Reply To: Full bridge on American Pocket Watches

[Bob Tascione]

Hi Jay and welcome!

Oooops, I guess I’m not too popular around your house right now! I’ve also pulled all nighters working on watches without realizing how late (or early) it was.
I’m happy you’re having fun with the course though.

There are a few differences between the 3/4 and the full plate movements.
Letting down the mainspring is one. To let down the mainspring you’ll need either a let down key, bench key or the stem and crown from the watch. Any of these will work well. Remove the movement from the case and you should see a small hole along the edge next to the where the winding stem enters. Insert whatever you are using to let down the spring into the winding hole and turn it about half a click and then insert a small pin into the hole and push slightly. This will move the click away from the ratchet which is hidden from view by the plate. You can now release the power by allowing the let down key to turn slowly.
After all power is let down and hands and dial are removed you can proceed to disassemble the movement by removing the balance cock and balance first. When separating the plates view between them making sure that the pallet fork lifts freely with the back plate and doesn’t get jammed while lifting plate. This can bend or break the pallet fork pivot.

When reassembling the movement a neat trick is to build the movement “upside down”. I covered this in an earlier post which I’m pasting here for you.

The full plate watch can be a little tricky when it comes to assembly as compared with 3/4 plate and finger bridged movements. It can be tough getting the pallet fork situated during assembly. One tip on assembling them that works great for me is to assemble the movement “upside down”. There probably isn’t really an upside down so I guess I mean the opposite way that you would assemble a 3/4 plate. By placing the watch on the holder with the balance cock side down (leave the balance cock and balance off at this point) towards the bench surface I find it much easier to build the wheel train and install the pallet in place. You can then place the dial side plate on and line up the arbors by viewing between the plates. Just a tip but it does seem to work well for me

I hope this helps Jay. Please keep us posted and feel free to ask more questions anytime.

Bob