Balance staff replacement Molnija 3602

[ManSkirtBrew]

Getting back to a pocket watch I've had forever. It had a broken balance pivot, so I decided to try replacing it for the experience.

The actual replacement went off without a hitch. It seems to be a press fit into the balance and not riveted, so I just had to close up the hole in the balance hub a tiny bit with a domed stake to get a tight fit.

The problem now is the roller table slips right over it with no friction.

Because the roller table is so tall, I don't think using domed punches is the way to go, but I've never done this before so I'm looking for advice. What's the right thing to do here?

Removal:

Installation:

[LittleWatchShop]

My experience is limited, but even so, I have seen this.  A previous watchmaker tried to solve it by punching the side of the roller table, like tightening a cannon pinion. Bad. I ended up replacing the roller table.

You may have to find another staff that fits.

Somewhere on this forum someone suggested inserting a whisker to fill the gap.

 

[nevenbekriev]

I can asure You that this is a staff that needs riveting. Closing the hole usually leads to loosing the center. so the balance will probably be good out of true now. As You have nothing to loose, there is a simple way to solve the loose roller problem: use (small qantyty of) superglue or thread fixer.

Edited April 4 by nevenbekriev

[Kalanag]

Might be of interest:

Balance staff: is this a decent quality?

I bought a staff for my 3602 and found the roller table not fitting. The OD was several 100th of a millimeter to big. All other dimensions were perfect.

Edited April 4 by Kalanag

[Nucejoe]

  I am guessing you bought a wrong staff to begin with.

Molnija made , no shock protection, incab, flat and overcoil. 

 

 

[nevenbekriev]

Well, 02 in 3602 means 'no shock protection, small seconds hand'. For sure there is only one balance staff for 3602, so no way to order wrong one, but spare parts from the last years of the production are wid bad quality.

I would advice to true the balance and check how it behaves in the movement without the roller first. To see if the endshake is normal and the balance position against the lever bridge, because in Molnia the distance between the balance and the lever bridge is verry small and if not trued, the balance may rubb.

[ManSkirtBrew]

Thanks for the advice, all. Yeah, I bought these staffs off eBay and I think they shipped from the Ukraine. It was a couple years ago, so my memory is a little hazy.

I do have two, so I'll put a micrometer on them and see if the other is any different.

And yes, that was clearly my mistake on the not riveting. I thought with the step sat flush with the other side and thought there's nothing to rivet, but I was mistaken.

This is why I'm practicing on a cheap eBay find.

Here are a couple close ups of the other replacement staff and the one I just installed.

[watchweasol]

Hi. There is definitly an undercut on the hub for the wheel to be riveted in as normal.  Must admit some do look flat but it needs careful looking at

[JohnR725]

5 hours ago, ManSkirtBrew said:

micrometer on them and see if the other is any different.

unless you enjoy surprises always best to measure the new and the old staff to see if there any differences.

 

[ManSkirtBrew]

2 minutes ago, JohnR725 said:

unless you enjoy surprises always best to measure the new and the old staff to see if there any differences.

 

That would definitely have been the smart thing to do.

Unfortunately, I'm not always the smartest tool in the shed.

[Nucejoe]

On 2/15/2022 at 4:18 PM, nickelsilver said:

I really strongly recommend not using a micrometer to measure balance staff pivots. By the time you can feel that the spindle and anvil are in contact, you have marked the pivot with a couple of tiny flat spots. I know some people say the spring loaded dial type tools like the JKA Feintaster won't mark pivots, but I don't trust that. For stuff under about 0.15mm you really need a jewel gage. I know they are hard to find and expensive, but those little flats will really mess up your timing.

Attention those of us who want to make a micrometer from scratch, don't, 

GET A JEWEL GAGE, 

Harmful to be creative. some of the time.

Edited April 4 by Nucejoe

[ManSkirtBrew]

Okay, I got the staff riveted in properly. Before resorting to super glue, I did a search on Youtube and found this video that uses a weird faceted stake to tighten up the roller table.

And what do you know, I have one in my set. Gave it a shot, and it worked a treat.

Now I have an excuse to buy the truing calipers I've wanted.

 

[nevenbekriev]

Good!

5 hours ago, ManSkirtBrew said:

Now I have an excuse to buy the truing calipers I've wanted.

 

Use the stacking set instead.

[ManSkirtBrew]

Got my calipers and made the balance as flat as I could.

So it was time to assemble, and when I pressed the hairspring on, I noticed it was super wonky. There was a pretty hard bend and a bit of a twist near the stud.

At first I thought maybe it was supposed to be there, but after looking at the path of the regulating pins, it seems much more likely that it was bent to begin with, or I bent it taking it apart a few years ago when I was less experienced and even more prone to ruining parts than I am now.

Which is saying a lot.

So out came my #1 and #6 tweezers, my favorite hairspring bending tools. It also needed a little twist and adjustment near the overcoil to get the collet centered, but I'm pretty happy with the results. I know the terminal curve could be more perfect, but I had to call it at some point.

Final assembly soon!

 

Before:

 

During:

 

After:

[LittleWatchShop]

I call it excellent work!

[nevenbekriev]

Waiting wor the result of the free oscillations test. In this calibre it is normaly about 200

[ManSkirtBrew]

Well, there aren't enough frames to count, but it oscillates for a good 30 seconds or so with a puff of air.

I have to say, for my first balance staff replacement, I'm pretty pleased with these results. I know, show me other positions. Maybe after dinner

\

 

Edit: well I was right about needing to see other positions. The hairspring is definitely hitting something in positions other than dial down--you can hear it when you put it to your ear. The overcoil probably needs more tweaking.

Which I'm not going to do right now. Maybe some time in the future when I'm ready for more hairspring practice

I did close up the minute hand, since it was freewheeling, and get it cased back up.

Edited April 14 by ManSkirtBrew