Bent forth wheel pivot - what do you do?

[Stian]

Hi guys, 

I working on a watch with small seconds, and the extended pivot on the fourth wheel is a bit bent. I would assess it to be maybe 3 or 4 degrees bent. This is enough for the seconds hand to rotate on a tilted plane, and the dial had been marked by it. 

Do you try to straighten the pivot, and if so, how? 

--

Thanks, 

Stian 

[StuartBaker104]

I would first try to see if you can get a replacement. Do you know what the movement is or can you post pictures?

Sometimes you will get away with straightening and sometimes they will break.

[Stian]

Hi Stuart, 

Thanks, I should have specified that this is a vintage watch and finding a new arbor would be very difficult. 

Would you have any guidance on when you would expect it to break and when you would think you can straighten it? E.g would it depend on the angle, the method etc? 

Stian 

[StuartBaker104]

Hi Stian,

It is more likely to break if you can't find a replacement :-)

On older watches, the hardness of these parts is somewhat unpredictable. Seitz makes a special tool for straightening pivots, but they are expensive even second hand.  This would give you more control, but wouldn't help with certainty.

If it is only a few degrees you may get away with it. Do you have a staking set with hollow punches?

If you post some pictures we may be able to help identify the movement. Key features are usually the keyless works parts and the diameter, but also good to see the bridges and any markings

 

[jdrichard]

I had the same problem and was successful in straightening it out. I used a pair of pliers and carefully worked it. Then I used my Jacot tool to smooth out any scratches I made with the pliers. As mentioned by others, the pivot could break if you are not careful and even if you are. However, you really have no choice other than getting a new wheel and shaft.

Sent from my GT-N5110 using Tapatalk

[matabog]

Never done it myself, but from what I heard, if you want to work with the pivot (in any way) you must first soften the material (meaning turning it red, letting it cool down) and then hardening it again.

Good luck with that!

 

 

[praezis]

@ matabog: Oh god, do not heat to red! Light blue is sufficient.

If it is bent 3-4 deg only, danger of breaking is not so high. I do this very often, repairing chronographs. I use to hold the pivot (the straight part) in a lathe collet, turn the spindle and compare the other pivot to the tip of the headstock. Bend the pivot with light taps until the wheel wobbles no more.

Frank

 

 

 

[matabog]

Thank you for the correction! Didn't mean to fool anyone

Edited June 20, 2017 by matabog

[matabog]

But still, how do you harden it again after you've straighten it? 

[anilv]

General answer.

1st step (hardening). Heat red hot and quench in oil.

2nd step (tempering). Heat but not red hot. straw is the usually quoted  colour , then quench again.

The problem is these processes work on larger items where the piece heats up gradually. A small part like a pivot will heat up red-hot practically instantly. You would need to set up a bed of copper shavings and heat this part on it but it pretty hit and miss. There are some good videos on hardening watch parts on youtube.

A replacement would be the way to go.

Anilv

 

[StuartBaker104]

I came across this thread whilst researching re-pivoting earlier. http://mb.nawcc.org/showthread.php?118580-Escape-wheel-pivot-repair

The idea of letting down the temper slightly might appeal. I'm no expert in this, but suspect that re-tempering the whole pinion with wheel attached is going to cause you bigger issues than you have already.

[praezis]

 

I came across this thread whilst researching re-pivoting earlier. http://mb.nawcc.org/showthread.php?118580-Escape-wheel-pivot-repair

The idea of letting down the temper slightly might appeal. I'm no expert in this, but suspect that re-tempering the whole pinion with wheel attached is going to cause you bigger issues than you have already.

You are right. I do not heat at all, but reducing the temper to blue or light blue may help. Tempering again is not needed.

Frank