Saturday, September 8, 2012

Bumper Part 2 - the Rebuild

In the previous post on the Elgin 607 Bumper movement, I had taken apart a movement that I'd bought on Ebay.  It was sold as nonrunning, but was nice and complete.  In the interim, I ran the parts through my new (well, new to me!) cleaning machine, dried them, polished the jewels and pivots with pegwood and pithwood, and inspected all the parts.

Since I have acquired five 607 mainsprings in the course of buying mainspring lots, I thought I'd pop in a new one.  You can see the braking spring, a tiffer piece of spring that essentially grips the barrel wall, but allows the spring to slip to prevent overwinding.

This was kind of a pain, because you have to stop after winding most of the spring into the winder, then fold the braking spring under so it gets pulled into the winder, and unlike a spring with a barrel end hook or T-end, you want to wind the whole thing into the barrel.

Next, I reassembled the autowind module.

The trickiest part was remembering how this part went together.  That lone screw holds the pawl spring at one end, and there's a groove in the winding sector that the spring fits into.  The fingerprint on the bench block will give you some idea just how SMALL the parts are - the 3 screws holding the  winding sector hub together are about the size of balance cap jewel screws. 

Once that's put together, the ratchet pawl is added to the plate. (sorry about the focus)

Then the winding sector assembly is added.

Add the lower plate, and it's ready to go!

I won't show the assembly of the movement, which is really pretty straightforward, not to mention just like the disassembly only backwards.  I was pleased to note that the balance took right off when installed.  The next step is to add the bumpers.  This is a fiddly step, since the bumper block doesn't have separate screws.  The same screws that hold down the springs attach the bumper to the pillar plate.  And of course, the springs try to turn as you tighten the screws down!

With the bumpers in place, you just add the autowind module and tighten two screws.

Note the little black mark on the ratchet wheel.  I marked that so I could see if moving the winding weight worked to wind the watch.  As you can see in this picture, where it's moved about 90 degrees, it does!!

 Add the dial and hands, and we've got a newly cleaned Elgin 607 Bumper!  A nice little piece of American Watchmaking history!