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Replacing Existing Crystal With Sapphire

dferrier

By dferrier
in Watch Repairs Help & Advice

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dferrier New Member

dferrier

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I just purchased a used Citizen watch and would like to replace the crystal. It is a Black Eagle Skyhawk (if that really means anything... :) ) and the case number is C652-S030480.

 

I contacted Esslingers and they tell me there is no sapphire crystal available for that watch. But aren't most round crystals more or less standard shapes and profiles?

 

If I measured the old crystal couldn't I order a sapphire one that would fit?

 

 

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bobm12 Distinguished Member

bobm12

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Hi dferrier, welcome to the forum! Your assumption on measuring and ordering is rather correct, only, it is not -- believe it or not -- as exact as you would think. When ordering generic crystals the rule of thumb is to order one size up and one size down in addition to the original measurements. The tiny difference can make a huge difference! :)

 

Saphire is expensive!

 

Cheers,

 

Bob

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dferrier New Member

dferrier

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Hi dferrier, welcome to the forum! Your assumption on measuring and ordering is rather correct, only, it is not -- believe it or not -- as exact as you would think. When ordering generic crystals the rule of thumb is to order one size up and one size down in addition to the original measurements. The tiny difference can make a huge difference! :)

 

Saphire is expensive!

 

Cheers,

 

Bob

 

Thanks Bob,

 

What I am thinking and correct me if I am wrong about this. I have never actually taken a watch apart (yet) and so I don't know if all watch crystals are custom fitted by model or if they are more generic.

 

My thought was that if they mostly come in standard sizes and shapes I could order the correct size and shape in saphire.

 

Or is that a vain hope?

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jdm Distinguished Member

jdm

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I just purchased a used Citizen watch and would like to replace the crystal. It is a Black Eagle Skyhawk (if that really means anything... :) ) and the case number is C652-S030480.

 

I contacted Esslingers and they tell me there is no sapphire crystal available for that watch. But aren't most round crystals more or less standard shapes and profiles?

 

If I measured the old crystal couldn't I order a sapphire one that would fit?

 

 

I've looked at this watch and it seems to have a flat crystal which is easy to find in all measures. However since you never worked with watches if this is an one time desire I'd recommend that you bring it to a local watchmaker to have it measured and replaced.

Edited by jdm
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Marc Distinguished Member

Marc

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dferrier,

 

Bob's advice re; ordering sizes 1 up and 1 down is particularly pertinent when replacing acrylic or cellulose crystals as they are not dimensionally stable over time and they usually shrink, so measuring the one you take out may not give you an appropriate size for the replacement.

 

I'm not so sure that it is quite so applicable to glass or sapphire though (no offence Bob) as these materials are much more dimensionally stable over time, so if you are taking out a glass or sapphire crystal, and assuming that it was a good fit when you take it out, it should provide an accurate size for ordering the replacement. Also glass and sapphire are ground to precise dimensions so what you get should be exactly the size you ordered. Check the thickness as well as the diameter though.

 

The only time I order a range of sizes for replacement glass is when the original is broken or missing and I have to measure the aperture in the case which is not so precise as it takes no account of the gasket. Otherwise I just order one the same size as what I take out and I've had no problems yet.

 

With acrylic though the manufacturing process can be a little less consistent and if you combine the manufacturing errors with age shrinkage and measuring inaccuracies (it's very easy to slightly deform the crystal whilst measuring with a calliper) you can see where it becomes necessary to hedge your bets. 

 

Obviously over time you build up a stock of unused crystals of varying sizes making it easier to change acrylic crystals in the future.

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bobm12 Distinguished Member

bobm12

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Hi Marc,

 

None taken!

 

I just sometimes do this one up and one down when considering the plastic gasket that holds the crystals regardless of the material they are made of. My reasoning -- and findings -- is that sometimes those generic rings/gaskets come with different thicknesses/dimensions to the ones originally in the watch and the replacement won't fit well...also if still using the old gasket (not recommended in an ideal world), it may be deformed -- if still flexible and usable -- and the new crystal won't be able to compress it adequately creating a future door for water to crawl in. Also there is always the error inherent to the measuring device and the user: mainly me.

 

I've had all that happen a few times so now I err on the "too much" rather than the "too little" and as you say, the collection of crystals grow more and more... :)

 

Of course, another story is when the crystal is glued to the case or maybe when the watch is "brand new" and needs -- or the owner wants -- a new higher end crystal.

 

Cheers,

 

Bob

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