Bent minute wheel

[gary17]

Het guys 

Just removed a minute wheel from a landeron chrono and the staff or pin or pinion (the metal stick that goes through the wheel) is bent on the end were it should sit in the jewel. I am just wondering the best way to straighten it. Can it be replaced (just the staff) or is it a complete new minute wheel if available? or is it possible to straitehen it?

If so how?

Thought its worth a ask before i start with the tweezers on it

cheers

gary

[Watchtime]

I would go for replacing it, it will probably break if you try to bent the pivot. if you want to try it, heat the pivot and carefully bent it.

[watchweasol]

Hi Gary can you post a picture of it,  If it too far bent its a replacement job.

[Tudor]

I'd get the replacement first, and then try to straighten, for the practice.

Older movements have harder pivots (generally speaking) than newer ones, so it is likely to break.

On the other hand, it DID bend to it's current position without breaking, so there is a glimmer of hope.

I'd probably rig it up on a staking set (since I have one now) and choose a stake and support hole (or stump) which lets you press the shaft in a very controlled manner. Perhaps even using a jeweling tool (or attachment) to avoid pressing it too far.

Heating with a soldering iron is a good idea, and once straight, I'd heat and quench it to try and increase the hardness again. That may or may not work. Dunk it in some oil once it's hot, and leave it there for five minutes or so.

[Nucejoe]

4 hours ago, Tudor said:

it DID bend to it's current position without breaking

I agree, it can be straightened, however, how do you ensure trueness of the arbour? 

 On a lathe which takes pretty advanced machine work I guess.

[Tudor]

Caliper? A lathe would be rather cumbersome I think.

[nickelsilver]

I straighten pivots in the lathe, not with it running, just holding the part and turning it by hand to see where to bend and when it is straight. I use heavy nickel tweezers, or sometimes Dumont #8 tweezers which are specifically for this. Most important is to heat the tweezers tips in an alcohol flame until they are almost too hot to hold, and bend a little, check, bend a little, check. Some pivots are too far bent to save, but if they are saveable the heated tweezers make a world of difference. The heat isn't enough to affect the temper of the steel, it does help it relax while bending though.

[Tudor]

So, I’m imagining a wheel with a long pivot. Do you grab the bent end in the collet?

[nickelsilver]

27 minutes ago, Tudor said:

So, I’m imagining a wheel with a long pivot. Do you grab the bent end in the collet?

No, the pivot sticking out. On a 4th wheel this will usually mean gripping on the pinion leaves; get it turning true, then coax the pivot straight with the hot tweezers. It's the same for any wheel, I do this on 5 ligne balances with 0.06mm pivots or pocket watch 4th wheel pivots that are 0.3mm.

[Tudor]

So, you just rotate the pinion by hand in the lathe, and "tweeze it out" with hot tweezers? Is that it?

[HSL]

I think I have a similar technique which I can show.

I have a slightly bent seconds wheel from a Landeron 48.

I hold the pivot firmly in some discarded tweezers.

Next, I apply heat on the tweezers, I use a torch but one can use an ethanol burner too.
Just make sure you apply the heat a bit away from the actual pivot.

When the tweezers are so hot you can’t hold them let go of the grip.

The pivot is now softer and can be worked on without breaking, just make sure it hasn’t a blue color since then it has become too hot.

Fasten it in your lathe, choose a chuck slightly bigger than the pivot diameter.

Since the pivot now is softer and not to hardened you can adjust the straightness by lightly tapping at it when you found its high point. One just rotates the lathe by hand until the pivot is above the index pin.

After you rotated it a couple of times by hand and lightly tapped on it will become straighter for every turn. And that is one way to do it.

 

[gary17]

Hey

Thanks everyone as usual great help. 

I used staking kit. Broke one but second one is in watch and working. 

Cheers

Gary