With care

Back to Steve's Waltham 0s.

I'm usually pretty careful in any of my horological work but given that this is an heirloom of a friend... I took every precaution.

When removing the hands it is very easy to accidentally scratch the dial. In this case I have a special protector just for the job on a dial this small.

Missing crystal would be attached to an inner bezel.

It is popped off by inserting a wedge into a tiny slot on the side of the bezel. See the slot? Just slightly obscured by a couple clumps of dirt.

And I have a tool for that.

And there's the bezel removed. 

Flipping the watch over and loosening a couple screws and the movement slides out of the case nicely. It's sitting on watch paper to protect the dial on the other side.

Speaking of the dial, it is removed next.

Most dials are attached to the movement with 3 pillars. The movement has 3 tiny screws around its edge that anchor each pillar. Unscrewing them just a few turns releases the grip on the pillar.

Here's one of those screws and my matching screwdriver tip next to it.

And the dial now released from the movement. See the three pillars and the matching holes on the plate?

Note the beautifully enameled back of the dial. Quality.

And see the serial numbers on the plate there? A little jumbled looking, they're sometimes stamped by hand on the inside plates and other parts of the watch and, not unusually, often just the last several digits stamped on non-visible parts. You can see the full serial number is on the barrel bridge in the earlier movement photo as that part would be quickly visible to any owner who cared to look. 

The numbers match which strongly indicates that the movement is likely all original. Nice.

Next up I'll be removing the gear train on the back there. 

The black gears are for both setting the time and winding the watch. The gilded wheels are the motion works which drive the minute and hour hands.

After removing the hour wheel (the center golden wheel) underneath we find a familiar face, the cannon pinion.

It's the black nubby thing sticking up in the middle of the movement. 

And it is really small.

The rest of the wheels and gears on this side are easily removed.

Flipping the movement over it is time to take apart the time train.

I'll speed things up a bit and jump a couple moves ahead.

A quick reminder of the basic structure of the vast majority of mechanical watches.

Now compare to our movement below...

My finger is sitting on the mainspring barrel which has the first wheel (gear) on top of it.

Then there's the second (center) wheel, third, fourth and fifth AKA the escape wheel with teeth that look like little boots.

Lastly is the pallet covered by the balance wheel which has the screw heads circling it.

I've taken off the mainspring bridge and now the wheel bridge (with the corrosion on it) to show this.

That entire collection of 5 wheels is called the time train. In effect they transmit power starting from the mainspring down the wheel train to the escape wheel, pallet and balance wheel. 

Those last three parts (escape wheel, pallet and balance wheel) constitute the escapement and control the time keeping of the watch. They also make the tick tock sound you hear in most any mechanical timepiece.

Clear? 

Well I hope so.

Moving ahead... in the photo below the time train is now removed and the barrel and first wheel are sitting on the edge of the plate. 

The balance is next to come out. 

The balance includes the gold bridge (called a "cock") with the etchings on it and the large balance wheel it's connected to. The cock holds the wheel precisely in place.

Horology trivia... when a plate that holds watch pieces in place has two or more retaining screws it is called a "bridge".

When a plate is held with only one screw, like the one for the balance wheel, it is called a "cock."

The balance is a very delicate item and must be handled with great care.

Here it is removed and gently turned upside down exposing the extremely delicate hairspring. Dealing with hairsprings is a long story. Perhaps for another time.

Note the portion of serial number on the underside of the cock. 

And (here's one new to me)... The last three digits also appear to be hand printed on the underside of the balance wheel arm in white letters. Wow.

I used my digital microscope to get a close up of the stamped numbers and to check the condition of the screws and the hairspring on the balance wheel. 

Everything seems pretty shipshape.

Horology history...

Mechanical timekeeping is hard. Many different things can affect the accuracy of a mechanical movement.

One such thing is temperature. Especially for watches.

Summarily, in the very old days, watches would run faster when they were cold and slower when warm.

Why? For several reason but one major reason is that the metal in the balance wheel would expand and contract changing the size of the arc and length of the spin of the wheel.

Look closely at our balance wheel itself. The band with the screws in it. 

It has two features I'll call out. Note that the circular band is made of two different layers of metals. Brass and steel.

Note also that there is a gap in the band. It is not a complete circle of metal. There's actually two gaps. You can see one of them below (or both in the image above).

Long story short the use of brass and steel layers in the wheel band and gaps in the wheel are designs that allows the different metals to expand and contract at different temperatures in a controlled manner and the net effect is to counteract the impact of changing temperature on the balance wheel. 

Summarily these changes help maintain more consistent performance of the balance wheel and thus more consistent timekeeping.

The details are complex and fascinating (for those who care to understand more) but I won't go into them all now.

Back to our story...

Last item to remove, and had been hiding under the balance, is the pallet. 

The pallet is essentially a fancy lever.

Removed here and viewed under my new digital microscope.

The wedge shaped purple stones are the pallet jewels that mesh with the escape wheel. The fork on top meshes with the balance wheel. Yes mm scale on the right.

The pallet is a bit dirty as the magnification of the scope makes plain but overall the jewels and the rest of it look to be in very good shape.

And since we're playing with the scope...

Here's the cannon pinion.

Incredible, ain't it!

Coming up...

Part 2 of the disassembly. 

Yeah there's a lot left.