Got a nice old Hampden 108 on the bay, clean and smooth running.
After cleaning and lubricating I put it back in a case, wound it up and it started on it's own after two winds, and as I approached full wind, "SNAP" and she quit.
Broken balance staff!!!!!
What happened?

Bad balance jewel?

Did the mainspring break or come off the arbor?
RR

Thanks for the help guys,
I haven't torn it back down yet, but this sure is frustrating. I'll let you know what I find.

I would bet the staff was already bent or broken and did not show that until the shock of the main breaking made it jump out of kilter.

If the safetly pinion has let loose, it is for sure that the balance staff was already a bit on the sick side.

The shock of the main breaking without the safety pinion releasing would stop at the escapment wheel which would be badly damaged and possible knock about the pallet fork jewels.

My guess is a broken or cracked jewel which put the staff out of whack. (Not an approved horological term) In my experience you could have a cracked or broken jewel which still worked but something made it worse and now a bad staff.

First off, thanks guys for the helpful thoughts.

Just tried to wind it to see if the mainspring was broken... it's not. It winds okay.

So, I took the hands and dial off... removed the balance cock assembly...looked for broken pivot or jewels and couldn't see anything wrong!!

Put the balance cock assembly back on and the watch is running perfectly!!
I assumed last night when it stopped that a balance staff was broken because I could see some wobble in the balance wheel.

Now, I don't know what to think or do.

This all started with trying to fit the movement into a spare case. And the stem in the case would not release far enough to set the time. So, I adjusted the stem sleeve to accommodate winding. But it still does not wind as easy as I think it should. Winds fine outside the case. Not sure how to adjust for that. Anyway, I took the movement all apart to clean and oil and noticed the winding mechanism a little gummy, assumed that was why it didn't wind easily. Cleaned it all up - oiled it and put it in the case. That's when she went "SNAP" and I thought I'd broken the balance staff when I saw the balance wobble (slightly).

Suggestions, thoughts, precautionary prevention ideas, all appreciated.

It could be that the mainspring slipped on the arbor and then re-hooked itself on the next turn. This does not mean that the jewel is OK. Check the safety pinion as David suggested. Pull the Pallet fork out and make sure you have good kickback and reassemble it again.

I would go along with deacon here that there is probably a chipped staff jewel on one side or the other. It was probably already that way and just not noticed... it may be chipped only in one direction where it will run fine until tipped or touched in the direction of the damage to the jewel. this is when you will see the "wobble". The gummyness of the movement may indicate that the mainspring click may not have caught, allowing the mainsprings to unwind whatever amount you had just wound it... Thats the only thing that makes sense to me with what you are giving us for information as happening.

Patrick wrote:

Pull the Pallet fork out and make sure you have good kickback and reassemble it again.

Not sure how to do what you suggest here. When I had the balance out, I checked the pallet movement, and it did move back and forth sharply with the escape wheel, and appeared to be normal. Would that be "good kickback"?

Regarding the mainspring, what you suggest seems to have a lot of merit. I have not had the mainspring apart. It may well be gummy inside and there was two subsequent snaps when it happened. One might have been disconnecting from the arbor and the other reconnecting.

And right now, it's running face up on the bench, and I haven't moved it.
I've got a 10X loupe coming, when I get it I can inspect the jewels closer. Meantime, I'll take out the mainspring and see what it looks like inside.

Really appreciate your help guys. I'll give you an update when I get the new loupe to inspect the jewels, and also when I get the mainspring apart.

Dave,
If you have Fried's book it Explains kick back. Wind the watch 1 turn and at the end of the spin it reverses its direction of spin, then you have kickback. You must have the fork removed to accomplish this.
You may leave the escape wheel in but the fork must be removed to do this. That 10x loupe is going to be a bit powerful for work. I use a 4x and it is fine.