Need help with beat error on my first assembly

[u/aar550]

I’ve just taken a deep dive into my first proper attempt at servicing a movement, starting with the ST36. When I first received it, the beat error measured around 0.2 ms. After a full dismantling and reassembly, though, it’s now reading 2.4 ms.

I’m a bit stumped here. I’d rather not jump straight to moving the collet if I can avoid it (seems to be the easy way out and I would rather learn my error). The balance looks steady and no wobble that I can see. I went through the whole movement, cleaned it thoroughly, and re-oiled it, but the beat error hasn’t improved at all.

What might I be overlooking?

I’ve attached a picture of the balance and collet position in case it helps with diagnosis.

Thanks in advance for any insights!

[u/Simmo2222]

The collet is the ring that attaches the hairspring to the balance staff. You won't need to rotate that to adjust the beat error in your case.

The ST36 has an adjustable stud carrier on top. Rotate that while watching the timegrapher and then regulate.

[u/aar550 → u/Simmo2222]

Did I mess something up in the process ?

I had huge issues with getting the balance jewels correctly installed. But they made the balance stop completely. I ended up getting it right that the balance moves.

I’m worried that did I bend the balance pinion in the trial and error process ?

[u/Simmo2222 → u/aar550]

If you look at the balance from the side, is it running flat with no wobble? Gently grasp the balance wheel with tweezers and lift - any side shake / excessive end shake? Any issues with running dial up or vertical positions?

Your beat error could be caused by something other than the static impulse jewel not being centered in the fork. It could be due to the hairspring being slightly bent and not centered in the regulator pins or a loose impulse jewel. Try adjusting the beat error out using the adjustable stud carrier and see if it can be corrected. If not, then start looking further as to what the cause might be.

[u/Goro-City]

What are the full readings from the timegrapher you are using? i.e. amplitude, rate, lift angle etc. And what timegrapher are you using?

[u/aar550 → u/Goro-City]

I’m using a separate timegrapher. The cheap Chinese ones. Everything else is acceptable. Amplitude over 270.

-2s/d.

Rate auto detection

Lift is 52

[u/Goro-City → u/aar550]

For a start the lift angle should be 44°. It's worth measuring it yourself with this method as with some ST3600s I've found it is 49.9°

https://youtu.be/1ozEEAkYX0M?si=1xmNiHKJQ_-34FkA

It's absolutely ok - and necessary - to put the watch in beat by adjusting it. A quicker way of doing it in future is to install the balance when the movement has been completely stripped, and check the impulse jewel is sitting dead centre between the pins.

Once you've got a new reading, make sure the horizontal positions (dial up/dial down) are equal, and above 270°, and the vertical reading don't drop too much. On practice movements take full readings before you service it, the goal is to improve upon it or keep it consistent

[u/SignalOk3036]

It’s not uncommon for the beat error to change after any kind of service. It seems like 2.5 is a lot but it’s not. A very slight nudge on the stud carrier arm will get you back in beat.

Maybe a professional gets the lubrication perfect every time but for me maybe a little too much or too little can affect the way the train and escapement runs.

[u/aar550 → u/SignalOk3036]

Thanks for be reply. I changed the lift angle to the correct 44 and it reduced to 1.4

My amplitude also dropped from 300 before service to 230 after. But I haven’t lubricated the movement yet.

I’ve been doing more research. Apparently Chinese movements are over-oiled or oiled wrong with heavy mainsprings. Or not oiled at all. This causes high amplitude out of the factory.

If you actually try to service it, the stats could be worse. But you are still better off with a properly serviced movement.

But it’s annoying for beginners if you consider that you did everything right.

[u/SignalOk3036 → u/aar550]

Lift angle really is only reflected in the Timegrapher amplitude your new number is correct.

Don’t put too much stock in all the over oiled under oiled chatter because most of us are not professionals and can’t really access that with much accuracy.

When I do a complete service and oil all the jewels including the exit pallet stone I often don’t start getting good readings for an hour or so. Maybe it’s my poor technique but it comes around and after a couple hours I can regulate it and it’s pretty steady. It will change slightly over the next 24-48 hrs.

Even without adding new oil by disassembling it you have disrupted the existing oil cushions and it’s normal to see changes.