On My Bench - Seiko 6139-6002 - The First Automatic Chronograph

Yes it's possible, but it would depend on the specific situation. For example there would have to be enough material surrounding the existing hole to enable a separate jewel to be installed, so if you look at the 7750 main plate above where I have added a bushing, I had to ream the hole large enough that there isn't a lot of material left to seat the bushing - jewel might be larger on the OD, and in that case it would be iffy trying to put a jewel there.

On the 861 that I have shown, the barrel bridge is often worn in this location, and on the new 3861 they have added jewels foe the barrel arbor in both the main plate, and the hour recorder bridge. To me this is a worthwhile upgrade, as I bush these very frequently (will be doing another one today). But it doesn't have to be a jewel - even putting a bushing in is a huge step up from just making a hole in the plate. I use bronze bushings, so they wear much better than the soft brass plate does, and if it already had a bushing this would be 30 seconds job to replace it, instead of me having to spend 15 minutes.

In this case there is no pure "performance" gain in that the watch won't run better with a jewels for the barrel arbor than it would with a new main plate with an unworn hole. The only time the barrel arbor moves in these holes are when you are manually winding the watch. In an automatic watch like the one Jim is working on, reducing friction here can assist the automatic winding in keeping the watch wound - most Seikos are very efficient anyway, so not sure it is a huge performance boost.

Jewels in other areas may improve the performance. With a lot of old American made pocket watches, they came in different grades with different jewel counts. If the jewel count was low, say a 15 jewels version, it would often require a much stronger mainspring than say a 23 jewel version, because there is more friction in the 15 jewel watch. So the brands would make mainspring of differing strengths that would be used for the different models. If you have more jewels it can reduce the torque required, allowing a weaker spring, and less pressure on all the working parts - this can mean better performance and longer life for those parts.

If I were designing the new Speedmaster movement, I would add jewels for the barrel arbor as they have done. I would then add jewels for the center wheel, so on in the main plate and one in the main bridge - these are currently just holes in the plate with no jewel or bushing. You could go on to add jewels in other places, but I don't think they would give you much benefit, and in some cases may cause problems.

Cheers, Al

Now have the train assembled and the chrono parts fitted and checked.
The donor pallet lever has been fitted and the balance dropped in and is ticking away nicely with one or two turns to wind it.



A quick look on the timegrapher shows much better readings than the first lot, which looked like this:



Now they look like this:



The pallet stones/escape wheel haven't been lubricated yet so I'll let that run for ten minutes or so for tracks get worn through the epilame, then I'll lubricate the pallet stones which should improve performance.

In the meantime, I'll finish the "Foggy Seamaster" for @bindo so that he can collect it tonight.

I'm feeling a bit tender today (hernia flare-up) so only doing some simple stuff.

The crown stem assembly on this model carries a spring loaded sliding pinion used to rotate the internal bezel. This one was original but it had some bad rusting that needed to be cleaned up, as well as the hardened stem seal to be replaced.



The parts were stripped and the stem seal chipped off.



Then some de-rusting and cleaning, a new lubricated seal, put back together and ready for another 50 years.



PS: Even though the pinion still has imperfect leaves (teeth), it will only be driving a plastic gear ring so a new one isn't really warranted.

Cold wet and windy day outside, good to be inside working on a watch.

But then..............I'm half way through installing the day/date mechanism and I hear:

"Hey Darl', my tea maker isn't heating up, can you take a look at it for me?"



So a couple of hours lost and the Breville BTM800XL is cactus.

Ah well, there's always tomorrow.

Setting the hands.

I have a couple of analog meters but the Fluke 87V I bought some years ago is a brilliant piece of kit. I do like an analog meter though - here are a couple used for the Hi-Fi:

The second one is a real oddity these days!

Cheers, Chris

Uh Oh.

I got so involved in getting things back together I forgot to take photos. It's been running nicely for a day and a half now, so a final pic to finish off.

Here's a better after shot. Hard to get everything in focus as you have to stop right down and I've lost the light as it's become rather overcast.

That’s gorgeous work.

Not the angle, the camera was straight on.

I'd say it's a combination of plastic and metal parts in a 48 year old watch not functioning as well as the day they left the factory.

But now that you've pointed it out my OCD has kicked in and I'll probably try to make it work like it did when it was new.

@JimInOz do you happen to have a timegrapher photo of the watch after fine tuning it?
😀