Installing lens on shutter- tightness question

[Wishegan]

I have a rodenstock 150 5.6. The rear element screws in fine until it reaches a point where there is resistance. I could keep tightening it, but it feels “wrong”. When do I stop tightening so it’s to spec? Is this normal?

Edit- copal 0 shutter.

[Bernice Loui]

Lens shutter retaining ring should be snug enough to prevent the shutter from moving while the shutter controls are operated/rotated and not much more. If the lens shutter retaining ring is over torqued that is when really bad stuff happens, like lens shutter getting stuck on.

~Hint, apply a tiny amount of anti-seize to these threads to prevent galling or stuck on lens shutter retaining ring.


Bernice

[Dan Fromm]

There should be a flat surface on the rear cell's shutter side, behind the mounting threads. The cell should screw in until the flat contacts the rear of the shutter's rear tube.

[Wishegan]

Sorry- to be more clear: the shutter is mounted well. The rear element is where the question lies.

[Wishegan]

Mr Fromm, so it should tighten until it stops firmly- that’s what makes sense. Thank you.

[Bernice Loui]

About the same as the lens shutter retaining ring, snug enough to assure the rear lens cell does not become loose under real world usage conditions. Too much torque can cause the rear lens cell to get stuck on to the shutter.

Bernice



Sorry- to be more clear: the shutter is mounted well. The rear element is where the question lies.

[Wishegan]

About the same as the lens shutter retaining ring, snug enough to assure the rear lens cell does not become loose under real world usage conditions. Too much torque can cause the rear lens cell to get stuck on to the shutter.

Bernice

So it not picky if it could be tightened another turn or two, as long as it doesn’t unscrew?

Edit: because it spins on fine for many turns. Then it has resistance, but I can still turn it more. I don’t want to break something.

[Bernice Loui]

Once the threads are seated (resistance to further rotations), small fraction of a turn is enough. The metal is being stretched once the threaded parts seat as more torque is applied, that is when really BAD stuff happens.

Bernice




So it not picky if it could be tightened another turn or two, as long as it doesn’t unscrew?

Edit: because it spins on fine for many turns. Then it has resistance, but I can still turn it more. I don’t want to break something.

[Doremus Scudder]

If the threads on your rear element have been damaged and the element will not screw in easily and seat securely all the way down on the seat, it will not be at the proper spacing for optimum optical performance. The rear elements on all the lenses I have screw in easily until they hit bottom and stop, clearly and unmistakably. It seems to me that the threads on your rear element may be damaged and keeping the element from screwing in easily all the way.

If you can seat the element without using too much force, then that would be fine. However, if you think that you need excessive force to get it to screw in all the way, you really need to take or send the whole lens to a reputable fine machinist/shutter repair person and have them chase the threads clean so that the rear element screws in easily all the way.

Best,

Doremus

[Wishegan]

If the threads on your rear element have been damaged and the element will not screw in easily and seat securely all the way down on the seat, it will not be at the proper spacing for optimum optical performance. The rear elements on all the lenses I have screw in easily until they hit bottom and stop, clearly and unmistakably. It seems to me that the threads on your rear element may be damaged and keeping the element from screwing in easily all the way.

If you can seat the element without using too much force, then that would be fine. However, if you think that you need excessive force to get it to screw in all the way, you really need to take or send the whole lens to a reputable fine machinist/shutter repair person and have them chase the threads clean so that the rear element screws in easily all the way.

Best,

Doremus

Thanks. I believe I can see a rough little bit at the last thread. I’m discovering a lot of problems with my favorite online used retailer. I’ll have to search out a machinist. 225991