Troublesome automatic mainsprings- a simple solution

[Bill241]

I’ve been servicing my 1962 Omega Seamaster, with the sturdy cal 562 automatic movement. 

As part of this, I decided to replace the mainspring with a new one. Two were ordered from Cousins, and neither would go in to the barrel from the aluminium ring with the aid of the rounded end of my brass tweezers (I don’t have a mainspring winder). In both cases, despite careful efforts to seat the bridle first, there remained part of the spring sticking out. I removed both springs and tried to hand fit them. Whilst this technique is generally ok with most non-auto springs (in my experience), these automatic ones seem to be made of a soft alloy that deforms easily.

My simple solution  was to make a plunger on the lathe from a piece of 10mm brass rod, using the discarded GR aluminium rings as a size guide. I’ll use the jewelling tool to fit the next spring, hopefully with more success. 

[Jon]

I'm interested how this pans out. I like that you're making a tool to suit this situation rather than buying a set of winders!

[mikepilk]

I'm not sure why it didn't work. I too use brass tweezers. First I use the flat handle end to push the spring down flush with the ring, then use the tips to start pushing the outer coil in to the barrel, starting at the  bridle. I've never had a problem doing it this way. 

Why not re-use the springs? Have a look here :

 

 

[Knebo]

8 hours ago, Bill241 said:

I’ve been servicing my 1962 Omega Seamaster, with the sturdy cal 562 automatic movement. 

As part of this, I decided to replace the mainspring with a new one. Two were ordered from Cousins, and neither would go in to the barrel from the aluminium ring with the aid of the rounded end of my brass tweezers (I don’t have a mainspring winder). In both cases, despite careful efforts to seat the bridle first, there remained part of the spring sticking out. I removed both springs and tried to hand fit them. Whilst this technique is generally ok with most non-auto springs (in my experience), these automatic ones seem to be made of a soft alloy that deforms easily.

My simple solution  was to make a plunger on the lathe from a piece of 10mm brass rod, using the discarded GR aluminium rings as a size guide. I’ll use the jewelling tool to fit the next spring, hopefully with more success. 

Hi @Bill241, 

Yes...SPECIFICALLY for these Omega calibres (55x, 56x), there are several GR springs that are supposed to fit (I think Cousins sells 3 different ones that all are supposed to fit). However, some of them are literally 0.1mm too large (in their retention ring) for the actual diameter of the barrel. So yes, they won't fit straight from the ring. This is very annoying.

I can tell you from my own frustrations - as someone who's also without a mainspring winder. 

Unfortunately, for that reason, I doubt that your plunger trick will work. But I'll keep my fingers crossed for you. 

In addition, some of these GR springs also have inner coils that are too large for the Omega barrel arbor. 

These are the springs I tried:

G62040: 1.01 x 0.11 x 380 x 10.20

GR2535X: 1.05 x .12 x 340 x 10

M64791: 1.05 x .12 x 400 

GR2533X: 1.05 x .11 x 360 x 10

 

IF (and I really hope so), I remember correctly, at least the GR2533X worked right away (barrel diameter and inner coil. 

Hope this helps. 

[Bill241]

Thanks for all the replies!

I agree that Cousins’ mainspring offerings for the 550 series movements are a little bewildering. I bought one GR2628X spring, but measuring it against the old spring it was slightly too tall and too wide for the barrel. The less expensive G62040 seems to fit the bill- I’ve ordered a few more of these. 

I actually managed to fit one of the G62040 springs into the barrel and the movement has been running for two days. However, I wouldn’t want to wear the watch knowing it has a deformed spring that (through my own misadventure) has kinks/possible fatigue. I’m looking forward to trying out the brass pusher and will report back how I get on. 

[mikepilk]

When I first started and had problems pushing mainsprings out of washers, I too made a tool from some brass rod. Problem is you need the exact size for each mainspring washer. I found it wasn't useful, and much easier to push the springs out with some brass tweezers. The only problem is if the spring in the washer is too big for the barrel, as you have found.

[Bill241]

The results with the pusher are satisfactory. 

I’m not bothered about using a bit of brass rod- I’m fond of Omega 550 and the related 600 series movements, so this will get plenty of use. I’m usually successful with tweezers when fitting manual springs. But these automatic ones are something else. I might have a go at rewinding the bad ones using the washer technique, and then practice with a redundant barrel. 

[Knebo]

That's great