Thinking of permanently attaching an adapter to a M42 lens - looking for advice

[countzero]

So, I have a Super-Multi-Coated Takumar 135mm f/2.5 that I decided is one of the best lenses I came across, and I want to permanently attach and adapter to it, to get rid of the hassle. My steps will be:

A. (lens) jam the aperture pin in "closed" position
B. (adapter) remove the locking thingie (if there is one)
C. somehow permanently attach the two together.

My questions are:

1. What are the best methods to solve points A and C? The lens has an Auto/Manual switch.
2. Is there a way to replace the whole mount? (I have some cheap third party K lenses I'm willing to take apart)
3. Has anyone here done this? Anything I should watch out for?
4. Any other thoughts?

Thanks in advance

Andrei

[Ole]

I don't see why you would want to do "A". It's not necessary. The lens has the auto/manual switch - keep it in auto when you focus so that the aperture is wide open, push it to manual to stop down to your preset aperture to measure the light and take the shot. If you jam the pin, then you'll have to turn the aperture ring back and forth, and you cannot preset an aperture.

[Tom M]

Well, I would just use Loctite to keep the lens and adapter semi-permanantly threaded together.. Loctite will keep it together, though, if you ever did change your mind, you can (with some force) get them apart but it certainly will not come apart in normal use.

[bdann]

Not sure why A would be needed. I've never found any need to jam the pin shut.

I have just done this last week with an M42 Mamiya/Sekor 55mm lens. I removed the spring from the adapter and simply screwed it to the lens. I considered putting some loctite on the threads, but in the end decided not too. If you screw the adapter down tight, it won't come off without quite a bit of force.

What's more likely is for the adapter to accidentally disengage from the camera mount, since the locking pin doesn't engage with the lens. This can be overcome by drilling or filing a small hole in the lens where the pin makes contact, but I haven't tried this yet. The lens I did this with has a really stiff focusing ring, yet I can still focus without the whole thing falling off the camera.

I plan on converting all of my screw mount lenses in this manner, too bad the genuine Pentax adapters are $40+.

[countzero]

Thanks for all the replies. After tinkering with it, I found that just removing the spring does the job. The screw is stronger that the bayonet, apparently

$40? Wow, it's the first time something is cheaper over here. We get the original adapters (albeit rather scarcely) for $13 equivalent, from the official Pentax dealership

Anyway, thanks again, it appears the solution was easier and more convenient than I originally thought.

[Clem Nichols]

Originally Posted by bdann

Not sure why A would be needed. I've never found any need to jam the pin shut.



What's more likely is for the adapter to accidentally disengage from the camera mount, since the locking pin doesn't engage with the lens. This can be overcome by drilling or filing a small hole in the lens where the pin makes contact, but I haven't tried this yet. The lens I did this with has a really stiff focusing ring, yet I can still focus without the whole thing falling off the camera.

Countzero:

This is good advice. It's very simple to do, and has no adverse effect on the lens whatsoever. I did this on a Tele-Takumar M42 mount lens I had which otherwise had a tendency to want to unscrew from the camera when I was focusing it. The notch in the lens engaged only about 1/2 of the locking pin, but that made it easier to mark the exact spot on the lens to either file down or grind down with a rotary tool, and this was plenty to "lock" the lens in place on the camera. The most important thing, as has already been pointed out, is to remove the spring from the adapter before doing anything else.

CN

Attached is a picture of my lens with the adapter ring in place, showing the notch cut in the periphery of the lens base.