Choosing the right Balance Wheel

[AndreiMartin]

Hi guys,

I was on the market to purchase a new balance wheel for my FHF70 movement (non-incabloc). I found the #721 part for the movement but in brackets it says INCA.

Is there any significant difference between balance wheels/staffs used on non-incabloc and incabloc movements?

 

Thank you,

 

Andrei M.

 

 

[mikepilk]

The balance wheel itself is the same but the staffs are different sizes, so you need to find the non-Incabloc version.

[AndreiMartin]

8 minutes ago, mikepilk said:

The balance wheel itself is the same but the staffs are different sizes, so you need to find the non-Incabloc version.

Felt it was something to do with the staff. Seems like I will have an extra part sitting around (since I ordered it) until the right time comes along to use it

Thank you for the reply,

 

Andrei M.

[mikepilk]

Is the old balance wheel/hairspring OK? 

If so, balance staffs are quite cheap - if you have a staking set, you could replace the staff.

[AndreiMartin]

6 minutes ago, mikepilk said:

Is the old balance wheel/hairspring OK? 

If so, balance staffs are quite cheap - if you have a staking set, you could replace the staff.

Wheel and spring are in perfect condition. Was looking at a new staff but no staking set  is there any other method that could be used to replace the staff?

[mikepilk]

Unfortunately not. You need a staking set and a tool (or lathe) to remove the old staff. 

There seems to be plenty of complete balances available on ebay

[AndreiMartin]

31 minutes ago, mikepilk said:

Unfortunately not. You need a staking set and a tool (or lathe) to remove the old staff. 

There seems to be plenty of complete balances available on ebay

Most of what I found were incabloc ones. Put me down a bit for not being focused on that small but significant detail . Might just take it to a local watch repair shop, see if they have some spares.

[nickelsilver]

On balancestaffs.com they say the difference in length between Inca and regular is 0.01mm, Inca shorter. That's a small enough difference that it shouldn't really matter. If the pivot sizes are the same (that's not for sure) it could work, give it a try.

 

Sometimes on calibers like this that had a long life and that are closely related to other movements there are differences in stud diameter and such, but it can't hurt to see if it fits.

[AndreiMartin]

5 minutes ago, nickelsilver said:

On balancestaffs.com they say the difference in length between Inca and regular is 0.01mm, Inca shorter. That's a small enough difference that it shouldn't really matter. If the pivot sizes are the same (that's not for sure) it could work, give it a try.

 

Sometimes on calibers like this that had a long life and that are closely related to other movements there are differences in stud diameter and such, but it can't hurt to see if it fits.

I was literally coming off this website with the screenshot below  

Seems like the difference is very small.

[praezis]

I looked it up for you: the Incabloc staff is just 1/100 mm shorter, other differences don't matter.
Most probably, the Inca type will be fine as replacement.

Frank

edit: 2 members were faster while I was checking - now you have three confirmations 

Edited July 26, 2021 by praezis

[AndreiMartin]

Thank you everyone for the support! I will keep you up to date as soon as it arrives. Fingers crossed

 

[rodabod]

A broader answer is that yes, sometimes the length will be different, and that’s very important, but also the profile of the pivot itself may be different. When shock-protection was introduced, it meant that there were opportunities to change the pivot profile. So, if you compare an earlier original Omega 30T2 staff with a later original Inca version then you will find that the pivots themselves look different. It was once suggested to me that the later Inca pivots may not be as resilient, but I’ve never proven this. 
 

 

 

[nickelsilver]

Rodabod makes a good point. Other than the size of the pivot itself, the form of the staff just after the pivot and its cone is quite specific for Incabloc (and Kif). On an Inca staff, there is a specific diameter after the pivot/cone, this knocks into the side of the hole in the "bloc" as Incabloc calls it, the main setting in the plate or bridge, in the event of a lateral shock. There is then a shoulder just after this diameter, at a specific length from the pivot end, which also hits the bloc, in the event of an axial shock. The hole and cap jewels can move under the spring tension, returning to their proper place; the fact that the bloc and corresponding diameter and shoulder limit movement keeps the spring from flexing far enough to disengage.

 

With all things equal, pivot size and length, an Inca staff should work in a non shock watch without issue. It isn't necessarily the case the other way around, or, if it does work, the shock protection will likely be compromised.

[AndreiMartin]

10 minutes ago, nickelsilver said:

Rodabod makes a good point. Other than the size of the pivot itself, the form of the staff just after the pivot and its cone is quite specific for Incabloc (and Kif). On an Inca staff, there is a specific diameter after the pivot/cone, this knocks into the side of the hole in the "bloc" as Incabloc calls it, the main setting in the plate or bridge, in the event of a lateral shock. There is then a shoulder just after this diameter, at a specific length from the pivot end, which also hits the bloc, in the event of an axial shock. The hole and cap jewels can move under the spring tension, returning to their proper place; the fact that the bloc and corresponding diameter and shoulder limit movement keeps the spring from flexing far enough to disengage.

 

With all things equal, pivot size and length, an Inca staff should work in a non shock watch without issue. It isn't necessarily the case the other way around, or, if it does work, the shock protection will likely be compromised.

Hopefully when I put everything together it will start ticking with no issue  It's a Dogma Prima which I got really attached to and want to fix it. New stem (a previous watchmaker told me she fixed it but only superglued the crown to the old stem), new setting lever spring and the new balance wheel :). Looking forward to it.

[praezis]

On 7/26/2021 at 1:32 PM, nickelsilver said:

It isn't necessarily the case the other way around, or, if it does work, the shock protection will likely be compromised.

You can express it more directly, too: An ordinary staff will rub the narrow opening of an Inca bloc, the "watchmaker" will realize this and - destroy the bloc by filing/drilling. No more shock protection.

Frank

[AndreiMartin]

Not sure if anyone is following this but, the parts have arrived and were fitted in very carefully. Watch started ticking the moment the balance assembly was put in place. Not having a timegrapher yet I will monitor the watch hourly and see how accurate it is.

Feels great to be honest.