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01-04-2017, 07:39 PM   #1
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Cosina 55mm f/1.2 Loose focus ring

Hi All,

The focus ring on my cosina has come loose and is now free spinning. I tried using rubber stopper looking things (in the picture) to try and remove the front name plate but that thing isn't budging.



Does anyone know/have a link on how to disassemble this lens?

Thanks in advance.

01-05-2017, 12:54 AM - 1 Like   #2
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bonjour...j'ai eu le même problème avec un de mes M42 et après avoir essayé d'y mettre un petit peu de dégrippant de me suis résolu à pratiquer proprement et à la Dremel deux petits trous opposés de moins d'un millimètre pour pouvoir débloquer efficacement cette bague de finition. Cela reste très propre mais attention de ne pas déraper lors du perçage. Finition avec deux touches de marqueur noir et le tour est joué... ;^)...bonne chance et Bonne année

Last edited by dadoudenice; 01-05-2017 at 11:05 AM.
01-05-2017, 07:32 AM   #3
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@serothis...

Need any help to translate that last post ?
01-05-2017, 10:17 AM - 1 Like   #4
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Well, before you go ahead and drill two small holes in the trim ring (and I've had to do that before), don't give up on your rubber rings.

To enhance the grip, try pasting some small strips of double sided tape around the rim of the ring, or on something just about the same size. I've had excellent results with plastic caps of aerosol cans. With the tape and not having to press down so hard, the ring sometimes comes off surprisingly easy.

Remember, the harder you press, the more the sticky threads grab.

If all else fails, go with the advice of the previous poster, and drill those small holes to fit your lens pin wrench.

01-05-2017, 10:48 AM - 1 Like   #5
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Try looking under the rubber grip of the focus ring. The grub screws to lock the focus mechanism may be there.
01-05-2017, 11:00 AM   #6
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QuoteOriginally posted by Ontarian50 Quote
Well, before you go ahead and drill two small holes in the trim ring (and I've had to do that before), don't give up on your rubber rings.

To enhance the grip, try pasting some small strips of double sided tape around the rim of the ring, or on something just about the same size. I've had excellent results with plastic caps of aerosol cans. With the tape and not having to press down so hard, the ring sometimes comes off surprisingly easy.

Remember, the harder you press, the more the sticky threads grab.

If all else fails, go with the advice of the previous poster, and drill those small holes to fit your lens pin wrench.
Merci pour ce conseil ;^)))

---------- Post added 01-05-17 at 11:02 AM ----------

QuoteOriginally posted by jpzk Quote
@serothis...

Need any help to translate that last post ?
Ce n'est pas très compliqué : GoogleTraduction
01-05-2017, 11:45 AM - 1 Like   #7
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Focus to 0.6m. Look at the barrel of the lens that sticks out above the focus grip for one tiny setscrew in a recessed hole. On my lens this is above the 0.8m mark*. Loosen that screw a few turns - you don't need to remove it. Then that front barrel unscrews. You should see four screws that attach the focus ring to the focus helix. Tighten those.

The trim ring should have come off - it is threaded just like on a Pentax or Takumar, but this way is easier. I think there could be more pressure on the trim ring than in a Pentax or Tak installation, so more starting friction. Also the lettering is not engraved so the grip is not as good.

*It could be anywhere.

Last edited by Just1MoreDave; 01-05-2017 at 03:35 PM.
01-05-2017, 03:29 PM - 1 Like   #8
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The tiny screw. If you don't already have a screwdriver for this, look for an eyeglass repair kit in a pharmacy/drugstore/convenience/truckstop. Loosen it until the head is just flush with the outer surface of the focus ring. These screws are a pain to find and reinstall if you remove them completely.



The four black screws here, outside the front element and recessed, hold the focus ring in the aluminum focus helix are the ones to tighten. They look like JIS screws. If you don't have a JIS screwdriver already, you can probably get by with a Phillips #00 because you are tightening, not loosening. Just be careful - the Phillips only kind of fits so you can't apply too much force or have the screwdriver off perpendicular. A Phillips #0 will not work and most likely ruin the screw for any future use.



01-05-2017, 06:02 PM   #9
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QuoteOriginally posted by Just1MoreDave Quote
The tiny screw. If you don't already have a screwdriver for this, look for an eyeglass repair kit in a pharmacy/drugstore/convenience/truckstop. Loosen it until the head is just flush with the outer surface of the focus ring. These screws are a pain to find and reinstall if you remove them completely.



The four black screws here, outside the front element and recessed, hold the focus ring in the aluminum focus helix are the ones to tighten. They look like JIS screws. If you don't have a JIS screwdriver already, you can probably get by with a Phillips #00 because you are tightening, not loosening. Just be careful - the Phillips only kind of fits so you can't apply too much force or have the screwdriver off perpendicular. A Phillips #0 will not work and most likely ruin the screw for any future use.
This worked absolutely perfectly. Thank you so much. A few loose screws that needed to be tightened was all that was wrong...I also took a bit too much pleasure in disassmbling the lens then I probably should have.
01-05-2017, 07:02 PM   #10
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QuoteOriginally posted by dadoudenice Quote
Originally posted by jpzk @serothis...
Need any help to translate that last post ? Ce n'est pas très compliqué : GoogleTraduction
You cheated !

---------- Post added 01-05-17 at 09:06 PM ----------

Just1MoreDave saved the day!
01-06-2017, 07:17 PM   #11
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QuoteOriginally posted by jpzk Quote
Just1MoreDave saved the day!
Yes, I am awesome!

I think I got lucky and figured that out myself. Other lenses might have used any of the tricks mentioned here, like screws under the rubber grip.
01-06-2017, 07:56 PM   #12
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QuoteOriginally posted by Just1MoreDave Quote
Yes, I am awesome!

I think I got lucky and figured that out myself. Other lenses might have used any of the tricks mentioned here, like screws under the rubber grip.
Yes indeed !
We never know: I too have one of those and it is still very much in excellent shape (and performs beautifully) .... but this loose focus ring incident and "fix" could be useful one of those days. (hopefully not, but ... )
01-06-2017, 09:35 PM   #13
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QuoteOriginally posted by Just1MoreDave Quote
Yes, I am awesome!

I think I got lucky and figured that out myself. Other lenses might have used any of the tricks mentioned here, like screws under the rubber grip.
Be it luck or skill, sir, I owe you a beer.
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