Service and Reassembly: Patek Philippe Calatrava calibre 12”’-120 (1943)

It’s been quite a while since I took apart John’s Patek Philippe Calatrava, and much time was spent polishing components. Finally, the time has come to put the movement back together. Exciting times, and I can’t wait to see the movement in its full glory! As usual, I start off with a new mainspring. I had to guess a bit here, as somebody had shortened the mainspring – so I didn’t know what size should be in there.

With the new mainspring in the barrel, let’s look at some polishing work.

I did a couple of trial runs with screws from other watches that needed a bit of cleaning up, just to get the technique right.

When using diamantine, I never got a satisfactory finish, even with the extra fine grade, a clean glass surface, and lots of mushing it into a paste with oil. There were always some scratches left (only visible through a loupe), and I just wasn’t satisfied. This is a Patek Philippe, and I wanted to to the job right.

So after trials with leather, wood, and other unmentionable substances, I finally resorted to the fine range of lapping films 3M supplies. Starting with a 9 micron grade, I moved down to 3 micron, and then 0.3 micron for the final polish. This gave me the best results by far, so let’s see some photos of that.

This is one of the case screws, and even with the naked eye, you can see that the slot has been damaged, and that the polish is damaged.

As it’s badly damaged, I start off with a 1400 abrasive paper. I just take off enough to create an even surface. The screw already looks a lot better, but with a rough surface.

Next, I use a 2000 abrasive paper. To the naked eye, this already looks pretty good – almost mirror polish. Under the microscope, not so much.

Now I start with the 3M lapping films. Above, the screw head after the 9 micron film.

After the 3 micron film, we are nearing perfection.

After the 0.3 micron film, I have a result that I am happy with. Very happy.

So, now for polishing over 20 screw heads, and all sorts of other components. Swan neck, regulator, clutch lever, …. This takes me over 10 hours (not counting the 6 hours of trials I did).

The balance cock reassembled after polishing its components. There are some spots on the side of the swan neck and inside the regulator, but I have to consider the trade-off between shine and preserving the anglage. A simple choice for me. This is conservation work, and I can’t do anything that takes away something existing, so I stick to polishing the straight surfaces with minimal material removal. This leaves room for a maitre polisseur to go completely mental on this movement in 20 years time, and still be able to completely restore it. For the time being, I’m very happy with the finishes I’m getting.

That’s what the balance cock looked like before. You can also see the damaged screw heads.

Slowly but surely, I put the movement back together. I notice that whoever took it apart the last time mixed up the screws. I photographed all the screws with their components when taking the watch apart, and it just wasn’t right. Easy to figure out – they all are level with the other side of the plate when they are in the right position, and the heads fit properly. Just takes a bit of trying.

I oil as I go along, and polish some components I hadn’t thought about yet as well, like some of the smaller screw heads that had escaped first inspection. This is all worthwhile, because this is what a Patek Philippe movement should look like.

Even though nobody in the next couple of years will see the bottom plate, I give it exactly the same love and attention. I swap the jewel caps back to how I believe they were originally.

When I first try to adjust the beat rate, the movement is still over 20 seconds fast with the regulator in maximum slow position. I’m stumped, and decide to put the movement to the side until the next day. With problems like that, it’s always best not to do anything straight away, but to think first. In the evening, when telling John about the problem, I already have a hunch. The regulator probably grips the hairspring too tightly, thus only moving the hairspring around rather than changing its effective length.

As I have a training day with George anyway, I take the movement along, and he agrees. So I take a tiny bit of tension off the regulator, and, voila, I can adjust the beat rate properly. Who knows what I would have attempted yesterday, but probably not the right thing!

Now this makes me happy – straight line, good amplitude, good beat error, beat rate adjusted.

Now the case gets a good clean. I had the dent at 12:30 taken out by a case and glass specialist – thanks Richard from Watch Glass Cutting UK Ltd – not only did he do an excellent job, but he also did it very quickly!

Can you guess where the dent was? Super job!

Very strange marks on the case – VVII or WII, and I have the same on the bezel:

This can’t have happened at Patek Philippe, but must have been done later. Maybe somebody separated the case from the bezel and wanted to make sure they got reunited correctly – but how many Calatrava cases do you have in your workshop at one time???

And I can finally put the movement back into its case.

The hour hand was damaged. I can only guess how – looks like somebody pushing on the hand with a pair of tweezers. Or a crowbar… Stuff like this always makes me wonder. How can you do that? And why? A hand setting tool doesn’t cost that much money.

This leaves me with a bit of a conundrum. I want to get rid of the worst of the damage, but, as this isn’t pure gold, but probably 9ct. or so, I will get a discoloration when taking off any material. This will fade away with time, and I decide to ever so carefully remove some of the damage with a 3 micron and then 0.3 micron lapping film.

A slightly epic task comes to a very happy ending, and I’m pleased with my work if I may say so myself.

A very special thanks to my tutor George for all his help and encouragement!


9 thoughts on “Service and Reassembly: Patek Philippe Calatrava calibre 12”’-120 (1943)

  1. I’m the new owner of a Patek Philippe wrist watch serial number 75,776. It was my father’s, he is a watchmaker. 95 years old now. I have been reading about how Patek won’t supply parts to individuals and I was wondering if you might have an answer for me. This watch was in a box of junk that Dad bought many years ago when he bought out an old watchmakers workshop. It’s in good shape but it’s missing the crown and stem. Do you know where I could obtain these parts? Thanks for the help Ray Erbe

  2. General question: how much does it cost to service a vintage Calatrava? Assume that it is about 20 years old, no major parts needs replacement. I know that the estimate varies widely. Just an idea would be helpful.

  3. The case marks were made by Patek as they would have a lot of these cases lying about and these ensure that the carefully matched and tested case parts don’t get mixed up in the assembly or in subsequent servicing. This is normal practice by casemakers though I’m quite sure that Patek’s processes wouldn’t allow this sort of error regardless of markings.

  4. I am enthralled and very excited to experience you web site ,keep up the fabulous work many thanks. Barrie
    (I am one of George’s trainees he gave me your web address)

  5. Pingback: Patek Philippe Calatrava Part II

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