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Donyet
Tinkerer
Username: Donyet
Post Number: 4
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 22, 2010 - 11:58 am: | 
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I am trying to repair the shutter on a Yashica-Mat and the person who repaired it last glued the screws that hold the whole shutter assembly in with some sort of glue. They won't budge at all, and I'm in danger of stripping the heads on these brass screws. I've tried solvent, and I've tried heat from a soldering iron as someone who repaired aircraft instruments told me to do, but nothing has worked.
Does anyone know any other techniques? I really don't want to damage anything.
Thanks,
Alex |
Finnegan
Tinkerer
Username: Finnegan
Post Number: 44
Registered: 09-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 22, 2010 - 12:04 pm: |
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Try nail polish remover. If that doesn't work, try paint stripper. |
Donyet
Tinkerer
Username: Donyet
Post Number: 6
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 22, 2010 - 12:16 pm: |
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Hello Finnegan,
The solvent I tried was MEK, which is nasty stuff and eats into many things. I will try acetone (nail polish remover) next like you say.
Thanks,
Alex |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 156
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 25, 2010 - 09:25 am: |
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Nothing new about some camera and lens screws being locked with shellac at production level. Grind a screwdriver to be a precise fit in the screw-slot. And I mean exact and no compromises,
Trickle a little acetone on the locked screwheads. It will find its way into the most microscopic gaps but evaporates quickly so you must commit yourself to repeating every two or three minutes for about a half hour. Then leave overnight.
In the morning you should be able to break the stick of the screws provided you apply heavy axial pressure on your perfect fit screwdriver whilst seeking a snap release. However it needs experience to know what is the limit of reasonable untorque. Aged brass screws can be quite brittle and the heads may shear off. Better to repeat the acetone treatment for as many overnights as it takes. If you are patient, you'll get there.
There is another preparation which is valid in your particular instance - albeit that it otherwise has no place in a camera-repairmans's toolkit.
WD40 is sometimes an even better route than Acetone. It rather depends on just what locking sealant was used.
Best |
Glenn
Tinkerer
Username: Glenn
Post Number: 791
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 25, 2010 - 06:58 pm: |
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Unlike many sealants/adhesives dried shellac is not broken down by alcohol or acetone, it is merely dissolved back into solution. This means that unless the repeated applications of solvent have completely flushed the shellac away or reduced the concentration sufficiently, leaving the screws to 'dry out' overnight runs the risk of the screws still being locked by dry shellac. Removing the screws whilst they are still wetted removes all possibility of that 'snap release'.
Are you sure that this camera has actually had the screws locked in with sealant/adhesive? Common brasses age by a process called dezincification - the loss of zinc at the molecular level, this will not only cause the brass to become brittle but also cause the screws to lock up because of corrosion products. Application of a drop of acetic acid/strong vinegar onto the screw-head will loosen the screw by dissolving the corrosion products. |
Paul_ron
Tinkerer
Username: Paul_ron
Post Number: 221
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 29, 2010 - 05:28 pm: |
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If all else fails, undersized drill them out n chase the threads with a tap. |
Donyet
Tinkerer
Username: Donyet
Post Number: 8
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 30, 2010 - 11:18 am: |
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Hello all,
I'm pretty sure they were glued in with some sort of shellac, as I can see the overflow around the heads. I haven't tried the acetone yet, but will try it soon. I did try WD40 on them as well but got nothing to budge. The strong vinegar idea is also worth a try. I just have to be patient.
Thanks,
Alex |
Paul_ron
Tinkerer
Username: Paul_ron
Post Number: 222
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 30, 2010 - 04:14 pm: |
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If it is shellac, alcohol is the diluant. |
Donyet
Tinkerer
Username: Donyet
Post Number: 9
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, July 01, 2010 - 08:00 am: |
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Okay, they finally loosened. I had used WD40 and then MEK and went on a business trip for 6 days and when I got back they were ready to go. Since I had used both I'm not sure which one worked.
Now on to my next question coming up on this forum. How do I repair the shutter itself.
Thanks for all the answers on the screw question. |
