Monday, 9 April 2012

Molnija 3602 balance repair

I'm writing this post in response to a reader's question that asked if I could give them some advice on how to correctly attach the balance spring and shaft on a Molnija 3602.

To start, if you're trying to restore a Molnija and you don't have the proper tools, then buying a parts movement on eBay is the easiest, cheapest and best way to get your watch back up and reliably running.

If you do need to re-attach a balance spring to the staff and you don't have the proper tools, you could use very fine pliers to re-crimp the spring collet. Depending on the quality of the balance spring collet (dented, rusted, etc) this may not be an option. There is NO guarantee that this method will work or that it will produce reliable results or that you'll have anything more than a paperweight when you're done. It is also the easiest way to damage a balance spring - which are sooo easy to mess up even when you're being super careful.

In principle, if you can drive the balance spring collet onto the balance staff, in perfect alignment, and maintain sufficient friction between the staff and the collet, then you can complete the repair. This is much easier said than done, and the proper tools make the world of difference.

The goal: to join these three items - the balance spring & collet, the balance staff, and the balance wheel. These items were kicking around my parts draw - you may notice that the balance wheel is a little deformed, after I took this first photo I used a flat punch against an anvil to flatten it out.

Closeups (as good as my camera can manage):

 As I mentioned in a previous post my staking set does not have a full compliment of anvils, so I've used the best anvil that I have at hand to drive the balance wheel and staff together prior to riveting.

Step 1: Driving the balance staff and balance wheel together. Align everything. Select the anvil carefully, I've used a flat faced punch to gently tap the two items together. I have to emphasise just how little force needs to be used, the balance wheel can very easily be ruined..


 Step 2: Riveting the staff to the wheel. A domed punch/stake can be used to peen over the lip on the staff which will then fix the wheel to the staff.


 Examine the quality of the work, checking the wheel for trueness, etc. (I'm not going to put this in a watch any time soon, so I haven't bothered perfecting the wheel's poise/trueness).

Step 3: Driving the balance spring collet to the balance staff. Again, alignment is critical, as well as the correct selection of the stake. If the collet on the inside of the balance spring is loose on the staff, a concave stake may be able to shrink it, but then this also may damage the inner edge of the spring. If you're feeling like a rebel (with the right tools), fine pliers might do the job. The collet should have a tight friction fit and not a rivet fixing onto the staff.

Job done! Fix it to the balance cock & see how it runs. Because Molnijas have a regulator stem, you've got a little margin to correct the orientation of the collet in relation to the staff. However, it is still always best to align the entire job (wheel, staff, spring), otherwise you may install the balance and find that it wants to sit 20 degrees from the lever and simply wont engage it.

1 comment:

  1. Okay this helps some, my problem is that I bought a watch and the balance wheel is not installed right... How do I check this and correct it? Namely the put the dang thing back in the watch right. Any help will be greatly appreciated, so thanks in advanced.