The balance staff on a UNITAS 6310N movement cannot be riveted in place

[StephanC]

Hello and Happy New Year,

I am currently replacing a balance staff on a UNITAS 6310N movement. The new staff, marked 13-6310N, has the correct dimensions but the height of the rivet part was exactly the same as the thickness of the balance wheel, i.e. the rivet is flush with the hole, see picture.

Have any of you experienced something similar? Could there be several versions of the 6310N balance staff?

Thank you very much for a reply in advance that will lead me in the right direction and get my spirits back.

[nickelsilver]

The rivet will still expand with a convex punch, might as well try and see how it holds. Yes, they generally should stick up a few hundredths of a mm.

[StephanC]

9 minutes ago, nickelsilver said:

The rivet will still expand with a convex punch, might as well try and see how it holds. Yes, they generally should stick up a few hundredths of a mm.

Thanks,

Yes. I think I will give it a harder hit. If that does not work, plan B is Loctite  (just kidding)

Edited January 7 by StephanC
misspelling

[nickelsilver]

Check your punch(es). Often the part that actually makes contact gets flattened over time, and they need a little touching up to be nicely convex again.

[StephanC]

1 minute ago, nickelsilver said:

Check your punch(es). Often the part that actually makes contact gets flattened over time, and they need a little touching up to be nicely convex again.

Excellent. I will.

[Neverenoughwatches]

40 minutes ago, StephanC said:

Hello and Happy New Year,

I am currently replacing a balance staff on a UNITAS 6310N movement. The new staff, marked 13-6310N, has the correct dimensions but the height of the rivet part was exactly the same as the thickness of the balance wheel, i.e. the rivet is flush with the hole, see picture.

Have any of you experienced something similar? Could there be several versions of the 6310N balance staff?

Thank you very much for a reply in advance that will lead me in the right direction and get my spirits back.

What's the hole in the balance wheel like ?

Edited January 7 by Neverenoughwatches

[StephanC]

9 minutes ago, Neverenoughwatches said:

What's the hole in the balance wheel like ?

The hole is perfectly round and in good shape. The staff is sitting snuggly.  I guess, if I hit the staff hard it will expand.  It is not enough material to create a rivet. I will try tomorrow. 

3 minutes ago, StephanC said:

The hole is perfectly round and in good shape. The staff is sitting snuggly.  I guess, if I hit the staff hard it will expand.  It is not enough material to create a rivet. I will try tomorrow. 

Maybe I should counter sink the balance hole just a small amount to give the punch more room to expand the rivet? Now the punch hit the balance almost at the same time as the rivet.

[Neverenoughwatches]

34 minutes ago, StephanC said:

The hole is perfectly round and in good shape. The staff is sitting snuggly.  I guess, if I hit the staff hard it will expand.  It is not enough material to create a rivet. I will try tomorrow. 

Maybe I should counter sink the balance hole just a small amount to give the punch more room to expand the rivet? Now the punch hit the balance almost at the same time as the rivet.

Not in all cases but the wheel should have some evidence of the old staff...a slight seat where the rivet was situated. For this reason when staffs are cut out with a graver, the hub side is cut rather than digging out the rivet. Do you have a picture of the wheel... collet side. 

[StephanC]

9 minutes ago, Neverenoughwatches said:

Not in all cases but the wheel should have some evidence of the old staff...a slight seat where the rivet was situated. For this reason when staffs are cut out with a graver, the hub side is cut rather than digging out the rivet. Do you have a picture of the wheel... collet side. 

 

[AndyGSi]

How did you remove the old balance staff?

[StephanC]

15 minutes ago, AndyGSi said:

How did you remove the old balance staff?

I used a jewelling tool and slowly pushed the staff out. The chance of the rivet breaking without damaging the balance is quite high according to a Rolex service workshop.

I have done it a few times without damaging the balance.

I have also used a punch and hammer once but it did not work well at all. If I had a lathe, that would probably have been the safest thing to do. 

[Neverenoughwatches]

2 hours ago, StephanC said:

 

Can't tell for sure but it looks like it has a slight sink for the rivet.

34 minutes ago, StephanC said:

used a jewelling tool and slowly pushed the staff out. The chance of the rivet breaking without damaging the balance is quite high according to a Rolex service workshop.

That does apply to a particular staff that Rolex used.

[AndyGSi]

34 minutes ago, StephanC said:

I used a jewelling tool and slowly pushed the staff out. The chance of the rivet breaking without damaging the balance is quite high according to a Rolex service workshop.

I have done it a few times without damaging the balance.

I have also used a punch and hammer once but it did not work well at all. If I had a lathe, that would probably have been the safest thing to do. 

Looking at the balance there can't have been much of a rivet on the old one.

How does the old shoulder compare to the new one?

[StephanC]

4 minutes ago, Neverenoughwatches said:

Can't tell for sure but it looks like it has a slight sink for the rivet.

Yes, but a very small sink. I think it will work to rivet the staff with little more force.  

[Neverenoughwatches]

12 minutes ago, StephanC said:

Yes, but a very small sink. I think it will work to rivet the staff with little more force.  

Extra force is rarely a good thing in watchmaking.

Maybe the reason the rivet isn't spreading is because the width of the stake is too big.

Edited January 7 by Neverenoughwatches

[StephanC]

4 minutes ago, AndyGSi said:

Looking at the balance there can't have been much of a rivet on the old one.

How does the old shoulder compare to the new one?

The rivet shoulder was broken into two parts. A small ring, the rivet part of the shoulder and the rest of the staff. It looks that old shoulder is a bit higher but it is difficult to say for sure. Tomorrow I will give the staff a real hit. I think I have been to gentle. 

[nevenbekriev]

Yes, You can use big drill bit to make some countersink on the balance arm. 0.1 mm is enough height of the rivet above the surface of the arm

[Neverenoughwatches]

2 minutes ago, StephanC said:

Tomorrow I will give the staff a real hit. I think I have been to gentle. 

all parts on a movement are delicate.  Imagine the rivet is only a thin piece of metal. What you need to be sure of is that the stake is pushing the rivet out and down. The dome of the stake must be narrow enough to get inside the rivet to push it outwards.

We had a really good discussion about this around a year ago with some good pictures that visualised the proceed .

[StephanC]

23 minutes ago, Neverenoughwatches said:

Can't tell for sure but it looks like it has a slight sink for the rivet.

That does apply to a particular staff that Rolex used.

Ok, I didn’t know, but it has worked very well so far. It feels better than the punch technique. One day I hope I have a lathe. That must be best way to remove a staff.  

 

3 minutes ago, Neverenoughwatches said:

all parts on a movement are delicate.  Imagine the rivet is only a thin piece of metal. What you need to be sure of is that the stake is pushing the rivet out and down. The dome of the stake must be narrow enough to get inside the rivet to push it outwards.

We had a really good discussion about this around a year ago with some good pictures that visualised the proceed .

Yes, I will check the dome tomorrow and see how it fit the rivet. I think you are right. It can be the case that the punch is not pressing the rivet out. I bought three staffs and I will offer one and punch it without the balance in order to study how it deforms.

17 minutes ago, nevenbekriev said:

Yes, You can use big drill bit to make some countersink on the balance arm. 0.1 mm is enough height of the rivet above the surface of the arm

Yes, I will do that. Thanks.

Thanks everybody for splendid inputs. 

[Klassiker]

4 hours ago, StephanC said:

Now the punch hit the balance almost at the same time as the rivet.

It sounds like you are not using a punch with the correct dome on the end. The punch should only strike the angled face of the undercut on the rivet. The idea is to swell this slightly to sit tightly in the hole. Once it is tight, use a flat faced punch to finish off. Ideally, this will create a very small lip to make sure the balance stays bedded down. If you use too much force, and if you put a chamfer on the hole in the balance, which you then try to fill in by forming a head on the rivet, you could swell the staff, expanding or even cracking the hole in the balance.

[nevenbekriev]

I can not confirm by observing this personally, but OP says the rivet is not high enough and not popping at all above the surface of the balance arm. In this case using flat punch will be wrong as it will deform the balance arm. So only domed or conical punch may be used to rivet the staff that will be able to act on the rivet but will not hit the arm.

[StephanC]

13 hours ago, Neverenoughwatches said:

Extra force is rarely a good thing in watchmaking.

Maybe the reason the rivet isn't spreading is because the width of the stake is too big.

Yes, the problem is identified. The punch is of poor quality. Far too soft. In addition, it is too flat in the immediate vicinity of the hole. Dome has no effect. Staff sits well in the punch. No play.

There are clear traces in the punch from the staff shoulder but the staff shoulder is completely intact, i.e. all the force has deformed the punch.

The natural thing to do now is to cancel until I buy a proper staking set. Bergeon is very expensive for a hobbyist. I see that Cousins sells a Value Staking set from India that is hardened. To buy a good used set on Ebay you have to be really lucky I would think.

A last attempt could be to file a more conical shape on the bad punch, heat the tip and then dip it in oil in an attempt to harden it. Nothing to lose as it is completely useless. Thanks for all the input.

13 hours ago, nevenbekriev said:

I can not confirm by observing this personally, but OP says the rivet is not high enough and not popping at all above the surface of the balance arm. In this case using flat punch will be wrong as it will deform the balance arm. So only domed or conical punch may be used to rivet the staff that will be able to act on the rivet but will not hit the arm.

It is bad design domed punch and too soft (not harden) that is the root problem.  

13 hours ago, Klassiker said:

It sounds like you are not using a punch with the correct dome on the end. The punch should only strike the angled face of the undercut on the rivet. The idea is to swell this slightly to sit tightly in the hole. Once it is tight, use a flat faced punch to finish off. Ideally, this will create a very small lip to make sure the balance stays bedded down. If you use too much force, and if you put a chamfer on the hole in the balance, which you then try to fill in by forming a head on the rivet, you could swell the staff, expanding or even cracking the hole in the balance.

Yes, you're absolutely right. The punch is the root problem. Cheap Chinese. I should know better. Now on staking set hunting.

[nickelsilver]

You should be able to reharden the punch. Reshape it, as you don't have a lathe, chuck it in a drill and use stones to get a nice shape. Heat just the end (a centimeter or so) to orange, quench in oil nice and vertically. When you come out of the quench stick the oily tip back in the flame to ignite the oil, let it burn a few seconds (it may just burn out)- that will suffice for the tempering.

[StephanC]

38 minutes ago, nickelsilver said:

You should be able to reharden the punch. Reshape it, as you don't have a lathe, chuck it in a drill and use stones to get a nice shape. Heat just the end (a centimeter or so) to orange, quench in oil nice and vertically. When you come out of the quench stick the oily tip back in the flame to ignite the oil, let it burn a few seconds (it may just burn out)- that will suffice for the tempering.

Excellent. Thanks. That confirms my plan to use my drill as a lathe. (one day I will have a lathe on my working bench)   

[fellerts]

Whereabouts in Norway are you? I have an excess of Boley and Bergeon punches from an estate sale that I have no use for. Maybe I have the punch you need. Feel free to PM me