Watch Crown O-Ring Sizing

[gpraceman]

I have a crown that had an o-ring down inside the crown.  The o-ring was dried and brittle and in pieces.  I got it all out, but need to figure out what an appropriate sized replacement would be.  The crown tube outer diameter is 2.5mm.  I assume that the inner diameter of the o-ring should be slightly smaller than that, but just how much smaller?

[HectorLooi]

I guess you have to get an assorted o-ring set and trial and error it.

I got one of these tools from AliExpress recently and found that it works much better that the homemade one I made by grinding an opening it the eye of a large sewing needle.

[AndyGSi]

Is this from a branded watch and if so, which one?

What's the ID of the crown?

As always photos would help.

[gpraceman]

11 hours ago, HectorLooi said:

I guess you have to get an assorted o-ring set and trial and error it.

I got one of these tools from AliExpress recently and found that it works much better that the homemade one I made by grinding an opening it the eye of a large sewing needle.

Do you have a link for that?  I was trying to use a cheap oiler to get out the fragments.  Wasn't working very well.

 

10 hours ago, AndyGSi said:

Is this from a branded watch and if so, which one?

What's the ID of the crown?

As always photos would help.

It is from an Elgin with an AS 1902 movement.  Diameter of the crown opening is 2.7 mm.

Edited July 21, 2024 by gpraceman

[AndyGSi]

So the crown tube is 2.5mm and the opening is 2.7mm which means there's no way you'll get another o-ring back in.

Check out the link below.

https://adventuresinamateurwatchfettling.com/2015/10/12/crown-revival-seiko-6105-and-62mas-crown-gasket-replacement/

Edit

Is that photo before you removed the old o-ring?

Double Edit

Just realised the 2.5mm is the pendant tube so you'll be looking around 2.4mm
but will also need to know the O/D so it sits in the crown correctly

Edited July 21, 2024 by AndyGSi

[HectorLooi]

49 minutes ago, gpraceman said:

Do you have a link for that?  I was trying to use a cheap oiler to get out the fragments.  Wasn't working very well.

https://a.aliexpress.com/_msiUa9W

[gpraceman]

22 minutes ago, AndyGSi said:

So the crown tube is 2.5mm and the opening is 2.7mm which means there's no way you'll get another o-ring back in.

Check out the link below.

https://adventuresinamateurwatchfettling.com/2015/10/12/crown-revival-seiko-6105-and-62mas-crown-gasket-replacement/

Edit

Is that photo before you removed the old o-ring?

Double Edit

Just realised the 2.5mm is the pendant tube so you'll be looking around 2.4mm
but will also need to know the O/D so it sits in the crown correctly

Actually, that photo is after removing the old o-ring and putting in a new one.  But new o-ring is 2.5 mm ID and the fit on the pendant tube just seems too loose.  However, getting that o-ring out will likely be difficult, so I may just have to live with it and learn for the next time around.

How to determine the proper OD of the o-ring?  I can approximate it based on outward appearance of the crown.

5 minutes ago, HectorLooi said:

https://a.aliexpress.com/_msiUa9W

How well does it work to pull one out?

Edited July 21, 2024 by gpraceman

[RichardHarris123]

The tool reminds me of a crochet hook. 

[HectorLooi]

1 minute ago, gpraceman said:

How well does it work to pull one out?

If the oring is new and supple, this tool can pull it out very easily without any damage to the oring or crown.

But if the oring is hard and brittle, the only way is to soak it in acetone until you get a black goop and scoop it out with an oiler.

[AndyGSi]

35 minutes ago, gpraceman said:

How to determine the proper OD of the o-ring?  I can approximate it based on outward appearance of the crown.

I've only ever split the crown down and then measure it's ID to determine the o-ring size.

If you don't want to do that and can get a replacement in then you can measure the join of the washer to the crown.