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evn137

Frozen case

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Good day. I have an old Omega Electronic F300 that hasn't been serviced in a long while. It's not working. Attempts to open the case has confounded me. I have a professional case opener that resulted in gouging the back. The studs that go in the notches of the case back were firmly held in place but the case back would not yield.
I finally resorted to epoxying a nut on the case back. The junction between the case and the back was pretreated with penetrating oil carefully. The case was held in a vice with wooden blocks with powdered rosin. The result is the picture. I am open to suggestions/ideas on how to open this case.
 
 
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918d0f23928eba1390a6dcd0b11a6ca8.jpgce352bba5d3c20434c9752d918b95fee.jpg

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Warning:  I am NOT a horology technician but, I am experienced in tool & die making and have a good bit of background working with zero-tolerance (and negative tolerance) fixtures and the like.

Find a way to gently warm-up the case and as soon as that is accomplished, put an ice-cube on the back.  As soon as the back is cooled (yet the case is still warm) use your case opener.   Heating the case will expand it, cooling the back will contract it.  Hopefully this take you out of the realm of zero-tolerance fit.

Regards

 

Ray

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Warning:  I am NOT a horology technician but, I am experienced in tool & die making and have a good bit of background working with zero-tolerance (and negative tolerance) fixtures and the like.
Find a way to gently warm-up the case and as soon as that is accomplished, put an ice-cube on the back.  As soon as the back is cooled (yet the case is still warm) use your case opener.   Heating the case will expand it, cooling the back will contract it.  Hopefully this take you out of the realm of zero-tolerance fit.
Regards
 
Ray

Certainly worth a try. Thanks Ray.



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44 minutes ago, evn137 said:

Good day. I have an old Omega Electronic F300 that hasn't been serviced in a long while. It's not working. Attempts to open the case has confounded me. I have a professional case opener that resulted in gouging the back. The studs that go in the notches of the case back were firmly held in place but the case back would not yield.
I finally resorted to epoxying a nut on the case back. The junction between the case and the back was pretreated with penetrating oil carefully. The case was held in a vice with wooden blocks with powdered rosin. The result is the picture. I am open to suggestions/ideas on how to open this case.
 
 
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918d0f23928eba1390a6dcd0b11a6ca8.jpgce352bba5d3c20434c9752d918b95fee.jpg

I have used epoxy effectively in several cases. I use the JB Weld's ClearWeld quick-setting epoxy that comes in a dual syringe dispenser and has to be mixed immediately before use. Let it cure overnight (disregard that 5-minute claim). Using an adjustable wrench and increasing the pressure slowly it should begin to loosen. The only issue is that the epoxy has to be burned off with a pencil torch and afterward the caseback has to be scoured with teflon and metal cleaner to get the black stains out. It is extreme, but works.

J

 

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9 hours ago, evn137 said:


Certainly worth a try. Thanks Ray.



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To be a bit more specific, as a reference point, if that case is made of 316 Stainless and if it's 1.75" (44.45mm) diameter then, heating the case to 115F (46C) and cooling the back to 45F (7.2C) will give a 0.002" (0.051mm) clearance in the threads.  This is a rough approximation but should be close enough for this application.  Please see this chart for other coefficients. http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html  There is a simple calculator somewhere on that page too.

Also, I understand how this may seem inappropriate for watches but, I would also put a couple drops of light oil on the seam where the threads meet.  Doing that in-combination with repeated attempts to cause thermal opposition (aka sweating) in the fitting of the threads is a trick used in Tool, Die and Fixture making on a daily basis...

How you go about heating the case to 115F ????  Beats me!  That's up to you.:startle:

Ray

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115F is easily done with a hairdryer for example. Should only take a few seconds.
Are you sure it's a screw on back ?

Thanks for the input. I was thinking of an oven with careful temp monitoring then set up the vice wooden block with the case opener . Then spray ethyl chloride on the case back for cooling. Will Also do the oil around the case/backing junction and let it penetrate maybe overnight before doing it.
Thanks for the input. I'll post the results.



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12 hours ago, frenchie said:

115F is easily done with a hairdryer for example. Should only take a few seconds.

Are you sure it's a screw on back ?

Yes, silly of me not to think of a heat gun or simple hair dryer.  In my usual endeavors, lightly heating something involves temperatures at a minimum of 450F which is about the lowest point of Martinsite when tempering ultra hard carbon or alloy steel.   I would urge however that the case must be thoroughly warmed, not just superficially warmed.  Spraying some aerosol coolant such as CO2 etc is a marvelous idea to cool down the back.

If I had a dime for every time I had to sweat-fit a negative tolerance part or use opposing thermal shock to get something apart, I could probably buy a very nice wristwatch.

 

Ray

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Ray, that's why I was thinking of an oven where I can preheat to 115 and leave the watch there for about 30 min. That should warm it to the core. Then install the case in a vise with wood blocks, apply the case opener with some torque, then spray the back with a spray coolant like ethyl chloride.


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My only parting thought is to put the watch in your case fixture, get it all ready and set then, shoot the coolant at just the back then, apply torque to loosen the threads.  Finally, the temperature of 115F was my idea based on the fact that most button-type batteries can handle temps up to 120F before leaking.  I'm assuming your timepiece still has a battery inside it.

Good luck!

Ray

 

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I just opened a stuck back in an old zodiac super seawolf that I had just about given up on getting open. I put it in a plastic vise that I use, attached my wrench as tight as I could, then heated the outer rim of the back with a propane cigar lighter typically called a torch lighter for just a few seconds, then quickly applied steady pressure, and it turned! The problem comes about when the old rubber ring turns to a tar like substance which effectively glues the back to the case. Melting it carefully this way can give you a few seconds to get the back started turning. I hope this helps someone else. Steve


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Oh yeah! Finally it opened. Thanks Ray. Thanks Frenchie.
It worked after 2 tries. First try, I heated the watch in the oven, then transferred to the vise block , mount the case opener carefully, apply pressure with the aid of a mill press, then apply some torque to open, then hit it with the coolant. Didn't work. The problem, getting it setup took time. Maybe I cooked it too much to.
The second time, it set it up ready to open position ( vice block, case opener aligned pressing on the case. Then I heated the whole setup with a heat gun, then hit the back with the coolant and it finally gave. I still had to open it half way using the setup since after cracking the case I still could not open it by hand. Again, thanks for the response . Pics enclosed.55631652b5b780c635fe8aa5c0f7a0cb.jpg3cc80a57858d281bf4c0662154174c14.jpg1c064a40b8188fab30d16165ee24d171.jpg




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I just opened a stuck back in an old zodiac super seawolf that I had just about given up on getting open. I put it in a plastic vise that I use, attached my wrench as tight as I could, then heated the outer rim of the back with a propane cigar lighter typically called a torch lighter for just a few seconds, then quickly applied steady pressure, and it turned! The problem comes about when the old rubber ring turns to a tar like substance which effectively glues the back to the case. Melting it carefully this way can give you a few seconds to get the back started turning. I hope this helps someone else. Steve


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Hi Steve,

Your right, the rubber gasket get very gooey ( described as tar ) when it ages. This apparently a common problem in Omega F300 among other things . I managed to open the case with help ( suggested technique ) from others who have gone down this horrible path.
Thanks for posting.


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Good news to hear the case is open now.  I suspect the expansion/contraction helped a little bit but, it seems the disintegrated gasket may have been acting as an adhesive; thus warming it up and softening it may have played a significant role in leading to success.  Also, the gasket may have been partially dissolved by the light oil that was intended to penetrate the threads...   In any event, mission accomplished.  Good work.   Man 1, Watch 0...  :D

 

Ray

Edited by RayCJ
typo

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