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HELP! My Nokton fell apart! (Sort of.)
Old 06-10-2014   #1
Johann Espiritu
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HELP! My Nokton fell apart! (Sort of.)



This week, while I was using my Nokton 35/1.2, the screws that hold the lens to the bayonet mount all snapped! Luckily, I was holding the lens while focussing, so it did not fall. I showed it to my local trusty camera repair guy, who said it would be a simple job to screw back on, if we could find the exact screws. Would you guys know where to get these?

Thanks, in advance!

Johann
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Old 06-10-2014   #2
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Your local camera repair guy is definitely right, but finding the screws could be a challenge. I'd recommend heading to your local hardware store, with the lens so that you may find the appropriate thread pitch. The screw lengths can be trimmed to the correct size, but you'll want to make sure that the screw heads are properly sized to the respective holes.
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Old 06-10-2014   #3
Harry Lime
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Why not just shoot Stephen Gandy an email and ask him for advice?

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Old 06-10-2014   #4
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Thanks, I just emailed him. Hopefully he'll have the parts or at least be able to point me in the right direction.

Quote:
Originally Posted by Harry Lime View Post
Why not just shoot Stephen Gandy an email and ask him for advice?

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Old 06-10-2014   #5
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Another member here had that exact same problem with his Nokton 35/1.2. His lens repair guy used the screws from an old Minolta lens (no idea which one) to repair the lens for about a 1/3 of the price he was quoted for the correct screws from Cosina.
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Old 06-10-2014   #6
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Quote:
Originally Posted by jonmanjiro View Post
Another member here had that exact same problem with his Nokton 35/1.2.
... that is not really inspiring confidence. If this happens while walking and carrying the lens using a neck or shoulder-strap ...
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Old 06-11-2014   #7
Johann Espiritu
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Quote:
Originally Posted by maddoc View Post
... that is not really inspiring confidence. If this happens while walking and carrying the lens using a neck or shoulder-strap ...
I know what you mean... and/but this is by far my favorite lens, so I'm in a bit of a conundrum. I'm thinking of getting this repaired and getting a V2 to use. Bummer.
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Old 06-11-2014   #8
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If your camera repairer does not own a set of screw gauges, you might have to pick another one who does. Or go to a watchmaker, optician or precision mechanic who can determine the size and pitch of the screws. Even if it should happen to be a custom thread or some ancient non-metrical standard (highly unlikely given a very recent mass-produced lens), it would not be a problem for them to re-cut a standard thread.

There are many online dealers around that will globally ship pretty much every standard screw within 24h, in packages of a hundred or less, for less than 20c each - so getting the screws would be trivial and reasonably affordable once you have determined the correct size.
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Old 06-11-2014   #9
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Wow - I'm genuinely surprised that something like this could have happened. Now I'm hesitant to purchase anything from the modern Cosina Voigtlander...

Did you feel that something was odd with the lens recently? Or did it just happen without any signs? Surely these things have to be designed with plenty of tolerance, and yet all of the screws broke at once.
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Old 06-11-2014   #10
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The other member who experienced the same problem has a chrome Nokton 35/1.2 as well. Maybe the problem is due to the extra weight of the chrome version compared to the black version...

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Old 06-11-2014   #11
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Quote:
Originally Posted by Johann Espiritu View Post
This week, while I was using my Nokton 35/1.2, the screws that hold the lens to the bayonet mount all snapped!
The lens that Jon is talking about was mine.

The problem that occurred was exactly the same. Suddenly, all of the screws snapped.

It was a chrome version of v.1, just like Johann's.

My local technician repaired it with screws from an old Minolta lens.
If necessary, I could inquire with him about which one.

Cosina Japan refused to deal with individuals and told me to contact Cosina's representative in France. The French representative did not answer my emails until the third try, and then only to refuse any help.

Stephen Gandy, to his credit, was willing to help, after a fashion, in spite of his suspicion of serious wrongdoing on my part.

Always ready to criticize myself before others, I let it go at that golden rule. But to be honest, I never treated that lens with anything but respect and care. It never underwent any kind of shock whatsoever.

At the time, I thought that perhaps it was due to some kind of stress induced when the bayonet was removed and replaced again (for 6-bit coding by John Milich). But now seeing Johann's lens experience exactly the same problem in the same way, it sounds very fishy to me.

I think it is important that both Cosina Japan and Stephen be informed of this problem. It cannot be coincidence. At the same time, there is no need for alarm or overgeneralization about a manufacturer's QC.

The v.1 35/1.2 is a wonderful lens that compares favorably to anything at any price point.
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Old 06-11-2014   #12
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I suspect the same thing as @jonmanjiro - the added weight of the chrome might have been too much stress on the screws. They should be made out of titanium!

Thanks for the tip @noimmunity. I found four screws from an old Minolta zoom which fit perfectly. I need one more, as the Nokton requires five. I did test it, and the focus and everything still works fine. I too treat this lens (it's my favorite) with lots of care and never abused it , and until now, never had any problems with it. Neither do I have any problems with any of my other Voigtlander products.

I hope Stephen is able to send those extra screws, though...

Cheers,

Johann
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Old 06-11-2014   #13
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Quote:
Originally Posted by noimmunity View Post
At the time, I thought that perhaps it was due to some kind of stress induced when the bayonet was removed and replaced again (for 6-bit coding by John Milich). But now seeing Johann's lens experience exactly the same problem in the same way, it sounds very fishy to me.
It might be interesting whether Johann's lens had also been worked on previously - the flaw sounds as if all screws had been tightened past their permissible torque, which is a issue with many third party repairers. Quite a few of them don't own torque tools at all, and even if they do, they might be ignorant regarding the torque specs for that lens. Applying the torque appropriate for a plain steel screw to stainless, or not cleaning out a thread filled with hardened screw fastener are quite likely to damage the screw.
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Old 06-11-2014   #14
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Quote:
Originally Posted by sevo View Post
It might be interesting whether Johann's lens had also been worked on previously.
My lens has actually never been worked on, so that wouldn't have been the culprit. I'm thinking now that it's possible that the screws didn't all snap at the same time - and it was only when the last one popped that the lens mount finally gave. Again - it's good that I was holding it at the time!
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Old 06-12-2014   #15
Johann Espiritu
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Quick update: The Voigtlander dealer in Hong Kong (amd currently in Manila) can send me the screws for US$35. Seems like a lot to pay for screws, but at this point, I don't have much of a choice!

Thanks for the info above, guys!
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Old 06-12-2014   #16
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Quote:
Originally Posted by sevo View Post
It might be interesting whether Johann's lens had also been worked on previously - the flaw sounds as if all screws had been tightened past their permissible torque, which is a issue with many third party repairers. Quite a few of them don't own torque tools at all, and even if they do, they might be ignorant regarding the torque specs for that lens. Applying the torque appropriate for a plain steel screw to stainless, or not cleaning out a thread filled with hardened screw fastener are quite likely to damage the screw.
Japanese manufacturers love their LocTite; it would not be surprising if a repairperson overtorqued screws that were actually supposed to tightened less but but glued. Loose screws can also get sheared when the pieces they connect slide against each other (as might be happening when you focus) - but most camera screws are countersunk.

But it could also be poor design and materials for the job. Is the flange keyed to the body of the lens? Or is it essentially free to rotate if the screws are out?

One thing that always amuses is that no matter how few Japanese companies are actually involved in making metal parts for cameras, no two screws are ever compatible.

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Old 06-12-2014   #17
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Quote:
Originally Posted by Dante_Stella View Post
Is the flange keyed to the body of the lens? Or is it essentially free to rotate if the screws are out?
With the screws removed, the flange is free to rotate, so the screws are the ones that hold it onto place.
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Old 06-12-2014   #18
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Great - I just picked up a chrome nokton and was thinking about selling my black one. This thread has me reconsidering that strategy.

My black nokton had to be repaired as well - the front half started to wobble and once that happened I couldn't focus it accurately anymore.
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Old 06-12-2014   #19
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I have same same front wobble as you yossarian123. It's finally gotten bad enough to affect focus so time to find someone to repair it here in the UK.
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Old 06-12-2014   #20
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Snapped? Or came loose? If they'd snapped, I'd have thought it would be Hell's own job to get out the snapped-off bit. I'm probably totally wrong, but I'm surprised.

Cheers,

R.
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Old 06-12-2014   #21
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Quote:
Originally Posted by Roger Hicks View Post
Snapped? Or came loose?
In my case, they snapped. All five screws broke into two, and all cleanly right below the screw head, and all right in about the same place.
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Old 06-12-2014   #22
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Quote:
Originally Posted by Johann Espiritu View Post
In my case, they snapped. All five screws broke into two, and all cleanly right below the screw head, and all right in about the same place.
Phew! Thanks for the clarification. Well, no, it wasn't really a clarification, because you were perfectly clear to begin with. I just found it hard to believe!

Cheers,

R.
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Old 06-12-2014   #23
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I had one screw break as I was unscrewing to take the mount off to send to John Milch for coding. I emailed Stephen to get one and he told me to get one from a camera shop. Seeing he is the Guy for Voigtlander and has a camera shop (I sent him a M4P for a CLA once), I thought it was rude. I emailed Don Goldberg and he sent me one , no charge, so don't hold your breath waiting for Sephen to respond

By the way, it was a black one, not chrome
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Old 06-12-2014   #24
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Disclaimer; I am not an engineer so I don't know how to calculate the stress on those screws but, I am a machinist with 23 years in the trade and those screws look very small for the weight of the lens. I don't mean to criticize Cosina but it looks like it could have been designed a little better.

I would caution against loctite or other thread lockers. If there is no loctite then the broken screw can probably be rotated out using a needle. If there is a thread locking compound it gets more complicated. In that case heat, perhaps from the tip of a small soldering iron, could loosen the locking compound and the the broken stubs unscrewed.

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Old 06-12-2014   #25
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Another thought. If someone figures out the size and pitch of the screw would they please post it here. Owners of this lens may want to buy a small quantity of these screws and replace them every six months or a year as a precaution.

Crack propagation in steel takes time and replacing the screws every so often might save a lens from a bad fall. Joe
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Old 06-12-2014   #26
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Frequently replacing screws is likely to make matters worse. Meticulous discipline when assembling heavy lenses to mounts seems to be a requirement, as the screws themselves are not at fault!

Standard 8.8 class steel (the one most screws you can buy at tool stores are made from) has a strength of 64kg/mm˛. Assuming five 2mm screws, each capable of 128kg (the threadless core of a M2 screw is approximately 2mm˛), we arrive at 600kg - that mount ought to be fit for lifting a small car. Even mild steel (or V2 stainless) would still have half to 3/4 that strength. And M2 is on the tiny side for a mount screw, I'd expect M2.5 to M3.2 (and possibly stronger steel), so the above figures are already pessimistic.

It obviously is not a matter of the screws, but of them having been damaged in manufacturing or maintenance. Screws of the above size are rated for 1-2Nm of torque (already easy to exceed), while medium strength (blue) Loctite is supposed to require around four Nm to break loose in a 2x3mm thread - so chances are that the screws literally get screwed when untightening them a single time. Memo to self: Thread holes ought to be cleaned and fresh screws used whenever replacing a screw on a mount (and there should be no or only the lightest variety of screw locker applied).
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Old 06-12-2014   #27
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Your calculations may be correct but they ignore some important realities. Were these screws carefully made and of the proper steel? What is the thread profile of the screw. If the threading method leaves a sharp V at the bottom of the thread that becomes a place for a crack to start. Were the threads cut or rolled? Proper torque is essential and may be one of the chief causes of failure. Crack propagation in steel is progressive so replacing old screws with new ones that have no cracks can be preventative maintenance. Threads like these should be able to be removed and replaced many times before wear on the internal threads becomes a problem. Five of these screws will not hold a small car. I doubt they would hold your weight. Joe
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Old 06-12-2014   #28
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Quote:
Originally Posted by lewis44 View Post
I had one screw break as I was unscrewing to take the mount off to send to John Milch for coding. I emailed Stephen to get one and he told me to get one from a camera shop. Seeing he is the Guy for Voigtlander and has a camera shop (I sent him a M4P for a CLA once), I thought it was rude. I emailed Don Goldberg and he sent me one , no charge, so don't hold your breath waiting for Sephen to respond
I received a reply from Stephen, but since I'd already found a source for the screws from Voigtlander HK, it was moot. If the HK thing doesn't work out, I will contact Stephen again, or maybe just ask him for extra screws.
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Old 06-13-2014   #29
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I used the Minolta "replacement" screws today, and the lens stayed intact. Still a bit nervous to walk around with it, but I guess in time the trauma of a lens snapping off with wear out!

I may take the suggestion of just replacing these screws every five years (I've had this lens for seven, so I'm using this as the basis of the MTF) as a precaution.

@noimmunity, how long did you have your lens before your screws snapped?
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Old 01-16-2016   #30
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UPDATE: The screws snapped again two weeks ago, and I put in new replacements. As I have started to lose confidence in using this lens often, I have decided to "semi-retire" the Nokton and use it for special outings only.

I really think that the extra weight of the chrome version is the culprit. As there are only five screws (my Leica lenses have six), I think the weight of the glass and chrome put too much stress on the screws. Maybe I need titanium screws - until then, the Nokton will be getting a lot less exercise. :-(

The good news is that I've replaced it with a 35 'Lux FLE. :-)
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