Lens Helicoid Reassembly

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rolleicaster

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Hello my friends -- I throw myself upon your mercy.

I disassembled my Elmar 50 3.5 for the first time in order to clean and relubricate the threads. It's just a simple screw, right? WRONG

Naturally I did not mark the position to re-seat the thread. I've been going at it for an hour, but I cannot get the thread to purchase in ANY position, much less the right one -- it never seems to want to seat.

Does anyone remember or have recorded somewhere the correct position to begin threading in the helicoid on one of these? Or is it always different?

This is a "red scale" coated Elmar if that makes a difference.

Thanks in advance, I'd love to not have to embarrass myself in front of a technician...
 
rolleicaster said:
Hello my friends -- I throw myself upon your mercy.

I disassembled my Elmar 50 3.5 for the first time in order to clean and relubricate the threads. It's just a simple screw, right? WRONG

Naturally I did not mark the position to re-seat the thread. I've been going at it for an hour, but I cannot get the thread to purchase in ANY position, much less the right one -- it never seems to want to seat.

Does anyone remember or have recorded somewhere the correct position to begin threading in the helicoid on one of these? Or is it always different?

This is a "red scale" coated Elmar if that makes a difference.

Thanks in advance, I'd love to not have to embarrass myself in front of a technician...
Click to expand...
Some helical restart easier than others. The critical thing is not to force them. The more damaged the thread starts are the harder it becomes to start them.

Because the fit is precise it's necessary to also keep the ends of each unit parallel to the other as the threads are started. Some are very fine, so the slightest amount of tilt can see them steadfastly refuse to cooperate.

I've had similar issues to you in the past (albeit not with an Elmar, so I can't be specific about that, sorry). All I can suggest is to clean the threads scrupulously in the first instance. The smallest piece of grit or even lint can be problematic. I'd toothbrush the threads with solvent, chase them out with toothpicks (watch for tips breaking off), or even a lint-free cloth and fingernail or dental pick, and then inspect the thread starts with a loupe.

As long as the starts have not been forced, if there's damage, you may be able to clean gently them up enough with Eg a dental pick so that they will engage more willingly. Go easy. Threads are small, probably brass ot other soft metal, on that lens, and easily scratched up. A gentle touch is needed to scrape the starts closer to original profile without gouging the surfaces. This would create raised edges inside the threads, and that won't help the feel of focusing the lens. Magnification is essential, to see exactly how you are altering the material.
 
They can be really tricky to screw back on sometimes. You also need to know in what position or it won't align with the rest.

My tip is to thread it on very carefully. Starting by turning it counter clock wise (the wrong way) until you feel a faint click, that's the position it's going to enter the threads. Very gently turn it back and forth until it enters the threads. If you are at it for too long and use to much force you can damage the brass threads.
 
I have done this in the past. Just leave it for a few days and then go back to it.

Don't worry if you get it wrong first time, once you get the knack working by trial and error is easy (or at least an easy way of passing time).
 
Grease the threads well - after cleaning them with a toothbrush and solvent - with fresh, clean ball bearing grease. This will protect the threads and will make the focusing movement silky smooth. Never force anything. Puzzle it out with patience. Remove the long screw, but leave the short screw were it is. After you've found the right track, replace the long screw.


Erik.
 
Marking where the thread comes off is the way to go before dis-assembly but sometimes we forget to do this and it is not a big problem with the usual multi-start threading used in lenses...like others said, lube the threads and don't force anything..trial and error will eventually lead you to the correct start, just have patience and don't get flustered.

Best advice given here is to set this job aside and try again later when you are in a better frame of mind.
 
One technique that I have used in the past to get the correct thread start point with trial and error is to mark each start point on the multi-thread with a Sharpie that has failed to put the lens in proper order so you don't repeat it again. I use a magnifying loupe to properly see the thread start point. This can be time consuming but eventually you get to the right start point.
 
Make sure your grease isn't too thick or you're going to notice that the focusing throw is very smooth but also stiff and you'll have to do it again. These days I repair motion picture lenses (usually much finer threads) with 90wt hypoid gear oil applied by a small brush, thread by thread. As well as the threads, make sure to lube any lens assemblies that slide past each other like keys which prevent the whole assembly from rotating.

Phil Forrest
 
Summicron collapsible front barrel reassembly help needed

Summicron collapsible front barrel reassembly help needed

Hello, hoping for some advice here. I unscrewed the front optical barrel of my 5cm Summicron collapsible lens in order to clean some haze from the elements adjacent to the aperture blades. So far so good, it was easy to simply unscrew this unit from in front of the aperture ring.

The problem now is that after a successful clean, when I come to re-screw the front optical barrel into the unit, it screws in cleanly from only one position, and when it's screwed in tight, the aperture indicator dot is about 120 degrees out, so that aperture adjustments no longer have the dot adjacent to the aperture number.

I didn't make any changes or adjustments to the aperture ring position. It seems that there is only one correct place that the barrel screws in - I have tried numerous times to start the screw from a different location (about 120 degrees further around), but no luck. So I am wondering whether I can adjust the aperture indicator position to line up with the dot again when the unit is screwed up. Or is there some other error I have made in the reassembly?

Thanks for any advice!
 
largedrink said:
... I unscrewed the front optical barrel of my 5cm Summicron collapsible lens in order to clean some haze from the elements adjacent to the aperture blades. ... when I come to re-screw the front optical barrel into the unit, it screws in cleanly from only one position, and when it's screwed in tight, the aperture indicator dot is about 120 degrees out, so that aperture adjustments no longer have the dot adjacent to the aperture number. ...!
Click to expand...
I'm sure this isn't the answer you're looking for, but find a good technician and have him or her deal with it. You've just demonstrated why you should not take apart your cameras or lenses yourself - unless you know what you're doing.

Actually, I've run into similar issues myself trying to "do it myself."

You could try Googling the issue - maybe there's a YouTube video on the subject.
 
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