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Problem With Snapping A Snap-On Case Back On

WillFly

By WillFly
in Watch Repairs Help & Advice

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WillFly Distinguished Member

WillFly

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The 4 free watches I got this morning are little crackers - far better than I expected them to be, with simple but well-made movements and fairly rugged cases. All keeping good time so far and with clean movements. The Chinese Chumei and the Indian HMT Suraf have screw-on cases and were simple for me to uncover, photograph and re-cover. The other two Indian HMTs have parashock cases with snap-on backs. Both were stiff to prise off. One - the Kohinoor - went back OK with the case press, but the other snap-on back will just NOT go on, even with the case press screwed very tightly. I've checked it for position, notches, etc., and can't see a problem. But will it click in? No it won't.

 

Any advice?

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atimegoneby Super WRT Addict

atimegoneby

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 but the other snap-on back will just NOT go on, even with the case press screwed very tightly. I've checked it for position, notches, etc., and can't see a problem. But will it click in? No it won't.

 

Any advice?

Hi Will,

 

I have the same problem at the moment (posted in Armani chronograph) and I actually broke the glass trying !, I think it might be because my press has nylon dies the nylon is flexing and absorbing some of the pressure whereas aluminium dies would not do this, I'm going to try another press or as Geo says

 

''A big hammer'' :pulling-hair-out:

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bobm12 Distinguished Member

bobm12

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I use nylon dies and as I said before, the dice have to be selected properly so the pressures apply only on the spots needed, otherwise the crystal breakes or the back shifts and may damage the stem or any other part. It is possible that being nylon they are much more picky than the alluminum ones.

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clockboy Distinguished Member

clockboy

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Will,

I have had a few of these bugg**rs I think the back distorts when opened. I found that a smear of silicon grease on its rim and a machine press does the trick. I was told once by a watch repairer that putting the back in a freezer for a while helps as it very slightly shrinks the metal. I have never tried this method but the theory sounds good.

Edited by clockboy
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Mark Distinguished Member

Mark

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Thanks for the grease heads-up, folks - I'll give it a go!

 

Im sure I need not say this but make sure your lower die clears the glass.

 

Is your press a lever type or a screw type? I find the screw type to be far more useful for these annoying tight ones as I feel more in control. But keep making adjustments to the position and you should get to the sweet spot.

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WillFly Distinguished Member

WillFly

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Cheers Mark - yes, I've been very careful to avoid pressing the glass, and made several adjustments to the upper die position.

 

This morning, I even inserted a 50p piece between the screw of the press and the top of the upper die - because the pressure was pushing the screw into the plastic upper die rather than exerting its full pressure on the case back. Result? The screw just bored into the 50p piece!

 

So, no more on this until I get the Seiko silicon grease.

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bobm12 Distinguished Member

bobm12

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Alternatively, heating the whole watch under a torch and leaving the back at room temperature will avoid humidity! :)

 

On a more serious note, I started to think: Maybe the gasket is being pinched while pressing the back on. Did you check the gasket Will? It may be hard to spot in some watches thou.

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WillFly Distinguished Member

WillFly

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if you post it to me I'll put it on for you, although with the cost of postage its less than an ideal way!

That's a very kind offer, Lee, and I may well take it up. I'm seeing a watch repair friend of mine next Tuesday down near Southampton - one of my regular visits where we drink coffee and talk watches for a morning - and I have various little projects for him. I believe he has some silicon grease so I'll take it over with me and we'll see what he can do as he also has various case presses. If he can't succeed, I'll gladly contact you.

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WillFly Distinguished Member

WillFly

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Success with the case back this morning. I went over to see my watch repair buddy in Bursledon and - between us - we managed to get one side of the case back firmly in, with one side still proud. I spotted a small bench vice with 4" jaws attached to the side of his workbench and suggested that, with suitable, padding, that might do the trick.

 

So we put the right plastic dies in place, added some extra dies for safety and, working our way around the rim, used the vice to ease case and back closer together. Finally - with a gunshot sound - the case snapped together! It's never coming off again while I have it!

 

And all the while the watch was ticking away merrily... :woohoo-jumping-smiley-emoticon:

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