Bent Balance Staff Pivot?

[jaycey]

Guys I am having trouble with a Smiths 27-CS movement.

 

I have serviced it and had to do some work on the hairspring. That is now a nice shape, flat and round ;)

Trouble I am having is that as soon as I engage the balance shock retention spring it either slows to a crawl or usually just stops.

 

I have had a good look at the jewels and there are no cracks or wear. I can's see any noticable bend in either pivots and the watch runs absolutely fine unitl I engage the retention spring.

The only thing I can think of at the moment is a bent pivot that I can's pick up on with the eye. The jewels are not wobbling before I engage the spring.

 

Or, somehow the top of the pivot it making contact with the cap jewel?

 

Any tips or tests I can do to work towards a solution?

[bobm12]

I don't know much but maybe the cap jewel is upside down? You know, one side, the one that goes towards the pivot is flat and the other one is rounded...just my 2 cents.

 

Cheers,

 

Bob

[clockboy]

If it was running OK before the service then Bob is probably correct. If not then something has been bent either the pivot or the balance bridge. As a test try a little piece of packing under the bridge before reassembly. If it shows improvement then is highly likely that it is the bridge has been bent.

[jaycey]

Thanks for the replies guys.

The cap jewels were definitely in the right way around.

With the cap jewels removed I put some pressure on the jewel bearing and it didn't effect the running of the watch so the pivot had to be hitting the cap jewel.

 

This was a watch I purchased when I had only just started Horology Training and it came with a shock jewel missing "a easy fix" as it was sold to me (I can hear the chuckling!)

So I sourced a replacement shock jewel assembly and put it in and the watch started ticking...but not for long. It had very poor amplitude.

I put it in the cupboard and forgot about it.

 

Fast forward a year or so, got it out, sorted out the poor shape of the hairspring, serviced it and was left with this problem.

 

Thank you clockboy, I cut a thin piece of plastic and put it under the balance cock and voila, it's running a treat now. On a stop watch it has gained 5 seconds over the last 3 hours without any regulation and that's on the wrist.

I will take it into class tomorrow and put it on the timegraph.

 

Conclusion, either I sourced the wrong size shock jewels or as clockboy says "the balance cock is bent"

 

It's one of my personal watches so it can stay bodged for now ;)

 

Cheers guys.

 

[clockboy]

Good its now running I trust you gave the jewel a drop of oil in its middle.

Most use Moebuis 9010 for this

[jaycey]

I did indeed, the only thing I haven't oiled yet is the pallets. I have some 941 in class for that.

Dial up all night it is about 45 seconds fast.

 

Happy days :)