Petri CC Auto 55mm f1.4 disassembly (I'm stuck)

[Mike Deep]

Time to take this saga into its own thread.

I nabbed one of these off eBay with an aperture stuck at f16. Disassembly went pretty easily, until I was left with the objective housing with both doublets and the aperture.

For whatever reason, the retaining rings for both doublets won't budge. At this point, I have tried:
-Friction (rubber) turning tool
-Strap wrench
-Spanner wrench
-Isopropanol
-Acetone
-Naptha
-MEK
-Oven @ 350 Fahrenheit
-Oven @ 500 Fahrenheit
-Freezer
-Percussive maintenance (Rubber hammer and wood block to distribute the load)

I'm about ready to give up, unless anyone has any other ideas I could try.

A stray observation too:
The bolt pattern for the Petri FT breech lock lug on this is the same as the bolt pattern on my Petri 55/1.8's M42 mount. Now, the 1.8's mount opening isn't big enough for the 1.4... But maybe the 135/2.8 is? Need a working 55/1.4 to try it, though.

[visualopsins]

Any ideas?

[RokkorDoctor]

Presumably this lens has a similar construction to the f/1.8 one taken apart on this web page:

http://eij485b.cocolog-nifty.com/blog/2020/04/post-08fcba.html

Here the writer states the front came off easily, using a rubber friction tool for the name plate and the spanner-wrench for the lens retaining ring.

Looks like the name plate & filter thread are one single piece that has an outside thread fit over a brass housing.

I would first try gentle circumferential tapping with a small jewellers hammer around the outside to break any oxide bond, and then try to "walk" it off; i.e. applying a counter-clockwise (unscrewing) force whilst also applying a clockwise "wiggling" force on the assembly. Easer to show to someone than to explain it though...