Balance poising (static)

[LittleWatchShop]

I have this Cyma pocket watch that has wild variations in various positions.  I pulled the balance to check poise and I can definitely see a heavy side.  Here are pictures.

Notice the small screw opposite a larger screw.  The smaller screw is the HEAVY side.

Does this seem odd??

[nickelsilver]

It seems that an attempt to correct the poise was made in the past; if it was at the factory I would think it would be poised without a clear heavy spot, but if it was restaffed, and the staff was a bit undersize for the balance (could be from punching out the staff, or a poor replacement) that can introduce a large poise error as there's no assurance the staff rivets in perfectly centered. Perhaps someone tried to get it better and stopped before it was right.

 

If there's the slightest bend in a pivot that will show as a large poise error. Pivots should be cleaned in clean pithwood, and the ruby jaws of the poising tool likewise cleaned (the pith batons are nice for this). Tool should be level, and make sure the jaws are on the cylindrical part of the pivots, not the cones. I know that all sounds obvious but I've seen grads from watch school not check all the above...

[Nucejoe]

1 hour ago, LittleWatchShop said:

 wild variations in various positions.  

Was variation in horizental positions  " WILD "   too?    

[LittleWatchShop]

Just now, Nucejoe said:

Was variation in horizental positions  " WILD "   too?    

Embarrassed to say...I don't remember.  I should have done all positions and wrote it down...that is the way I was taught in engineering school--don't rat me out!!

[Nucejoe]

8 minutes ago, LittleWatchShop said:

Embarrassed to say...I don't remember.  I should have done all positions and wrote it down...that is the way I was taught in engineering school--don't rat me out!!

So we have no way to rule out any of the IFs Nikcelsilver listed, ie; poor restaffed, bent pivot , who knows could even   badly fitted roller table.

Just now, Nucejoe said:

So we have no way to rule out any of the IFs Nikcelsilver listed, ie; poor restaffed, bent pivot , who knows could even   badly fitted roller table.

Come to think of it ,  roller table wouldn't introduce much imbalance.

[LittleWatchShop]

I chucked it into a balloon chuck ti see if either pivot was problematic.  One of the pivots did seem to have an ever so slight bend at 30x magnification.  Maybe that is enough to cause the issue.

On the poising tool, using 10x magnification, I could detect a bent pivot effect.  I played around with counter weight using rodico and the balance performed much better. 

Will continue to study and report back.