Loose pinion

[dnhb]

I have a Waltham key-wound pocket watch, small seconds: 20640806 on base plate & 640 80 6 on top plate. The pinion shown in the photo of the rear of the top plate - driven by the barrel - is loose & doesn't turn the main (first ?) wheel on the same arbour. The other photo shows the arbour on the dial side which appears to have a clip of some sort around it. I'd be grateful for advice as to how to proceed to rectify this problem.

[mbwatch]

Remove the cannon pinion from the dial side first. The "clip" you describe is sort of a metal tab some American companies designed their cannon pinions with in order to make it easier to tighten friction. If that is the problem, the solution is as simple as gently squeezing the tab with tweezers to bend it ever so slightly inward, while supporting the inside of the cannon pinion if possible (it may be harder to support inside since it does not have an open tip as a hollow tube)

The cannon pinion should just pull straight off of the arbor on the dial side if you pull it straight up with tweezers. There's no jewel in danger of breaking and the arbor is thick so there isn't much risk of breaking the arbor.

But when you are describing that the center wheel's pinion is not turning the arbor, is the pinion firmly attached to the center wheel? If you remove the center wheel and hold onto the rim of the wheel, does the pinion turn independently of the rest of the wheel? It should not. 

I'm not sure if this was the case on older Waltham, but the pinion may be threaded onto the center wheel arbor and they are often loose. This was a safety mechanism for a broken mainspring and may just need to be tightened back down. I can't remember for sure, but these might be a reverse (left) thread instead of normal right.

And does the entire arbor turn independently of the wheel? Also should not.

Edited Wednesday at 01:01 PM by mbwatch

[dnhb]

3 hours ago, mbwatch said:

Remove the cannon pinion from the dial side first. The "clip" you describe is sort of a metal tab some American companies designed their cannon pinions with in order to make it easier to tighten friction. If that is the problem, the solution is as simple as gently squeezing the tab with tweezers to bend it ever so slightly inward, while supporting the inside of the cannon pinion if possible (it may be harder to support inside since it does not have an open tip as a hollow tube)

The cannon pinion should just pull straight off of the arbor on the dial side if you pull it straight up with tweezers. There's no jewel in danger of breaking and the arbor is thick so there isn't much risk of breaking the arbor.

But when you are describing that the center wheel's pinion is not turning the arbor, is the pinion firmly attached to the center wheel? If you remove the center wheel and hold onto the rim of the wheel, does the pinion turn independently of the rest of the wheel? It should not. 

I'm not sure if this was the case on older Waltham, but the pinion may be threaded onto the center wheel arbor and they are often loose. This was a safety mechanism for a broken mainspring and may just need to be tightened back down. I can't remember for sure, but these might be a reverse (left) thread instead of normal right.

And does the entire arbor turn independently of the wheel? Also should not.

Thanks for the prompt response. I apologise for not stating the issue more clearly. The problem is that - what I now know I should have called - the centre wheel is not being turned by the pinion (which is driven by the barrel) with which it shares the arbour (1st photo above). The pinion & arbour are indeed reverse threaded but the arbour (the 'screw') is clearly damaged ('rounded' rather than 'sharp' threads) with swarf evident. When the pinion is screwed on there is only enough connection to prevent the pinion being lifted off but not enough to stop it turning on the arbour. Is a (reversible) repair (threadlocker?) possible in the short term while a replacement centre wheel assembly is sought so that the viability otherwise of the watch can be established?

[mbwatch]

2 hours ago, dnhb said:

Is a (reversible) repair (threadlocker?) possible

Yes I think blue thread locker would help you out here. You will lose the safety mechanism if the mainspring snaps, which risks damage to train wheel teeth. But your watch might run.

You can maybe try inserting a hair inside the pinion and threading it on. That might give it just enough to grab hold without thread locker. Or a tiny piece of superfine copper wire, a strand from some stranded electronics wire.

[dnhb]

On 5/14/2025 at 8:51 PM, mbwatch said:

Yes I think blue thread locker would help you out here. You will lose the safety mechanism if the mainspring snaps, which risks damage to train wheel teeth. But your watch might run.

You can maybe try inserting a hair inside the pinion and threading it on. That might give it just enough to grab hold without thread locker. Or a tiny piece of superfine copper wire, a strand from some stranded electronics wire.

I've gone the threadlocker route having tried the material insert approach without success. The watch runs but I'm chary about winding it more than a turn or so in case the 'repair' gives way; still, there's an element of satisfaction in getting it going at all as it's a single bridge/plate design which I could only assemble dial side up & then flip over in order to be able to insert the 3 securing screws. The reassembly took a number of attempts over many hours but at least I got considerable manipulation practice & the experience will come in useful in future. I'm now faced with my ignorance about how to manually set the the time as this key-wound Waltham pocket watch doesn't have the usual pull-out stem facility. All I can think of doing is to adjust the regulator arm until it catches up with the current time & then revert to the central position.....

[mbwatch]

Use probably the same key as you wound it with - on the end of the cannon pinion is a square that the minute hand is mounted to. You just need to turn the square, which will overcome the cannon pinion's friction and set the hands.

That said, this could be the reason your wheel and pinion were separated and thread damaged. If the cannon pinion had been rusted or seized on and it was turned, it could have damaged the connection between the pinion and wheel. If it felt like your cannon pinion could turn on the center wheel arbor before and there is some grease under it, this should not be a problem.

[dnhb]

1 hour ago, mbwatch said:

Use probably the same key as you wound it with - on the end of the cannon pinion is a square that the minute hand is mounted to. You just need to turn the square, which will overcome the cannon pinion's friction and set the hands.

That said, this could be the reason your wheel and pinion were separated and thread damaged. If the cannon pinion had been rusted or seized on and it was turned, it could have damaged the connection between the pinion and wheel. If it felt like your cannon pinion could turn on the center wheel arbor before and there is some grease under it, this should not be a problem.

Thank you. I did wonder if that was the solution but at present there isn't any of the cannon pinion square above the minute hand so obviously I haven't seated the hands far enough down. But if I address this I'd be concerned that the connection I've achieved between pinion & centre wheel arbour would be broken & the watch would no longer run. Maybe that's one of drawbacks - along with vulnerability to spring failure - of the type of repair I've effected. But please don't think I'm not grateful for the education you've provided f.o.c.....