[Ben_Edict]

The official tool is a rubber ring that uses friction on just the name ring. MicroTools has it on their site. If you can find something rubber that fits just inside the filter threads and doesn't touch the front element, it will probably work.

Most name rings use the filter threads, so clean these first with a toothbrush if they're dirty. From the photo, this name ring might screw into its own threads. A few times, I have used a few drops of WD40 in the name ring threads to help a stubborn ring turn.

The rubber ring is indeed the "official" tool to do that. But as Pentax sometimes glues those rings into place, it is absolutely impossible to move them with just the rubber ring. It is worth a try anyway.

Ben

[richard64]

Have you tried gentle warming? Leave it on the back of your tv or computer for a while.
Maybe even in your pocket. It might help.

"Is that a Takumar in your pocket, or are you just pleased to see me?"

Richard

[TimB]

The official tool is a rubber ring that uses friction on just the name ring. MicroTools has it on their site. If you can find something rubber that fits just inside the filter threads and doesn't touch the front element, it will probably work.

Most name rings use the filter threads, so clean these first with a toothbrush if they're dirty. From the photo, this name ring might screw into its own threads. A few times, I have used a few drops of WD40 in the name ring threads to help a stubborn ring turn.

I had a lens like this with similar symptoms and no visible oil. Cleaning the blades had no effect. I thought the mechanism just behind the mount had too much friction. I used a few drops of WD40 there and it fixed the slow aperture. The lens worked for months that way before I was comfortable selling it as a working item.

Thanks for the WD40 tip.
I have tried a home made rubber tool, but the plate barely moved. I think it's a little too cozy in there for a rubber tool.
I'll have to resort to drilling, when I have time.

[georgweb]

Tim,
more talking from my side but hope to cut your net time spent on this :-)

Lighter fuel through the back:
If it's true that you only have to unscrew the back lens unit to get access to the blades I'd try this first cause it saves so much time.
Then, get some good lighter fuel like 'zippo', some residue-free cotton swabs (non-fuzzy), and do the aperture cleaning starting with the soaked swab on the fully closed aperture, circling the swab around the outside (in the direction the swab is hopping down the steps, not up), ever opening up the aperture while moving the swab. Like this, you'll never run the risk of bending the blades.
You have to be patient with this and change between soaked and dry swabs and snapping the aperture from time to time.
Finish with alcohol (pharmacy-quality 70% alc. / 30% aqua dest.) and the swabs.
After weeks and months the blades might get stuck again. Then, repeat the procedure.
This sounds complicated but it is very much less work than disassembling the whole thing.
The lighter fuel is a degreaser, whereas alcohol will take much more time to get the oil out.

Unscrewing name rings:
Take a back lens cap (like a PK-one), put double side sticky tape around the edge, degrease the name ring, unscrew!

Grease:
I have really worsened the situation with silicone grease, had some decent results with ball bearing grease and now try white lithium grease, which seems to be the official helical grease (no experience yet).

Arjay's hint to the classical camera forums is well worth, found all the invaluable infos there, and on the forum.manualfocus.org.

Happy tinkering,
Georg (the other)

[richard64]

Unscrewing name rings:
Take a back lens cap (like a PK-one), put double side sticky tape around the edge, degrease the name ring, unscrew!
[U]

Excellent idea! The only problem is that with a 49mm filter thread the PK cap is too big. But an M42 cap is ideal.

Richard

[Spex]

I have use Takumar back thread cap and rubber glove. Put the glove on the front thread/ring, and press with cap and twist it counterclockwise.