Crowns For Old Watches

[Davey57]

I am needing 3 gold coloured crowns to complete some old watches that I am restoring. I have been in touch with a company that specialises in old parts that can supply them. But they are also quoting for the tubes. 2 of the watches are Felsa 1560 but one has tube diameter of 2.0mm and the other is 2.5 I mentioned this when I asked about them so maybe that is why the tubes are included but I don't understand how that will work. Could I not find a couple of crowns from Cousins that will match my required sizes? I am not sure about the thread sizes of the stem though.

[rogart63]

You need to now what diameter the crown should have? And then the width? Example 5x3 mm. And then you need as you say the crown tube size. Usually 2 or 2,5 mm. The thread size is as follows. You measures the diameter of the stem. Here is a size chart from Esslinger . http://blog.esslinger.com/stem-tap-mm-size-cross-reference-chart/ 

Most common are Tap 10 and tap 9 .

And buy new ones as some NOS could be dry or the o-rings rubber  could be sticky .

This is a popular shape on old watches. 

https://www.cousinsuk.com/product/swiss-domed-gp

Tap 9 first and the diameter and tubesize. All you need to now? 

Edited March 8, 2016 by rogart63

[Davey57]

Well that is everything I wanted to know, I have often wondered about sizing crowns to stems. Many thanks for that.

Just had a quick look at the link for Cousins and I will dig deeper a little later but, it looks as if the tube diameters listed only got to 2mm on that page.

[rogart63]

Well that is everything I wanted to know, I have often wondered about sizing crowns to stems. Many thanks for that.

Just had a quick look at the link for Cousins and I will dig deeper a little later but, it looks as if the tube diameters listed only got to 2mm on that page.

Didn't see that?Ooops .But i think you could find some other on the other pages. 

[Davey57]

No worries at all, now that I know what I am looking for I am sure to find something.

Thanks again.

[Davey57]

Well I thought I knew what I was looking for. Sorry if this is a lame question but, I have measured the threaded portion of my stems and one is 0.86 and t'other is 0.84. Looking at the stem tap chart 0.80 is tap 11 and 0.90 is tap 10. Mine are right in the middle of the two sizes. To confuse me even more Cousins list tap size 8 = 0.80 / 9 = 0.90.

Somewhat befuddled.

[StuartBaker104]

Davey,

Felsa1560 is 0.9mm (check windingstems.com).

You will need a size 9 from Cousins for this. If you feel the stem thread is worn, Cousins have these available.

Rgds

S

[Davey57]

Many thanks. Looked at w/stems .com. In their diagram is measurement D the stem diameter for the crown then?

I still don't get why Cousins sizes differ from the ones given in the Esslinger chart.

[StuartBaker104]

Davey,

Yes, diameter D is the major diameter of the thread.

The reason that there are different standards is that there was a time before the world was unified! I once came across a table of comparisons of miniature thread sizes, I can't find it now, but there are many. US watchmakers used a scale where bigger numbers meant smaller threads.

Most watch parts today use unified miniature (UNM), minimum diameter for a 0.9mm thread is 0.867mm. All Cousins parts are listed this way, but most suppliers provide a table so their standard is clear. Just be careful not to mix your measurements if buying from multiple suppliers.

Reds

S

[Davey57]

Thanks Stuart, that's very helpful.

Learning all the time.

Dave