Screw down case backs.

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MiniMpi
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Screw down case backs.

Post by MiniMpi »

I finally took the plunge to try opening some screw down case backs.

I have ventured into changing some batteries of late which were held down by screws and I'm happy enough doing these now.

My C70 Ascari COSC needs a battery so I wanted some practice before tackling this beauty.

I purchased a tool kit from Amazon recently to assist with bracelet link removal and it's excellent.

The case back opener is a three prong affair with three different types of attachments to deal with different hole types on the various case backs.

My brother Sean's Rotary Chronospeed is in need of a new battery so I tackled this one first. This had gotten a battery before so I figured it would be easier and it was very straightforward. I also have the case holder which is vital for assisting you in the job.

The next two I tackled were my work colleague's C60 300 quartz 43mm and his C6 Kingfisher (my old one).

The C6 again had had a few battery changes so was also straightforward.

The C60 300 however had never had a replacement battery.....
This was indeed quite difficult to open and the case opener did slip on occasion but I finally got it open after so perseverance.

All three watches are far from watch box queens and have various marks and scratches and considerable amount of gunge......!!
So they were good ones to test how to do this job.

Ordered the various batteries needed, Renata ones of course.
I left the case backs loose until I can change the batteries when they arrive.

Photos below, Rotary first followed by the C6 then the C60 300 and the tool kit I bought.

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H0rati0
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Re: Screw down case backs.

Post by H0rati0 »

Ferg

I loath the Jaxa type case tools. In my (admittedly limited) experience the three prong ones are difficult to locate and keep tightly in position on the caseback slots. The two prong types are better and you can exert more pressure, if necessary with a wrench. Better yet are the professional models on stands which incorporate a case holder but those are a relatively serious investment, though if you plan on doing this regularly, that's the way to go.

Have fun

nik
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Re: Screw down case backs.

Post by MiniMpi »

H0rati0 wrote: Sun May 02, 2021 10:58 pm The two prong types are better and you can exert more pressure
I've heard this from someone else as well this evening.
I'll look into getting one of the two prong type opener.

Cheers Nik.
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Re: Screw down case backs.

Post by JAFO »

H0rati0 wrote: Sun May 02, 2021 10:58 pm Ferg

I loath the Jaxa type case tools. In my (admittedly limited) experience the three prong ones are difficult to locate and keep tightly in position on the caseback slots. The two prong types are better and you can exert more pressure, if necessary with a wrench. Better yet are the professional models on stands which incorporate a case holder but those are a relatively serious investment, though if you plan on doing this regularly, that's the way to go.

Have fun

nik
Funny you mention that. I have been struggling to move some case backs with a Jaxa. I saw some stand devices for around £80 at the cheapest but it's a lot to spend and still not get a solution. Can you recommend one?
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Re: Screw down case backs.

Post by gaf1958 »

I’ve used a cheap three pronged style for the last couple of decades on, I guess, over a hundred or more watches and have had very few problems with it. On a really tight case back you may need to be more careful, but I have sometimes wondered if I should have a two pronged model - just in case.

I do have an aftermarket Omega Seamaster case opener (five prongs, fixed in place - it has worked superbly the few times I’ve used it), but some other case back styles (e.g. Rolex/Tudor) I haven’t had to worry about. Well, case backs with screws are obviously ok, even if they are easy to lose....

The new Omega Niaid case back looks a challenge (and is probably designed to be) but 12 or 8 sided case backs (e.g. Panerai, Baume et Mercier) are going to be a problem for me, as I have a number of vintage Tissots that use that style of case back. I’ve used a very fine (i.e. thin and high quality, no wobbly jaws) shifting spanner on the Tissots with good success, but it’s not the right tool; it may be time to invest in a sticky rubber ball.
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Re: Screw down case backs.

Post by Bident »

H0rati0 wrote: Sun May 02, 2021 10:58 pm Ferg

I loath the Jaxa type case tools. In my (admittedly limited) experience the three prong ones are difficult to locate and keep tightly in position on the caseback slots. The two prong types are better and you can exert more pressure, if necessary with a wrench. Better yet are the professional models on stands which incorporate a case holder but those are a relatively serious investment, though if you plan on doing this regularly, that's the way to go.

Have fun

nik
^^^+1 from me, Nik. I had no success with the Jaxa tool, but using a simple two prong tool I opened two very difficult case backs. Following tips I learned, I used electrical tape to cover the case back, especially the two point of contact, and then also put a plastic ziploc bag (cut up to fit the case) over it as well.

Forgive me as I've mentioned this before, but over 80% of the casebacks I have opened I used a friction ball. I would highly recommend trying one first as they are very simple to use and have zero risk of scratching the watch.

Well done on your part, Ferg!
Best regards,
John
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Re: Screw down case backs.

Post by MiniMpi »

Thanks John, ordered a friction ball this evening.
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Re: Screw down case backs.

Post by Lavaine »

Congrats on a job (partly) well done. I commented on the FB post, but I'll leave the same comment here: Invest in a toothbrush or other small soft brush, and clean around the case backs with a damp brush prior to opening them. In your pictures you can see a lot of gunk collected around the back of the C6. If that gets into the watch it can foul the movement, or cause problems with the seal of the case back if any of it interferes with the gasket fitting.

Also, be REALLY careful removing the battery retainer screw on the C6 and C60. That spring is under a surprising amount of tension, and can send that screw flying far enough that you'll never find it. Go ahead, ask me how i know.
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Re: Screw down case backs.

Post by hgercek »

Don't forget applying silicone grease on the gasket before closing the case back. I just opened my C65 Sandhurst case for fine regulation. It was easy to open and close it but I wonder if it is still perfectly water resistant.
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Re: Screw down case backs.

Post by H0rati0 »

JAFO wrote: Sun May 02, 2021 11:26 pm
I saw some stand devices for around £80 at the cheapest but it's a lot to spend and still not get a solution. Can you recommend one?
I cannot directly, for me so far a friction ball or a two pronged have done the job. I had thought about about one of these, but don't really do enough to justify ATM. https://www.cousinsuk.com/product/unive ... wiss-style
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Re: Screw down case backs.

Post by H0rati0 »

Some good accumulated experience here!

Top Tip: Friction ball is always worth trying first - after careful cleaning of the case back, natch.
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Re: Screw down case backs.

Post by H0rati0 »

hgercek wrote: Mon May 03, 2021 8:42 am Don't forget applying silicone grease on the gasket before closing the case back.
Defo +1!

after making sure everything is spotlessly clean, mostly best done before opening in the first place.
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Re: Screw down case backs.

Post by timor54 »

hgercek wrote: Mon May 03, 2021 8:42 am Don't forget applying silicone grease on the gasket before closing the case back. I just opened my C65 Sandhurst case for fine regulation. It was easy to open and close it but I wonder if it is still perfectly water resistant.
To be a little pedantic, applying silicon grease on the caseback gasket is not done primarily for water tightness. Its main purpose is to prevent the gasket from sticking to the case/caseback and rumpling up as the caseback is tightened, which would then impair water tightness. As long as it’s tightened down smoothly then it should be fine.
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Re: Screw down case backs.

Post by hgercek »

timor54 wrote: Mon May 03, 2021 10:24 am
hgercek wrote: Mon May 03, 2021 8:42 am Don't forget applying silicone grease on the gasket before closing the case back. I just opened my C65 Sandhurst case for fine regulation. It was easy to open and close it but I wonder if it is still perfectly water resistant.
To be a little pedantic, applying silicon grease on the caseback gasket is not done primarily for water tightness. Its main purpose is to prevent the gasket from sticking to the case/caseback and rumpling up as the caseback is tightened, which would then impair water tightness. As long as it’s tightened down smoothly then it should be fine.
Yes I know. I meant it is hard to know if the gasket is in the right place after closing the case back. But I hope as long as you can close it smoothly everything is fine.
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Re: Screw down case backs.

Post by kiter65 »

Good work Ferg :thumbup:
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