I'd drill a couple of holes near the edges of the back panel, across from one another and clamp a couple of bolts in a vice so the ends fit in the holes and use either a strap wrench or a pipe wrench to "unscrew" the outer shell. Or maybe just one hole right at the edge and use a prybar to lever up the back panel if the two holes didn't work.
Edit, you try heating the back panel on the edges with a torch to soften the glue.
Thanks again for the ideas Bob-D659. I'll try this and when I get access to some sort of dremel or a drill.
The torch option would be the last one as I fear heating the lens too much.
I'll post my results in case someone (although highly unlikely :) ) is looking to do the same on his Durst plate.
Looks like that Latub was already buggerd by removing the bottom and gluing on a threaded plate. If you don't have a Durst enlarger and just want the lens, try popping out that glued on piece. Looks like it is just held on with epoxy. Or perhaps saw it off around the perimiter. Once you have the lens and the threaded plate out, you can probably just unscrew them by hand.
I think you're right ic-racer, that's what came out after all my questions to many professionals.
At first I asked myself how they could have screwed the glued piece without any handle or piece to rotate it.
Like I said, I'll try to burn the epoxy if the drilling doesn't work out.
Thanks for all your help !
I finally did it :)
After trying many methods and removing the glue (epoxy, araldit ?) the thing wouldn't disassemble.
So I took a hammer and a screwdriver and gently tapped in the "space" between the silver ring and the black cylinder until I could tear the ripped cylinder off. It was really glued so well that it wouldn't disassemble until I teared the whole parts away.
Here is a pic of the parts.
Many thanks to all of you !Attachment 60028
Congrats, that was not fun, but at least you now have a useable lens. :)