Main Spring Help Needed, Unsure What To Do.

[BeyondWorld]

Hello people.

 

So I'm repairing an old 1920's wristwatch, I've taken the main spring out, which is broken.

 

And I've come up with these measurements. 

 

1.64 mm height

 

0.16 - 0.18 mm thickness (Pretty sure it's 0.16 mm, 0.18 mm read out was when I was unable to get a straightened measurement.)

 

520 - 530 mm Length. 

 

17.44 mm Inner Barrel 

 

I've looked on cousins and the closest that comes to it, are these:-

 

1.65 x .16 x 440 x 14 Non-Automatic

1.60 x .16 x 540 x 15 Non-Automatic

1.60 x .16 x 580 x 16 Non-Automatic 

1.60 x .16 x 580 x 16 Non-Automatic

 

Which is what my problem is, they aren't really that close at all.

 

So I'm not quite sure if one of these will do or not.

 

[rogart63]

What movement is it? Have you looked on Rantff http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&2&2uswk. On some watches you can see the size of the mainspring . 

Check with clockboy i think he has the general ressorts mainspring catalog?

Edited November 29, 2015 by rogart63

[BeyondWorld]

I can't identify the movement, it's unsigned swiss made, patent depose on movement, and on case, which means nothing.

 

Nothing is signed on the dial and nothing is under the dial plate.

[rogart63]

I think you should be looking at the Dennison sizing mainspring . Size 7,5 is  1,65 and 0,17 is 6 and length is in inches . which should be around 20-21 inches . 7,5 x 6 x 20-21 . 

Bed time reading . Have no answer where to get the right spring . But this maybe will help :)

http://www.watkinsr.id.au/mainspring.pdf

Edited November 29, 2015 by rogart63

[BeyondWorld]

Would you happen to have a link handy?

 

The only one I can find on cousins that is 1.65 and 0.17, is this one, "Mainspring, 1.65 x .17 x 440 x 15 DBH End" and not only is it too short, it has the wrong end.

[BeyondWorld]

Okay, cheers, thanks for adding the link. I've had a quick glance at it, and will see if it can give any clues into sourcing an old one.

 

I think I'll probably have to go with "Mainspring, 1.60 x .17 x 520 x 15 Non-Automatic". As it seems the closest that's available.

 

Mainsprings are a bit more forgiving, so hopefully it won't have much of an effect on how the movement runs.

[JohnR725]

I have the general ressorts mainspring catalog and there is a problem  with the size you have.. There are almost no mainsprings with a width of 1.65 mm  in the catalog there's only 26 listed versus several pages of the 1.60 with. So in the catalog for the 1.65 a lot of the springs are American which means that ends are going to be possibly different. Then none of them are long enough the longest one in this width is 480 mm. If you go to 1.60 mm with .16 for the thickness there is a 540 mm. Which I believe is the second spring on your list.

 

Then just because the catalog shows something doesn't mean it exists anymore..So looking at the length of 520 and width of 1.60 For each of these thicknesses they did have a spring that existed..  17  part number 4655, .18 part number 4674  and .19 part number 4688.

 

Then there is always the other little problem in finding mainsprings what makes you think the original is the original spring?

 

What is the size of your watch?

 

So for the width of 1.60 Versus 1.65 that's not going to matter much. Then if it's a blue steel spring the modern springs tend to be stronger so you can sometimes get by with a lighter spring today. Then the Length of the spring determines running time so If it's too short you are going to decrease the running time too long and that also decreases running time as there is no place to wind the spring up if the barrels full. 

[rogart63]

Check this out . http://www.daveswatchparts.com/SwissMainsprings.html

[BeyondWorld]

@JohnR725

 

"Then there is always the other little problem in finding mainsprings what makes you think the original is the original spring?"

 

That's a good question, I'm not 100% sure it's the correct mainspring. It is likely near to be 100 years old, so I have no idea on it's history.

 

I can tell that it's a old mainspring though and not a new one.

 

"What is the size of your watch?"

 

The watch size is 38.24 mm, and the movement size is 36.17 mm. Most likely a small pocket watch movement. Though the watch itself is a proper wristwatch, and not one of these modern recased watches you see on ebay.

[JohnR725]

The reason I asked the size of the watch is in the mainspring book some of the watches had a size reference.

 

Then for identifying your watch you should post a picture it's possible somebody might recognize the watch..

 

Other ways to identify a watch  is by the setting parts they form  unique fingerprint system.. All you need to know is the size your watch in Lignes which is about 16. Then you need the right material catalog  that shows the  parts for that I've scanned A PDF attached.. Although they have made so many watches the chance of identifying every single one is not always possible..

 

Even if you can't identify the watch there are calculations for figuring out the mainspring. For that I've attached a PDF.

 

https://en.wikipedia.org/wiki/Ligne

 

http://members.iinet.net.au/~fotoplot/tech/wmms.html

Bestfit.PDF

watch mainspring calculation.PDF