Barrel bridge not fitting snugly back onto movement plate

[GregG]

I have a pocket watch that I'm trying to fix up.  I noticed some sideshake in the barrel bridge, so before reassembling it fully, I staked the pivot closed and broached it open.  Pretty easy, no surprises.  But when doing a test fit of the bridge back onto the mainplate, I noticed that it doesn't want to fit back together.  There's a good half-millimeter gap between the bottom of the bridge and the top of the movement plate, and I don't know where it is originating from. 

My first guess was that the hole in the barrel bridge was closed too much and it's pushing the barrel down.  I broached it open a little more and that hasn't fixed it.  And if I remove the bridge and just test fit the barrel arbor into the bridge, it fits perfectly.  Then I thought maybe the bottom of the barrel was fouling against the movement plate, but the arbor has a shoulder on it to prevent that from happening.

The barrel has a press-fit ratchet wheel with a square hole on it, which I thought maybe wasn't pressed down enough, causing the top of the ratchet wheel to foul against the underside of the barrel bridge, but there is still a gap in there, so that's not it either.

I have no idea what's causing it.  I have attached some teardown photos as well as current photos.

Edited January 18, 2023 by GregG
Fix typo

[HectorLooi]

Try removing the barrel arbor from the barrel and fitting just that onto the plate and see if the barrel bridge can seat fully.

The hole closing punch can distort the plate and affect endshake.

[JohnR725]

Any time you're having a problem putting a bridge on its best to remove everything under the bridge and just try the bridge itself to make sure you not having a problem there. A lot of times the pins in the plate the steady pins are really tight you want to verify whether that's what's going on or whether there's something else going on.

10 hours ago, HectorLooi said:

The hole closing punch can distort the plate and affect endshake.

Then hole closing can seem simple and easy but you can end up with interesting issues. Like for instance of the hole was oval in shape and you close it, is now no longer centered.

[watchweasol]

Hi as mentioned any punching hole closing etc can and will distort the bridge if not done correctly. Also looking at the picture of the barrel the cap does not look to be seated squarely might just be the picture but worth a check.    Cheers

[GregG]

12 hours ago, HectorLooi said:

Try removing the barrel arbor from the barrel and fitting just that onto the plate and see if the barrel bridge can seat fully.

The hole closing punch can distort the plate and affect endshake.

Good call.  I tried fitting just the arbor, and it wouldn't budge, so it's not the barrel itself.  I continue to broach the hole open, and the plate fits on almost perfectly and the arbor is free to spin.  Though I did have to broach it quite a bit.  Sideshake is no longer as good as it was after initially staking, but better than it was before staking.  I reassembled the watch dry to make sure everything else is still good.  The watch is running, but with a low amplitude.  Unfortunately there are a few variables here.  Perhaps my staking/broaching job wasn't great, or there's another pivot that needs it, or the fact that it's dry, or the mainspring is tired.

2 hours ago, JohnR725 said:

Any time you're having a problem putting a bridge on its best to remove everything under the bridge and just try the bridge itself to make sure you not having a problem there. A lot of times the pins in the plate the steady pins are really tight you want to verify whether that's what's going on or whether there's something else going on.

Then hole closing can seem simple and easy but you can end up with interesting issues. Like for instance of the hole was oval in shape and you close it, is now no longer centered.

I will try fitting just the bridge when I have time.  Though this is perhaps the dozenth time I've done it and never had an issue such as this.  I've had it where the hole is simply too small, and broached it open a bit and it eventually fit like a glove, but I don't think I've ever distorted it badly.

44 minutes ago, watchweasol said:

Hi as mentioned any punching hole closing etc can and will distort the bridge if not done correctly. Also looking at the picture of the barrel the cap does not look to be seated squarely might just be the picture but worth a check.    Cheers

I think it's just that the front of the picture is in focus, but the back isn't.