Bent Balance Cock

[Scouseget]

I am currently servicing a Regina, circa 1890, size 16, pocket watch for a friend. It looks like it's been a bit butchered over the years with superficial damage to the plates, probably caused by using poor quality, or wrong sized, screwdrivers, and general careless handling. Anyway, I dismantled, cleaned, lubricated, and reassembled it only to find that the balance flops around and in fact the pivot doesn't even enter the cock jewel hole. The balance staff is in perfect condition (I haven't replaced it), the jewels are in good shape with nothing broken, the jewels are fully seated, and the cock is also fully seated and screwed down to the plate. Upon closer inspection, I could see that the balance cock appears to be slightly bent upwards, thus creating more distance between the jewel holes. I'm not reluctant to admit when my inexperience has caused damage to a movement but I don't think that's the case this time as if I'd bent the cock, I think it would have been bent down, not up, therefore I have to assume that a previous repairer must have done this for some unfathomable reason.

Do you think this is likely and have you ever encountered such a weird problem before? More importantly, how can I fix this problem, i.e., how should I straighten it? My gut tells me to let the ends straddle a couple of blocks, then apply pressure in the middle to bring it back to straight, however I'm concerned that I may break it (it's non magnetic so I'm guessing it's plated brass?), And what happens if I over bend it as I'm sure that thousandths of an inch count with a watch movement, and this sounds like a brute force fix so any advice you can give will be much appreciated. If I do over straighten it and therefore reduce the distance between jewel holes to less than the balance staff length, can I shim under the foot of the cock to adjust the distance as I can use brass shims that will allow fine adjustments, much more so than trying to bend the cock itself?

Perhaps I should  over straighten it deliberately than adjust to the correct distance using shims as a matter of course? This sounds crude but I think it will give me the possibility of finely adjusting for the right end shake, even though it won't be exactly elegant, though the shims will be hidden under the balance cock foot. 

Thoughts and suggestions will be greatly appreciated - thanks in advance as always.

 

[anilv]

I would remove the balance from the cock and remove balance assembly.

Place the cock on a piece of cloth on a hard surface. remove all the jewels and regulating stuff, lay the cock top-down on the cloth. Apply pressure on the underside of the cock, the cloth will give slightly but will give some protection against over-bending.

Check fit by installing the balance/ cock.. You do not need to fit the balance to the cock at this time. repeat as necessary.

rgds

Anil

[szbalogh]

Usually balance cock is not to be bent. More acceptable way to adjust endshake on such old movements is to dig up a bit the plate under the cock on the desired side. This will move some material over the base plate plane and lift one side of the cock. You can then file down the excess to adjust proper endshake. I have never done but seen this many times. Can be an option. I can post pictures later at night (at around noon at You  )if you need it.

Edited July 29, 2016 by szbalogh

[anilv]

szbalogh... these 'flea bites' can correct some end shake but if the cock is visibly bent then it needs to be brought back so that it's at least in the ballpark.

In this case the pivots don't even reach the jewel holes.

 

Scouseget,

I just had a thought.. did you check if the balance jewel settings were correct..ie not too deep in the plate?

 

Anil

[wolfwatchwerks]

Realizing this post is a bit old but, I would add that I had the same problem on an Omega 39.5L. Everything you stated but observed end shake of about 1- 1.5mm. Upon repeated disassembly, reassembly I had noticed a slight bend in the cock. Bend was about.....0.5 degrees the bridge on this model is quite thin and can bend easily if not removed carefully/properly. I removed the regulator and end, pivot jewel and bent the bridge in a downward angle(very, very carefully) and repeated until the regulator was sitting flush with the cock. One way to quickly tell if you have a bent BC is to observe the regulator arm and the surface of the bridge and see if there is either a gap (bridge bent up) or if the tail of the regulator is lifted, the BC is more than likely bent too far down. Once I returned the bridge to its proper position end shake was reduced to about 0.1-0.2 mm nominal. Twisted collet to beat and now runs just fine. In short, yes have had this problem as well, and a bent balance cock was the culprit.

[rogart63]

You have no other option but to try to bend it back. If you fail you could maybe try to find a donor movement? 

[vinn3]

bending AND alignment;  this requires care, experience and good tweezers and plyers. you can do it.  vin