NEED HELP 1914 chronograph mono pusher piece fell out

Harry jenkins · May 25, 2025

I am not a watch maker. Far from it. This watch came into my possession. Was working fine.

Running great keeping good time for a watch from 1914. Been in drawer for few months.

Today I wound it a little, pushed the single pusher, nothing happened. I wound it more because in the past I've noticed that the chronograph dries the power quicker than not engaging it at all. Pushed the chrono pusher. Nothing still. Full wind. Pushed chrono pusher - still nothing. Opened case back. Thought I heard something fall on the ground. Looked on ground - found this:

Here is a picture of the movement when I purchased it.

Here is a picture of the movement now.

Here is where the fallen part belongs. (I hope there are no more fallen parts)

I am asking - how screwed am I? Can I put it back myself? (it has touched human flesh) What damage has been done? Why do you think it fell out?
Many thanks in advance.

ErichKeane · May 25, 2025

That part is the 'wheel over fourth wheel' for other Chrono movement (not sure on that movement, it is old enough to not be the chrono movements I'm familiar with). It is an intermediate chronograph wheel.

It fits via friction-fit on that post of the pinion.

You COULD likely/gently place it back. It is only friction/push fit onto that post, and that is how the manuals show to install it (again, for the Landeron movements I'm familiar with, but it looks identical).

IF I WAS YOU: I'd clean it. Use a brush and some IPA or Bestine, and clean it off best you an, then don't touch it. Use gloves/fingercots/etc. Then, using level even pressure, push it down until it 'stops' under a small/reasonable amount of pressure. Also, make sure it is meshing well with the wheel next to it.

THAT SAID, it is entirely possible that it is just worn out enough to not keep itself there anymore. It should be friction fit, so if it isn't anymore, it is a problem. If it seems like it isn't going to keep itself on via friction, I'd go to a watchmaker.

AS to why it fell out:
1 of 2 things:
1- Previous watch maker didn't push it firmly enough. It is the 'last' piece during reassembly, so he perhaps didn't notice.
2- It is just worn out over all these years, either it or the pivot it presses onto. It could perhaps be 'staked' to be tighter, but that is another thing that will require a watchmaker to service.

Harry jenkins · May 26, 2025

ErichKeane
That part is the 'wheel over fourth wheel' for other Chrono movement (not sure on that movement, it is old enough to not be the chrono movements I'm familiar with). It is an intermediate chronograph wheel.

It fits via friction-fit on that post of the pinion.

You COULD likely/gently place it back. It is only friction/push fit onto that post, and that is how the manuals show to install it (again, for the Landeron movements I'm familiar with, but it looks identical).

IF I WAS YOU: I'd clean it. Use a brush and some IPA or Bestine, and clean it off best you an, then don't touch it. Use gloves/fingercots/etc. Then, using level even pressure, push it down until it 'stops' under a small/reasonable amount of pressure. Also, make sure it is meshing well with the wheel next to it.

THAT SAID, it is entirely possible that it is just worn out enough to not keep itself there anymore. It should be friction fit, so if it isn't anymore, it is a problem. If it seems like it isn't going to keep itself on via friction, I'd go to a watchmaker.

AS to why it fell out:
1 of 2 things:
1- Previous watch maker didn't push it firmly enough. It is the 'last' piece during reassembly, so he perhaps didn't notice.
2- It is just worn out over all these years, either it or the pivot it presses onto. It could perhaps be 'staked' to be tighter, but that is another thing that will require a watchmaker to service.

Thank you so much this reply. I will try and report back.

Archer · May 26, 2025

ErichKeane
That part is the 'wheel over fourth wheel' for other Chrono movement (not sure on that movement, it is old enough to not be the chrono movements I'm familiar with). It is an intermediate chronograph wheel.

It fits via friction-fit on that post of the pinion.

You COULD likely/gently place it back. It is only friction/push fit onto that post, and that is how the manuals show to install it (again, for the Landeron movements I'm familiar with, but it looks identical).

IF I WAS YOU: I'd clean it. Use a brush and some IPA or Bestine, and clean it off best you an, then don't touch it. Use gloves/fingercots/etc. Then, using level even pressure, push it down until it 'stops' under a small/reasonable amount of pressure. Also, make sure it is meshing well with the wheel next to it.

THAT SAID, it is entirely possible that it is just worn out enough to not keep itself there anymore. It should be friction fit, so if it isn't anymore, it is a problem. If it seems like it isn't going to keep itself on via friction, I'd go to a watchmaker.

AS to why it fell out:
1 of 2 things:
1- Previous watch maker didn't push it firmly enough. It is the 'last' piece during reassembly, so he perhaps didn't notice.
2- It is just worn out over all these years, either it or the pivot it presses onto. It could perhaps be 'staked' to be tighter, but that is another thing that will require a watchmaker to service.

May also be called a chronograph drive wheel…it is the wheel the takes the power from the base movement and starts the transfer to the chronograph.

This is a press fitted wheel, so it is pressed with some force onto the fourth wheel extended pivot. Typically most watchmakers would use a staking set or jewelling tool to press this in place. Personally I use the Horia tool for this operation, because it allows me to give some support on the dial side of the movement.

The pressing on of this wheel needs to be done carefully. You can damage the wheel, break the pivot, push the dial side jewellery out of adjustment, damage teeth on it and the wheel it meshes with…and the wheel needs to be pressed on to the correct height, so that top of that wheel is at the same level as the wheel in the coupling clutch/yoke.

Also if the wheel was presumably pressed on to the correct height and fell off, then as you say the hole in the wheel needs to be tightened.

So although it seems like a simple thing it isn’t a DIY job in my view, unless the OP is prepared to pay even more to fix it if something gets damaged.

My $.02…

Harry jenkins · May 26, 2025

Archer
May also be called a chronograph drive wheel…it is the wheel the takes the power from the base movement and starts the transfer to the chronograph.

This is a press fitted wheel, so it is pressed with some force onto the fourth wheel extended pivot. Typically most watchmakers would use a staking set or jewelling tool to press this in place. Personally I use the Horia tool for this operation, because it allows me to give some support on the dial side of the movement.

The pressing on of this wheel needs to be done carefully. You can damage the wheel, break the pivot, push the dial side jewellery out of adjustment, damage teeth on it and the wheel it meshes with…and the wheel needs to be pressed on to the correct height, so that top of that wheel is at the same level as the wheel in the coupling clutch/yoke.

Also if the wheel was presumably pressed on to the correct height and fell off, then as you say the hole in the wheel needs to be tightened.

So although it seems like a simple thing it isn’t a DIY job in my view, unless the OP is prepared to pay even more to fix it if something gets damaged.

My $.02…

Thanks also for this - I haven't touched it yet. It's probably a good idea if I don't. I'm just not qualified. You say "Also if the wheel was presumably pressed on to the correct height and fell off, then as you say the hole in the wheel needs to be tightened." - I'm curious - how would one tighten a hole like that?

Harry jenkins · May 26, 2025

ErichKeane · May 26, 2025

Archer
May also be called a chronograph drive wheel…it is the wheel the takes the power from the base movement and starts the transfer to the chronograph.

This is a press fitted wheel, so it is pressed with some force onto the fourth wheel extended pivot. Typically most watchmakers would use a staking set or jewelling tool to press this in place. Personally I use the Horia tool for this operation, because it allows me to give some support on the dial side of the movement.

The pressing on of this wheel needs to be done carefully. You can damage the wheel, break the pivot, push the dial side jewellery out of adjustment, damage teeth on it and the wheel it meshes with…and the wheel needs to be pressed on to the correct height, so that top of that wheel is at the same level as the wheel in the coupling clutch/yoke.

Also if the wheel was presumably pressed on to the correct height and fell off, then as you say the hole in the wheel needs to be tightened.

So although it seems like a simple thing it isn’t a DIY job in my view, unless the OP is prepared to pay even more to fix it if something gets damaged.

My $.02…

Thanks so much for the response! I was only able to answer as I've been studying old books on a Landeron 48 and recognized the part! Books I've used so far have suggested much less accurate tools (tweezers, handset tools, etc).

So thank you very much for the correction/education! It is greatly appreciated. Id not realized it took so much force!

Foo2rama · May 26, 2025

Harry jenkins
Thanks also for this - I haven't touched it yet. It's probably a good idea if I don't. I'm just not qualified. You say "Also if the wheel was presumably pressed on to the correct height and fell off, then as you say the hole in the wheel needs to be tightened." - I'm curious - how would one tighten a hole like that?

You use a professional watchmaker with the tools to fill it in. Archer is an example of a watchmaker that can do that.

TIMElyBehaviour · May 26, 2025

Yep, I totally agree with our man Archer. It looks simple enough yeah, just put it on and press.

As archer said, you can snap the top of the pivot, bend the wheels when they get close and touch each other if they aren’t meshed correctly and you can also bend the pivot you are putting the wheel on to. And if you do you need to pull more parts off, find a replaced wheel and do a full service. This is a skill developed over time not something you can just press on.

Dan S · May 26, 2025

Harry jenkins
I'm curious - how would one tighten a hole like that?

Fine adjustments can probably be made with a staking set (precision punches and concentric holder), as long as the parts aren't too badly messed up. If you google, you can find some good videos.

Archer · May 26, 2025

Dan S
Fine adjustments can probably be made with a staking set (precision punches and concentric holder), as long as the parts aren't too badly messed up. If you google, you can find some good videos.

The good thing here is that the hole should still be round. When there is wear that makes a hole oval, it gets complicated because you need to maintain the original centre of the hole, so using a punch to close up a hole that is worn oval isn’t always a good idea. There you would bore it out and install a bushing.

In this case you might be able to close the hole up enough (probably not much required) and not throw anything off centre if you are very careful about it.

ExpiredWatchdog · May 27, 2025

Maybe it's just the picture quality but my eye say's someone's already tried closing it once (or more).

Harry jenkins · May 28, 2025

ExpiredWatchdog
Maybe it's just the picture quality but my eye say's someone's already tried closing it once (or more).

Based on the picture quality - I feared the same thing. Could be pixels but it looks a little off. I don't think finding a replacement piece for this would be easy given its age. All the info I could get was that it was a 'Top Quality gilt Lepine design' and that it is a very old L.Leroy & Cie Sterling Silver “Monopoussoir” Chronograph Wristwatch.

Harry jenkins · May 28, 2025

Archer
The good thing here is that the hole should still be round. When there is wear that makes a hole oval, it gets complicated because you need to maintain the original centre of the hole, so using a punch to close up a hole that is worn oval isn’t always a good idea. There you would bore it out and install a bushing.

In this case you might be able to close the hole up enough (probably not much required) and not throw anything off centre if you are very careful about it.

This sounds like a microscope job.

Harry jenkins · May 29, 2025

Hello - just to update you and incase it is of interest or useful to anyone in the future - I managed to get a statement from the master Swiss watchmaker who serviced the watch before it was sold - he said the following:

"There are various reasons why the wheel could have fallen off. This could be due to temperature differences (brass expands and retracts up to 10% more than for example type 304 stainless steel) and/or vibrations such as caused by handclapping or finger tapping, etc.

You (or a local watchmaker) can simply put the wheel back on. Here is how to proceed: degrease the axle a bit and clean the wheel with some benzine, then carefully chase it back on with a small boxwood dowel. Give it two or three gentle taps with a little watchmaker’s hammer so that it is level. Additionally, to avoid this from happening again, you could add a tiny drop of Loctite 243 (a thread-locker) on the axle before chasing the wheel back on."

This doesn't address any possibility that the wheel hole is damaged or that an attempt might have been made to make the hole smaller in the past - which it might have done. Hard to see without a microscope.

Archer · May 29, 2025

Harry jenkins
This could be due to temperature differences (brass expands and retracts up to 10% more than for example type 304 stainless steel) and/or vibrations such as caused by handclapping or finger tapping, etc.

This is absolute nonsense. The wheel was just too loose and he didn't bother to correct it.

ErichKeane · May 29, 2025

Harry jenkins
Hello - just to update you and incase it is of interest or useful to anyone in the future - I managed to get a statement from the master Swiss watchmaker who serviced the watch before it was sold - he said the following:

"There are various reasons why the wheel could have fallen off. This could be due to temperature differences (brass expands and retracts up to 10% more than for example type 304 stainless steel) and/or vibrations such as caused by handclapping or finger tapping, etc.

You (or a local watchmaker) can simply put the wheel back on. Here is how to proceed: degrease the axle a bit and clean the wheel with some benzine, then carefully chase it back on with a small boxwood dowel. Give it two or three gentle taps with a little watchmaker’s hammer so that it is level. Additionally, to avoid this from happening again, you could add a tiny drop of Loctite 243 (a thread-locker) on the axle before chasing the wheel back on."

This doesn't address any possibility that the wheel hole is damaged or that an attempt might have been made to make the hole smaller in the past - which it might have done. Hard to see without a microscope.

Archer can judge this separately and more authoritatively, but there is a LOT of very questionable stuff there. PLEASE do not follow that advise.

First re coefficient of thermal expansion. YES, the difference is actually quite a bit more than 10%, but at the scales we are talking about, so minimal that it doesn't matter. For something that is 0.5 mm in diameter, a 0C to 100C change in is about a 0.0005mm difference at most. That said, 304 stainless has a coefficent of thermal expansion ~16-18 according to all sheets I can find, and most brasses are within 15-20, so MAYBE at worst 10%, but in the end, VERY little.

Even so, that number pales in comparison to what a press-fit should be there. So I don't think at these dimensions that temperature change could matter enough to make this happen. Additionally, if vibrations caused it to fall off from 'handclapping or finger tapping', then no chronograph in the world would work. Wheels would be falling off willy nilly.

This definitely seems like he didn't notice that the wheel was too loose and is trying to blame something else.

As far as how to repair: GOOD GOD DO NOT USE 243 ON THE PIVOT. That is what is traditionally called blue loctite. Whoever services the watch the next time will break the pivot trying to remove that next time.

FIRST, that is a thread-locker, which requires a quite few thousanths of an inch clearance, so a proper press-fit should NEVER benefit from thread locker. Second, there are actually 'slip-fit' loctites that would be used in situations like this (some in the 600 series). Third, it is way too strong for this situation.

The cleaning of the pivot and pressing it back on are how you should do it, but as Archer mentioned earlier, you should use a tool that ensures pushing it 'squarely'.

EDIT TO ADD: I see that @Archer posted while I was typing this up, and much more succinctly 😀

Jan Dietrich · Jun 2, 2025

A Master watchmaker also once tried to convince me that it is a good idea do put a chronograph hand on with some superglue. I sometimes have the feeling that they can just say everything because everybody believes them. Achers advise in this forum is really good and professional in my opinion.

ErichKeane · Jun 2, 2025

Jan Dietrich
A Master watchmaker also once tried to convince me that it is a good idea do put a chronograph hand on with some superglue. I sometimes have the feeling that they can just say everything because everybody believes them. Achers advise in this forum is really good and professional in my opinion.

Methinks we're throwing this master term around all willy-nilly.

Harry jenkins · Jun 2, 2025

'Master'