Cyma, opening caseback

[WilliamK7]

I am sweating down my back. These two cases are defying all my efforts. See damage from previous attempts and now I have added on one watch.  

Apparently one is a pop-off cover and the other is a screw-off? Advice appreciated. Maybe a three-point caseback remover tool?

[RichardHarris123]

The second to last photo looks like a screw on. Superglue a nut to the back, put in a case holder and use a spanner to turn the nut. The nut will come off with acetone.  The other looks like a snap on, try a  one sided razor blade and work around the case. 

[ColinC]

I watched a YouTube post where someone did the superglue trick - I have 2 watches I can't open (one that looks similar to your second and the other a Seiko) and was planning on giving this a go

[Zero]

Superglue trick works great, but does it work on chrome coated casebacks? I think its only good for stainless steel. It doesn't say stainless steel in the pics.

[Marc]

1 hour ago, Zero said:

It doesn't say stainless steel in the pics.

From what I can see both of those watches are cased in stainless steel all round, you'll probably find the inside of the case back stamped as such when you eventually get in there. Even if the bezel and mid case should prove to be a chrome plated base metal, the back is still almost certainly going to be stainless.

That being said I don't see that there would be any reason why the super glue nut trick shouldn't work on a chrome plated surface.

[ColinC]

Success! 2 watches opened without a scratches!

[RichardHarris123]

Just an idea.  For snap backs, adjust a case holder so the back is free but it holds the lugs.  Glue a nut to the back, drill a hole in a metal bar, just large than the  thread of the nut.  Put another nut a bolt , pass through metal bar and screw the bolt into the nut on the back of the watch.  Tighten the other nut, a bit like a pinion puller. I'll make a prototype and post a picture. 

Here's my idea, the adjustment screw in the holder may get in the way, so could be substituted for a hole in a piece of wood. Can you tell I took art at school?  Hehe 

[Geotex]

Pulling a disk from the center tends to contract the perimeter, so although you could get a good mechanical advantage with such a setup, I think it might make the mating edges of the case and back bind that much tighter...

People have described pulling a crystal out from the center like this, in which case the shrinking of the perimeter would be helpful. 

[RichardHarris123]

13 minutes ago, Geotex said:

Pulling a disk from the center tends to contract the perimeter

Good point. 

[Waggy]

Sorry, late to the party - I've tried the nut trick a few times and not had any success, obviously I'm doing something wrong.... cheap/old glue? Just wanted to add a trick that was not mentioned that sometimes helps with a screw back. I apply anti-sieze oil (looks feels and smells like WD40 ) and let it sit for a few hours then I double bag the entire watch and place it in a mug with hot water (reasonably hot, not boiling). The sealed bags ensure the watch is not flooded, but allow the heat from the water to expand the metal of the watch case and case back. Then I quickly remove from the water and apply an ice cube to the case back, this should result in the case enlarging (due to the hot water) and the case back shrinking due to the cold of the ice cube, sometimes this minute change in size can loosen or break up any debris binding the threads and/or provide enough room for the threads to move and allow you to open it up.

Whilst here I do have another related issue, I have a jump hour watch which I acquired about 2 years ago, which has a screw type case back which I can't get into. The problem is that the case back just spins and spins, so the internal thread is obviously damaged to the point where the thread is now a circle instead of a spiral (if that makes sense?). Other than brute force and treating it like a snap type case back and probably damaging the case and/or case back I'm at a but of a loss. I checked with the previous owner who confirms it is a screw type and the eBay pictures show a thread, but it arrived to me screwed down and with the issue outlined above. Any ideas?

10 hours ago, RichardHarris123 said:

Good point. 

Almost like you need a push in the center and pull on the rim as you pull the entire thing:

 

Just wondering if there is some kind of cam or spring system that would automatically push on the center as you pull the entire thing a bit like a presto tool in reverse?

PS

To clarify, I mean the same kind of mechanism as a presto tool, not an actual modified presto tool which would be way too flimsy.

Edited December 7, 2023 by Waggy

[Neverenoughwatches]

19 hours ago, ColinC said:

I watched a YouTube post where someone did the superglue trick - I have 2 watches I can't open (one that looks similar to your second and the other a Seiko) and was planning on giving this a go

Tried it many times and it has always worked. The nut needs to be clamped in order to get full adhesion. Obvious precautions to protect to crystal and front of the case.  This is where another great use of the screw crystal press comes in. Afterwards fill the nut wuth acetone and leave for a couple of hours, you might need a sharp blade to get under it.

[Waggy]

This one should get it!

 

[Neverenoughwatches]

19 hours ago, Zero said:

 

 

16 hours ago, RichardHarris123 said:

Good point. 

Pulling on the center of the caseback   will reduce its perimeter helping to release its tension. Same as pressing a snap back on has the opposite effect, one reason why some snap ons are tough to get back on by hand. Always push on around the edge, never the center. So in theory your idea should work, i think the problem is keeping the watch held in the case holder. I think it pull straight out, ideally the set up needs to pushing onto the watch case but then you have the risk of breaking something like the lugs.

6 hours ago, Waggy said:

Whilst here I do have another related issue, I have a jump hour watch which I acquired about 2 years ago, which has a screw type case back which I can't get into. The problem is that the case back just spins and spins, so the internal thread is obviously damaged to the point where the thread is now a circle instead of a spiral (if that makes sense?). Other than brute force and treating it like a snap type case back and probably damaging the case and/or case back I'm at a but of a loss. I checked with the previous owner who confirms it is a screw type and the eBay pictures show a thread, but it arrived to me screwed down and with the issue outlined above. Any ideas?

I had the same issue with a divers watch six months ago. The threads had been crossed, it was a combination of turning the glued on nut with some leverage from a blade that removed it. I haven't gotten around to working on it yet so putting in back on is going to be another problem. 

Edited December 7, 2023 by Neverenoughwatches

[Marc]

17 minutes ago, Neverenoughwatches said:

Pulling on the center of the caseback   will reduce its perimeter helping to release its tension

Pulling on the center of the case back will cause it to dome outwards, reducing its diameter and causing it to grip the case even harder, as pointed out by @Geotex above.

[Neverenoughwatches]

43 minutes ago, Marc said:

Pulling on the center of the case back will cause it to dome outwards, reducing its diameter and causing it to grip the case even harder, as pointed out by @Geotex above.

i dont get that, i can see how pushing the center would splay the rim edge outwards. 

43 minutes ago, Marc said:

Pulling on the center of the case back will cause it to dome outwards, reducing its diameter and causing it to grip the case even harder, as pointed out by @Geotex above.

Reducing the caseback diameter will grip the case harder ? 

43 minutes ago, Marc said:

Pulling on the center of the case back will cause it to dome outwards, reducing its diameter and causing it to grip the case even harder, as pointed out by @Geotex above.

Haha yes i do get it senior moment, too busy thinking about the missus fashion watch that i did 2 days ago, the retaining lip was on the caseback not the case. I'll go back to sleep now

Edited December 7, 2023 by Neverenoughwatches

[ColinC]

I chose to superglue a rather large bolt (rather than a nut) to the case back when I did this in order to get more surface area.  I also filed and polished the head of the bolt which originally had some raised lettering on the top.

With a large enough bolt you should limit the amount of caseback bending if you were to use this for pulling snap on backs