a very small bug. The other lens has just a smidgen of fungus. Both lenses are otherwise in decent shape. I could rescue them, I'm certain, if I could disassemble them.

In both cases:

With the first two elements removed, and with the cone-shaped front piece also unscrewed and removed, I am down to a rather broad, black, round metal piece which appears to secure the next lens element. There are two slots in this piece, 180 degrees opposed, leading one to believe it should unscrew. But I've applied a very large amount of torque to that end and the piece will not budge. I've tried several times.

What does frighten me is that I have found here and there a substance I can best describe as contact cement or contact adhesive. If the lens was assembled, at the factory, with this cement (or adhesive) on the threads it would explain the impossibility of unscrewing the stuck piece. I've also tried to unscrew the rear most metal ring which appears to be securing the rear most lens element. It, similarly, will not budge. And I have applied a very large amount of torque, to the point where I was fearful for the integrity of the (rear) lens itself (the lens is OK, though).

I hope somebody has disassembled one of these lenses and knows the trick which currently is eluding me. Only thing I can think of is to warm the lens a bit. I've not yet tried that.

Surely there must be a secret to further disassembly of these lenses . . . I hope!!

[guardian]

Well no replies but it's OK. I assume other Forum participants lack experience disassembling this lens, just as I do. It's tough.

Still, wanted to provide an update anyway for others, despite no success so far:

I can offer a couple of observations. It appears possible the rear lens assembly might have been assembled with a kind of locking substance on the threads. I'm not certain of this, though. I tried warming the lens prior to applying torque. No luck with that approach.

It's possible I need to apply a solvent to penetrate the locking substance, if it exists. Applying solvent judiciously with the rear lens set still inside the helical would be very tough, if not impossible. Thus, I'm currently trying to learn how to separate the front and rear portions of the helical, in order to free the rear lens assembly.

Good news is that I have not, so far, destroyed the lens as far as I know. An exception would be if this lens is sensitive to, or requires, proper collimation. But it's a very old lens and I believe it is spherical, so I have hope I'll be OK.

[Lloydy]

If I want to apply a solvent to a tiny area I use a small medical syringe. Also, heat from a soldering iron can help loosen tight screws and rings.

[guardian]

This is an update. I cannot believe how long this has taken. However, I took my time in an effort not to destroy the lens. So far, it is OK. Still, when doing this kind of work one never knows when the lens' end will come.

Anyway, this evening I was able to separate the helicoid. This allowed intact removal of the rear lens group, as I had hoped would be the case. How easy this must be for someone doing it for the second, or nth, time. But this was my first time.

There were three virtually invisible, small, screws visible from the front, inside the outer (black) ring. When I loosened those screws it became possible to separate the helicoid. They were embedded in grease and dirt, and it took me days just to see those small screws.

Things aside from the rear lens group were/are quite dirty and oily. It's going to require a bit of cleanup and then application of fresh lubricant.

The rear lens group itself, including the small dead black insect still resting comfortably inside and stuck to the lens, continues to be locked. It will not unscrew. Of course now, with the assembly free, attempts to unscrew things are far, far more straightforward than prior.

On recommendation from elsewhere I will be applying a solvent, most likely lacquer thinner, in an effort to break down whatever glue or locking agent Konica might have used during assembly of the rear lens group. I now have the thread access I need to be able to apply the solvent easily. I didn't have that access prior.

If solvent fails I might try warming the assembly. I need to do something to allow unscrewing the front of the assembly which currently is locking in place its front lens element, and trapping the insect.

I don't want to immerse the rear lens assembly because it contains a properly operating iris which could be damaged by immersion. So I must find a way to free the front and rear lens retainers which does not harm the iris.

Bottom line, it is good after too long to have the helicoid separated and to have the rear lens assembly finally free.