Jump to content

ST1686 Barrel and Mainspring Question


Recommended Posts

Hi All!

I have an ST1686 that I am tearing down and rebuilding for my first service.  I got down to the mainspring barrel and opened it.  It was pretty dirty, so I unwound it to clean.  But it didn't look like a mainspring typically would like this stock mainspring photo from Wikipedia.  It was only spiral coiled and didn't flatten out.  I've attached a photo to accompany my poor rookie explanation.

If this is abnormal, I'll need to source a replacement.  I see that the ST1686 takes a GR4486, but the GR4486 is discontinued.  I'm able to source a new old stock (NOS) spring on eBay, but what would be a good modern alternative to the GR4486 1.60mm high x .10mm thick x 300mm long x 9mm barrel diameter?  Do I look for slightly longer spring? Thinner spring?  Thicker spring?  I know the height and barrel diameter should probably need to stay the same, right?

As far as the barrel goes, how do you tell the difference between the machined ridge to hold the end of the mainspring and a broken piece of mainspring that's stuck inside of the barrel?  I've attached photos of the end of the mainspring and the inside of the barrel.  I appreciate the help since I have no bearing for what "normal" looks like.

Thanks for the help in advance!

Dave

IMG_1566[1].JPG

IMG_1567[1].JPG

IMG_1565[2].JPG

IMG_1568[1].JPG

Link to comment
Share on other sites

Older mainsprings look like that. The S shaped mainspring is a modern invention that is, as far as I know, better at providing the same torque across all states of wind. By modern I mean 1950-ish (someone will correct me on that I'm sure).

Your old spring looks ok to my eyes: no kinks, healthy space between the coils. I'd just put it back, though others might replace it.

  • Like 1
Link to comment
Share on other sites

It all depends how much you're willing to spend and if you're happy to try the old mainspring
and see what results you get with the possibility of having to swap it at a later stage.

The key sizes are the height and thickness with some flexibility on the length depending on the barrel size.

If you look at the likes of Cousins for springs around the GR4486

image.thumb.png.3585248c4fe2c32ab8ca67ae6ddd4126.png

Edit

There are still some GR4486 out their.

https://www.ebay.com/itm/126715574424?ff3=2&toolid=10044&customid=&lgeo=1&vectorid=229508&item=126715574424&ufes_redirect=true

Edited by AndyGSi
  • Like 1
Link to comment
Share on other sites

welcome to the forum, @akira7799

you could also go for this spring, available at Cousins:

image.thumb.png.cdacf4cf841289e46fd0ded51ed25dd7.png

 

I sometimes find that it's good to go down in strength (height or thickness) ever so slightly, when going from an old spring to a new S-shaped one + upgrading to new synthetic lubricants. You may otherwise risk re-banking (if everything else in the movement is doing well).

 

Link to comment
Share on other sites

Re using the spring that comes out is always worth trying. If everything else is in good working order and the train and escapement are running with as little friction as possible then this spring could very well perform adequately. I would never put in a stronger spring to overcome excess friction. It would be wonderful if there was somewhere a list that held the torque rating that a spring should have and a device with which to test it....available to us mere mortal watch repairers...very wonderful indeed 🙂

Link to comment
Share on other sites

I recently finished 2 1686 watches, a “Cardinal 17 jewel” and. Delaware 17 jewels.”Both had mainsprings like the one you showed.  I replaced them with new style for Caravelle 10-OAC which were listed as acceptable for replacement.  Both are running well.

Link to comment
Share on other sites

I remember reading that it isn't advisable to put an old blued mainspring back into a barrel as there is a good chance it will break at some point and cause further damage.  But that spring looks to be an alloy spring.  I would put it back in and see how the watch runs

Link to comment
Share on other sites

10 hours ago, Knebo said:

welcome to the forum, @akira7799

you could also go for this spring, available at Cousins:

image.thumb.png.cdacf4cf841289e46fd0ded51ed25dd7.png

 

I sometimes find that it's good to go down in strength (height or thickness) ever so slightly, when going from an old spring to a new S-shaped one + upgrading to new synthetic lubricants. You may otherwise risk re-banking (if everything else in the movement is doing well).

 

@Knebo, thanks for the spring recommendation.  I’ll have it in my hands in a few days.  These springs are pre-lubrocated, correct?

11 hours ago, fellerts said:

Older mainsprings look like that. The S shaped mainspring is a modern invention that is, as far as I know, better at providing the same torque across all states of wind. By modern I mean 1950-ish (someone will correct me on that I'm sure).

Your old spring looks ok to my eyes: no kinks, healthy space between the coils. I'd just put it back, though others might replace it.

@fellerts, thanks for the info.  I now know the difference between will and new style mainsprings.  As I wrote above, I’m going to go with a new spring.  I don’t want to have to tear down an entire movement again if the spring fractures in the future.

11 hours ago, AndyGSi said:

It all depends how much you're willing to spend and if you're happy to try the old mainspring
and see what results you get with the possibility of having to swap it at a later stage.

The key sizes are the height and thickness with some flexibility on the length depending on the barrel size.

If you look at the likes of Cousins for springs around the GR4486

image.thumb.png.3585248c4fe2c32ab8ca67ae6ddd4126.png

Edit

There are still some GR4486 out their.

https://www.ebay.com/itm/126715574424?ff3=2&toolid=10044&customid=&lgeo=1&vectorid=229508&item=126715574424&ufes_redirect=true

@AndyGSi, thanks for the link to the NOS spring.  I’ll feel more comfortable going with a newer technology spring though.

10 hours ago, Neverenoughwatches said:

Re using the spring that comes out is always worth trying. If everything else is in good working order and the train and escapement are running with as little friction as possible then this spring could very well perform adequately. I would never put in a stronger spring to overcome excess friction. It would be wonderful if there was somewhere a list that held the torque rating that a spring should have and a device with which to test it....available to us mere mortal watch repairers...very wonderful indeed 🙂

@Neverenoughwatches, thanks for the info on the old spring.  It’s good to know that I shouldn’t get a more powerful spring.

8 hours ago, ColinC said:

I remember reading that it isn't advisable to put an old blued mainspring back into a barrel as there is a good chance it will break at some point and cause further damage.  But that spring looks to be an alloy spring.  I would put it back in and see how the watch runs

@ColinC,im just going to upgrade to a newer spring.  Out with the old, in with the new.  How can you tell the difference between  blued spring vs. an alloy spring?

Lasty, for everyone, how can you tell that the barrel arbor key is properly seated in the spring center?  Is it visual inspection? Do you turn the arbor to make sure there’s a positive connection?  Does it happen “on its own” once the spring is placed in the barrel?

Link to comment
Share on other sites

7 hours ago, akira7799 said:

These springs are pre-lubrocated, correct?

Yes, you can insert that one from the metal ring and you're good to go. Some people still add a few drops of oil on the spring -- I don't.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



×
×
  • Create New...