Relativity of units - the Omega way

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MKTheVintageBloke
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Relativity of units - the Omega way

Post by MKTheVintageBloke » June 16th 2020, 12:07pm

As you know, recently I've got me a ca.1960 Seamaster ref. CK 14730. Sadly, it's not safe for wear for now.

The problem is...the crystal. The watch is fitted with an ordinary - and not well-fitting - hesalite, which means that any impact by the edge can dislodge it, and send it flying to the floor.

Seamasters, be it in normal or unishell cases, used an armoured hesalite crystal, i.e. one equipped with a metal tension ring. OK, that's not a problem, there are generic crystals of that kind, and they're not even uncommon.

So, I looked up the correct Omega part for the 14730, which is the PX5072. It's a size 316, which means 31.6mm. So, I've started looking for a size 316 armoured hesalite. Because, good luck finding the PX5072 Omega part. Here, it's another hearty "fuck you" to the Swatch Group from me.

What the fuck? Almost all were bought out. Finally, found one. Picked it up today. Went to have the crystal installed.

And...fuck. While it was being pressed in, the crystal just cracked.

The reason?

The reason is that while the specs for the crystal for this reference provide it as a 316, the case actually takes a size 315. Which means that, well, fuck, looks like Omega even developed their own version of the metric system. Because, like, they couldn't just fucking stick to the normal metric system like they fucking should.

So, Omega measurements seem to not be equivalent to the measurements as per any caliper.

If any of you would ever want to change the crystal in a 1960s Omega, DON'T TRUST THE MOTHERFUCKING SPECS. Get that thing measured.

I'll order a size 315, and here's hoping that it won't fucking snap while being installed.
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Re: Relativity of units - the Omega way

Post by koimaster » June 16th 2020, 12:48pm

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Re: Relativity of units - the Omega way

Post by MKTheVintageBloke » June 16th 2020, 1:24pm

Technically, the absolutely correct part would be the PZ5072L(D), i.e. silver-tone tension ring and date magnifier. I have just ordered the generic (AF Switzerland) size 315 armoured crystal (ref.4006-315), and I'll see where that'll take me. The factory-original steel rehaut is still in the watch, so as long as it won't pose a problem with the new generic crystal, I won't need to buy the PZ5072.

The problem of the measurements being relative remains. Contacted a friend, and it turns out that generic crystals in Seamasters do tend to snap during installation, if indeed the size was chosen based on the specs of the original part. Happens more than often. So, the issue of Omega's 31.6mm not really being 31.6mm (and being - most likely - a caliper-measured 31.5 instead) stands. And so stands my warning against ordering based on specs alone, rather than the caliper.
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Re: Relativity of units - the Omega way

Post by gerdson » June 16th 2020, 1:36pm

Shit. But I also recently read on uhrforum.de, that Tissot PR 516 GL crystals, which we all believed were completely unavailable in years now, actually can be easily replaced by taking some other dimension, just 0,1mm larger and (maybe) simply dragging it across a piece of sand paper.
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