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Discussion Starter #1 (Edited)
Hi guys,

How many of you need this rare 7A28 7A38 glass.
Part number 310W64GN00
7A28-7040/9
7A38-7070/80
The glass has a large polished chamfer.


Cheers

Bry

 

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Would be nice to have this available, but I don't have any watches that need it right now... Both my 7A28 and my 7A38 have scratch-free crystals ATM ;) :grin:
 

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I'm going to take a couple. They will sell on ebay as nobody has these with the correct champher.

The 2mm is slightly thicker than the original and the clearance between the champher and the bezel is fairly tight on the original . So long as the champher starts at the same height as the original and is at the same angle it will be good.
 

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Hi Bry, I've just checked a NOS one that I have. Both bevels are polished.

I'll take some pictures tomorrow in natural light and post here.
 

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Discussion Starter #12
Hi Simon,

PaulS said lower bevel is ground, the glass from Dan has side and lower bevel ground.
 

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My bad. I though the purpose of the thread was to confirm how the original looks like. Did not know it was “is this good enough” instead.


Sent from my iPhone using Tapatalk
 

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Here's a few pics to help










both are NOS.

The fact that the lower edge is polished bevel just aids pressing it in, especially with a new crystal gasket. Once in as Bry says its hidden.

Bry - a crystal that is also needed is the 315W16GN00
 

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PaulS said lower bevel is ground, the glass from Dan has side and lower bevel ground.
My bad. Obviously my eyesight (or memory) are failing me. :redface:

It's academic anyway, because the lead-in (lower) bevel is hidden by the gasket when fitted and I doubt has any effect on refraction.

Personally I'd rather see such a repro' crystal without any lower 'lead in' bevel. Just the polished upper bevel. As I wrote in a thread on my forum (actually started by Simon), many years ago, I tend to re-use crystal gaskets - unless they're damaged. Omitting the 'lead in' bevel may require more physical effort to press the crystal fully home, but it gives you a 'second bite' at the gasket.

If you examine an original Seiko crystal – either the old one you have pressed out (or if you’re fortunate to have a NOS genuine Seiko replacement), apart from possibly having a polished decorative top bevelled edge, you will notice that it also has another ‘lead in’ bevelled edge ground on the underside. It is this ‘lead in’ edge which facilitated fitting the crystal, in the factory when the watches were made. It is this ‘lead in’ bevel which leaves the tell-tale ‘step’ indentation in the original gasket, where it doesn’t compress the gasket for its entire depth. As you know, I am an advocate for fitting Sternkreuz toughened glass replacement crystals, particularly their MSM range. I can’t say that they are any harder (in terms of scratch resistance) than Seiko Hardlex, but they certainly are stronger, particularly if you give them ‘a bit of welly’ pressing them back in. I have never once broken a Sternkreuz crystal pressing it back in, but I have shattered the odd Seiko Hardlex (pressing them out), and cracked a few Cousins ‘cheapies’ pressing them in, in my early days.

The other thing I like about using Sternkreuz MSM crystals, is that they usually have NO ‘lead in’ chamfered edge. The edges of the crystal are ground straight and parallel. That may make them harder to 'seat squarely' initially - and to press in, but it also gives you a ‘second bite’ at the lower part of the original Seiko crystal gasket.

If you look at the Sternkreuz catalogue (Page 6), there are a couple of 'specials' in their XMF range, which don't have 'lead in' beveled edges.
Their p/n XMF310.848 would almost be perfect for this application (dimension wise), except the polished bevel is way too big. :rolleyes:
 
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