Stuck Jupiter 8

[Daimon]

Hi all,

I'm struggling with one Jupiter 8 "Made in USSR" - cannot unscrew optical unit from main body.

Ended up stripping it from almost everything (including lenses and aperture), soaking it in isopropyl alcohol, soaking it in acetone - even putting it in ultrasonic cleaner with acetone. Nothing, no way to unscrew optical unit.

Photos of the state of disassembly (of course when trying to unscrew it I'm attaching top silver ring to have something to grab 😉 )

Any tricks from anyone?

 

[Sonnar Brian]

We've PM'd each other on this- and you've tried everything I use to unscrew the barrel from the focus mount.
Except One. And the only reason I can do this is because I have a lot of extra J-3 and J-8 barrels that can have better glass transplanted to them.
I cut it out, leaving the focus mount intact and able to take the spare barrel. Nasty, last resort, may get scrap metal, but worked for me.

Alternative, which I've also done: Build up the RF cam with Copper tape to correct back-focus. For front-focus, unscrew the rear group to move towards the image plane.

 

[Daimon]

Yep thx for all the tips! Other jupiter 8 I have unscrewed without any problems. This one - I'm close to giving up.

Copper tape might be good workaround for focusing itself but there are other problems to fix here as well:
- completely loose aperture ring - I won't be able to apply grease in a right place without unscrewing
- aperture ring is not matching with scale - as last resort I could just slightly drill new holes for set screws (tried just rotating the ring not minding the set screw places - they don't hold properly if they are screwed too shallow)

 

[Sonnar Brian]

I've tapped many, many holes to re-index aperture rings and focus rings. No Fun.
As an alternative to grease for the aperture- use scotch tape to build up the ring, to provide some friction with the focus mount.

 

[Ko.Fe.]

If you have e-stove with warmer part... Apply WD-40 where not unscrewing thread is. Wipe it off, wait an hour or so and warm up entire thing. Let it cool down, apply WD-40 again, leave overnight. Repeat the same until it let go.

 

[Daimon]

Success!



Baking in 250*C did not help itself. WD-40 neither.

But night in WD-40 plus 2 special rubber band car maintenance wrenches managed to unscrew it 🙂

 

[Sonnar Brian]

Congratulations! What was holding it in? Glue?

 

[Daimon]

Hard to tell. Glue was definitely coming out during ultrasonic cleaning in acetone but could not unscrew it after that using hands and silicone pads. Baking in 250 degrees later, wd-40 and still no success. Only when I tried car fuel filter wrenches it finally moved - and I really had to use a lot of torque, those wrenches are quite big. It might have been both the glue and "standard" seizing of threads.

 

[Daimon]

And done.

 

[Coldkennels]

And done.

View attachment 4824383

Very nicely cleaned up!

What did you polish the pitted aluminium with? My Orion could definitely use the same treatment.

 

[Daimon]

I have both Brasso and Eilfix 2000. They work fine for very light tarnish. Brasso is a bit more mild. In both cases finish ends up being a bit too shiny for my taste but don't have anything else. For deeper pitting multi-grade polishing will be required.

Maybe someone more experienced may suggest something?

 

[Sonnar Brian]

That looks good to me.

I do use silver polish- but prefer 3M Polishing Sheets made for fiber optic connectors. I've also used it for rough spots on the inside of focus rings and inner parts of the J-8 mount.