What part number has my SEIKO crystal?

[VWatchie]

I’m servicing my first SEIKO watch housing a calibre 7S36B. Got it on eBay for about £70 and it seems to be in reasonably good condition. The crystal is somewhat scratched. I don’t know if it is mineral or sapphire glass. If mineral (which I assume) I suppose I could diamond paste the scratches, but for several reasons I would like to replace the crystal, the most important reason being I’d like to learn how to. I’ve already removed the old crystal and it’s intact so I could measure it.

However, CousinsUK.com has a ”Seiko Glasses List (Under Construction)” with hundreds and hundreds of mostly original SEIKO crystals. Each crystal is listed with SEIKO’s part number, for example “Glass, Seiko 095N02GN00”. The question is, how do I obtain the part number of my SEIKO crystal?

The numbers I’ve found on my SEIKO are:
7S36-05C0 – printed on the see-through case back,
0D0349 – engraved on the rim of the case back, and
7S36B – engraved on the oscillating weight.

[watchweasol]

Hi VWatchie  I have attached the SEIKO casing guide in the hope you find it useful in your search.

03. Casing Guide seiko.pdf

[watchweasol]

Hi Watchie  found some more information you may find use full       cheers

Deciphering Seiko Case Back Information — Plus9Time.html Servicing_Guide.pdf

[JohnD]

According to Boley the crystal you need is 310PB3JN02...

 

Edited June 4, 2020 by JohnD

[VWatchie]

Wow, thanks a ton! 

[jdm]

8 hours ago, JohnD said:

According to Boley the crystal you need is 310PB3JN02...

As mentioned in similar threads, the fact that boley.de list a part does not mean that it's available. You need to login to see its stock status, in this case it's yellow light which means they don't have it, and good luck opening an account first with them and they ordering it.

Also, and this is another frequently asked question, there is no need of hunting original Seiko 5 crystals, as they are invariably flat ones of mineral glass. Just measure thickness (likely it's 1.15mm), we know already from the P/N that dia. is 31.0mm, and order a generic, that will be cheaper and identical anyway.

Edited June 5, 2020 by jdm

[JohnD]

6 minutes ago, jdm said:

As mentioned in similar threads, the fact that boley.de list a part does not mean that it's available. You need to login to see its stock status, in this case it's yellow light which means they don't have it, and good luck opening an account first with them and they ordering it.

Also, and this is another frequently asked question, there is no need of hunting original Seiko 5 crystals, as they are invariably flat ones of mineral glass. Just measure thickness (likely it's 1.15mm), we know already from the P/N that dia. is 31.0mm, and order a generic, that will be cheaper and identical anyway.

I wasn't suggesting getting one from Boley,  just indicating the correct part number and qualifying the information with the source detail.............At least the OP now has a starting point with a part number to search for .

It is actually available HERE (no Boley content)..........

[jdm]

2 minutes ago, JohnD said:

It is actually available HERE (no Boley content)..........

£14.99 + 5.50 EU Shipping for something that cost less than one pound 
 

[JohnD]

26 minutes ago, jdm said:

£14.99 + 5.50 EU Shipping for something that cost less than one pound 
 

Seems about a normal price for a Seiko crystal these days, to me, rarer crystals go for MUCH more....if you can get them for less than £1 please share the information.....

(while the one listed may be a generic crystal at least, as you can get the new gasket to go with it, you know that it will fit the watch it is specified for....)

Edited June 5, 2020 by JohnD

[jdm]

3 minutes ago, JohnD said:

Seems about a normal price for a Seiko crystal these days, to me, rarer crystals go for MUCH more....if you can get them for less than £1 please share the information.....

As mentioned above £1 will be for a generic one that is identical and indistinguishable

https://www.cousinsuk.com/product/130mm-cousins

And fortunately crystals can also be polished to perfection.

Then if one wants to treat a Seiko 5 worth perhaps 60 pounds with money parts costing a third of that, their choice 

 

[JohnD]

1 minute ago, jdm said:

As mentioned above £1 will be for a generic one that is identical and indistinguishable

https://www.cousinsuk.com/product/130mm-cousins

And fortunately crystals can also be polished to perfection.

Then if one wants to treat a Seiko 5 worth perhaps 60 pounds with money parts costing a third of that, their choice 

 

The Cousins crystals shown are almost certainly the wrong thickness and do NOT have the bevel on the top edge, also the price shown is pre VAT and shipping, in this case not a route I would take.

I do have a Cousins account and have used their generic crystals but have  another source for thicker bevelled crystals but wasn't going to recommend those as I couldn't be sure if the diameter was exactly correct to suite the original Seiko gasket, as while the Seiko part numbers indicate a diameter that is not always the exact size, sometimes varying by  a few thousandths of an inch......At least with the eBay one a suitable crystal gasket can be sourced at the same time...

[jdm]

2 hours ago, JohnD said:

The Cousins crystals shown are almost certainly the wrong thickness and do NOT have the bevel on the top edge

That can be know once the original is measured. All the Seiko 5 I've handled.have no bevel, they sit flush to the bezel. It can be that a generic one was to be so slightly proud. 

Quote

I couldn't be sure if the diameter was exactly correct to suite the original Seiko gasket, as while the Seiko part numbers indicate a diameter that is not always the exact size, sometimes varying by  a few thousandths of an inch.....

I don't know about Inches and their thousands but Seiko and generic crystal are measured in metric units, and available with intervals of 0.10mm. Thea many I have replaced all did fit perfectly in case of doubt they low cost allows to order the next sizes. 

[JohnD]

3 minutes ago, jdm said:

That can be know once the original is measured. All the Seiko 5 I've handled.have no bevel, they sit flush to the bezel. It can be that a generic one was to be so slightly proud. 

I don't know about Inches and their thousands but Seiko and generic crystal are measured in metric units, and available with intervals of 0.10mm. Thea many I have replaced all did fit perfectly in case of doubt they low cost allows to order the next sizes. 

The generic crystals sold by Cousins are indeed in steps (usually but not always) of 0.1 of a mm, this equates to 0.003875", (or just under 4 thou to the uninitiated), I find 0.1mm just a tad 'coarse' when measuring so think in thous and 1/10th thous when trying to be precise....Seiko do tend to round up or down when specifying diameters in their crystal part numbers and I rarely find that they come in convenient sizes like 30.0, 31.0 etc etc. I learnt the hard way and have a few 'nearly right diameter' generic crystals in stock....which when you take into account the carriage cost, if you are not making a bigger order with Cousins, starts to show that it is not always economical to take the 'cheap route'....

[VWatchie]

I haven’t yet made up my mind whether to go original or generic, but if I can replace the crystal and gasket with generic parts there’s a substantial amount of money to be saved and considering I paid approx. £70 for this watch, adding another £25 (glass + gasket + shipping) feels really steep.

However, there’s another problem; as you can see in the pictures, my glass gasket is black, and all glass gaskets I’ve seen so far are white(ish). Not sure how big of a problem this would be for the aesthetics of the watch, but it would be nice with a black gasket, but Cousins don’t seem to provide them?

Also, when I pressed out the crystal, the gasket stayed in the case as well as the chapter ring and the gasket seems to sit really hard which makes me wonder if it is glued or if it is simply years of dirt that makes it stick. Do you have any advice on how to tackle it (and the chapter ring)?

If you think my questions seem “funny”, I should mention that I’m completely new to SEIKOs, mineral crystals, and glass gaskets. Previously I’ve only handled plastic and armored glasses. So, please bear with me!
 

[jdm]

24 minutes ago, VWatchie said:

If I can replace the crystal and gasket with generic parts

There is no need to replace the gasket unless it has been badly damaged pulling it out without care. 

Quote

Also, when I pressed out the crystal, the gasket stayed in the case as well as the chapter ring and the gasket seems to sit really hard which makes me wonder if it is glued or if it is simply years of dirt that makes it stick

There is no glue nor dirt, a nylon gasket provides impermeability by mean af a slight friction fit, that is easily handled with proper crystal press and crown type dies. 

Edited June 5, 2020 by jdm

[JohnD]

1 hour ago, VWatchie said:

I haven’t yet made up my mind whether to go original or generic, but if I can replace the crystal and gasket with generic parts there’s a substantial amount of money to be saved and considering I paid approx. £70 for this watch, adding another £25 (glass + gasket + shipping) feels really steep.

 

Also, when I pressed out the crystal, the gasket stayed in the case as well as the chapter ring and the gasket seems to sit really hard which makes me wonder if it is glued or if it is simply years of dirt that makes it stick. Do you have any advice on how to tackle it (and the chapter ring)?

Well the only 'original' crystal I can find listed anywhere is in Russia and at 1,800 Rubles plus carriage is a lot more expensive. If you do decide to go generic make sure that the diameter and thickness of the replacement crystal is IDENTICAL  to the one that you have removed and that it has the same edge chamfer profile and you will be able to fit it back in the original black nylon gasket, with care.

I recently managed it with this Seiko 7546-8270 with a similar black nylon gasket to your watch... In that case I was able to use a Sternkreuz XMF 300.863 equivalent, which measures 29.98mm diameter x 2.00mm thick with a 45degree x 1mm chamfer on one side. If there is a 310 version of this crystal, if the thickness and profile is the same as your crystal then at less than £4 from Cousins, it is a strong contender....

edit:- Cousins list 4 Sternkreuz XMF310 crystals, the 310W21GN equivalent, XMF310.857 would appear to have this profile....

 While the XMF310.848 appears to be thicker and has a more pronounced edge profile more like the one I fitted to my 7546 above...

 

 

Edited June 5, 2020 by JohnD

[VWatchie]

3 hours ago, jdm said:

There is no glue nor dirt, a nylon gasket provides impermeability by mean af a slight friction fit

Well, that's good to know. Thanks!

 

3 hours ago, jdm said:

that is easily handled with proper crystal press and crown type dies.

I have a good crystal press but I need to research what "crown type dies" are. Do I understand you correctly that I would use a crystal press and crown type dies to remove the gasket and the chapter ring? If so, I can't picture how I would go about it. I really want to get the chapter ring (and the gasket) out so that I clean and polish the case without risking damaging the lume (which is still in good condition) on the chapter ring.

[VWatchie]

@JohnD Thanks for your research and your detailed info. Very much appreciated! 

[JohnD]

3 minutes ago, VWatchie said:

Well, that's good to know. Thanks!

 

I have a good crystal press but I need to research what "crown type dies" are. Do I understand you correctly that I would use a crystal press and crown type dies to remove the gasket and the chapter ring? If so, I can't picture how I would go about it. I really want to get the chapter ring (and the gasket) out so that I clean and polish the case without risking damaging the lume (which is still in good condition) on the chapter ring.

Be VERY careful if you remove the crystal gasket, the nylon ones are very brittle and can break! I would be more inclined to refit the old crystal then polish the case with it, and the chapter ring, in place.

I just looked through my stock of crystals and for some totally unknown reason I appear to have four of the XMF310.848 ones  in stock! (haven't a clue how that happened)

 I can now confirm the dimensions as  being 30.98mm diameter and 1.9mm thick, with a heavy chamfer on one edge, approx 45 degrees x 1mm.

[jdm]

24 minutes ago, VWatchie said:

I have a good crystal press but I need to research what "crown type dies" are.

That's a die that has only the outer diameter, to avoid pressing on the center of the crystal and minimizing chances of breaking it. That is particularly important with crystals 1mm thick and less.

Below pictured are two generic flat mineral glass crystals. Top is 0.7 STK, bottom a 1.5mm Cousins label. Both have a slight chamfer on both sides, which allows to easily install into a nylon gasket of the correct size.

Speaking of sizes once again I never had a problem fitting any of these without worrying about to cents of mm (a novel measurement unit with the outstanding property of being 2.5 times smaller than a "thou"). That is because a nylon gasket has a certain compressibility.

 

Edited June 5, 2020 by jdm

[VWatchie]

12 minutes ago, JohnD said:

Be VERY careful if you remove the crystal gasket, the nylon ones are very brittle and can break! I would be more inclined to refit the old crystal then polish the case with it, and the chapter ring, in place.

Well, just excellent and very valuable info. Thank you! I was on the verge (in my mind anyway) to pry out the gasket. I'll follow your advice and will replace the crystal and case back before I clean the case.

12 minutes ago, JohnD said:

I can now confirm the dimensions as  being 30.98mm diameter and 1.9mm thick, with a heavy chamfer on one edge, approx 45 degrees x 1mm.

I'll bring out my caliper and measure it. I'll be back soon.

Edited June 5, 2020 by VWatchie

[VWatchie]

26 minutes ago, JohnD said:

I can now confirm the dimensions as  being 30.98mm diameter and 1.9mm thick, with a heavy chamfer on one edge, approx 45 degrees x 1mm.

My German quality caliper shows exactly 30.98 mm for the diameter   However, I measure the thickness to 2.58 mm. So, 0.68 mm thicker than 1.9 mm. The original crystal has a heavy chamfer (the way you describe it) on the side facing away from the case (the side with the scratches) and a thin chamfer on the side going into the gasket/case. The thickness has me a bit puzzled. The crystal extends just slightly above the grooved parts of the bezel. I wonder if it is the original crystal but for some reason I still believe it is the original crystal.

[JohnD]

1 minute ago, VWatchie said:

My German quality caliper shows exactly 30.98 mm for the diameter   However, I measure the thickness to 2.58 mm. So, 0.68 mm thicker than 1.9 mm. The original crystal has a heavy chamfer (the way you describe it) on the side facing away from the case (the side with the scratches) and a thin chamfer on the side going into the gasket/case. The thickness has me a bit puzzled. The crystal extends just slightly above the grooved parts of the bezel. I wonder if it is the original crystal but for some reason I still believe it is the original crystal.

That is almost certainly the original one. THIS one might well be a good substitute, though slightly thicker at 3mm,  not sure if the seller ships internationally...(the 31mm crystal is not listed in numerical order but  is right at the bottom of the list). I have used these people before and can't fault the crystals or their service. I did think that they listed 2.5mm thick ones but it appears they jump from 2mm directly to 3mm.

[jdm]

14 minutes ago, VWatchie said:

The thickness has me a bit puzzled. The crystal extends just slightly above the grooved parts of the bezel. I wonder if it is the original crystal but for some reason I still believe it is the original crystal.

Sorry, I did not recognize that at the beginning, your watch is a semi-diver, with a thick glass and a deep chamfer to clear the bezel. That makes it "special" and in practice justifies the relatively high cost.   If you don't want to spend you can always polish it. Otherwise if you like the domed style https://www.ebay.com/itm/1pc-2-5mm-Thick-Single-Dome-Mineral-Watch-Glass-27-42mm-Round-Watch-Crystal/302493359240

 

Edited June 5, 2020 by jdm

[JohnD]

28 minutes ago, jdm said:

Sorry, I did not recognize that at the beginning, your watch is a semi-diver, with a thick glass and a deep chamfer to clear the bezel. That makes it "special" and in practice justifies the relatively high cost.   If you don't want to spend you can always polish it. Otherwise if you like the domed style https://www.ebay.com/itm/1pc-2-5mm-Thick-Single-Dome-Mineral-Watch-Glass-27-42mm-Round-Watch-Crystal/302493359240

 

Very useful link, I'm going to have to get into non acrylic crystal polishing sometime as I have a few watches with scratched non round crystals that are almost impossible to source replacements for at any price.....