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  1. #1

    Default 992 B staff replacement

    I have replaced some staffs that are staked on but never a friction fit.

    My directions are not covered very good in the repair book I have so I was going to do the following.
    Remove form watch the conplete balance
    Remove hair spring
    Remove saftey roller
    Punch the staff from the balance wheel and hub
    Remove the roller table from the staff

    Back together
    New staff prechecked for fit
    put the roller table back on
    Put the staff on the hub and balance wheel
    Put the saftey roller back on
    Put the hair spring on

    The balance wheel is already marked for the roller and hair spring stud
    This will be my first on like this and other points to think about

    Don

  2. #2
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    Default Re: 992 B staff replacement (RE: Don)

    I remove the roller table before removing the staff.

    Removing the staff is fairly straight forward. Standard flat-faced punches are all you need for the Hamilton staffs.

    Here's the most important thing to know, though:

    Friction fit staffs(whether Hamilton or Waltham) consist of the staff itself and a blue steel hub. The hub is riveted to the balance, and stays with the balance.

    When driving the staff out, you need to carefully support it at the hub to avoid driving the hub out of the wheel(rather than driving the staff out of the hub).

    When choosing a stake to support the balance, be sure you pick one just large enough to allow the staff to pass through, but to still support the edges of the blue steel hub.

    Overall, friction staffs are very straightforward and really no problem. Just don't drive the hub out. Not only will you have to replace it, but you'll also have to true and poise the balance. Truing a solid balance-like the 992B-isn't so easy.

  3. #3

    Default Re: 992 B staff replacement (RE: Don)

    Good to know I don't need anything fancy, as I just acquired a K&D Inverto staking set that is almost complete (missing a few punches and a few reamers and pushers, and filthy).

    I also have my father's Hamilton 992B that my brother dropped onto a hardwood floor, shearing off the pivots on the balance, so I will replace it once I get the parts and the staking set cleaned up some and sorted out.

    Do I need to use a special punch for the pivot end of the old staff, or can I use a flat or round one? Or is there a shoulder for the hairspring collet that a flat punch will sit on? I've not closely examined the balance yet, just verified that it was indeed broken. I'll have to take a look at the jewels, too, of course.

    Peter

  4. #4
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    Default Re: 992 B staff replacement (RE: psfred)

    The K&D #39 stake is designed for driving out Waltham staffs, although I imagine it would work well on the Hamilton staffs too. K&D #18 sets had these when new, so yours should have one unless it's been lost over the years.

    When I did mine, I just used a standard flat face punch that just fit over the pivot shoulder. I had no trouble doing it this way.

    While we're on the subject of stakes, though, if you're going to do Waltham friction staffs, you'll also want stakes #40, 41, and 42. These are specifically designed for driving the Waltham detachable staffs back IN the hub. #40 is the one I've always used for 16 size 1899/1908 staffs(#4860 and #4861). These three should also be included in a K&D #18.

  5. #5

    Default Re: 992 B staff replacement (RE: ben_hutcherson)

    Thanks Ben.

    I'll have to clean and sort out all the punches. So far none seem to be corroded, just a bit of surface rust and dirt, but we shall see. There are a few missing, but the correct stumps are there for Waltham frictions staffs, so the punches should be as well.

    I don't suppose one would need to worry much about damaging a balance staff with the pivots broken off, eh?

    Peter

  6. #6

    Default Re: 992 B staff replacement (RE: psfred)

    Thank you

    I will look it over carfully. It looks like the staff is in through the botton of the hub and the roller table is between the balance hub and the larger collor of the staff. Boy does that make sence?

    Unless the one I have was put together wrong?

    I have another one that runs and have never had the complete balance out so will compair.
    Don

  7. #7
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    Default Re: 992 B staff replacement (RE: Don)

    Don, as you know already it is a friction fit staff and therefore you need to be careful and keep it away from the lathe.

    Be careful not to damage the balance wheel.

    Look here, this is the order the parts are supposed to be fitted in:

    http://www.horologist.com/balance_staffs.htm

    Take it easy and good luck!

  8. #8
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    Default Re: 992 B staff replacement (RE: MFRC1956)

    Don,

    Looking at my 992B, I can see why you might think that the staff would have to come out before the roller table.

    I can assure you, though, that unless something's really been messed up, the roller table will come off before the staff comes out.

    Peter,

    "I don't suppose one would need to worry much about damaging a balance staff with the pivots broken off, eh?"

    I'd agree with you on that in general. I do always like to measure the old pivots, though, and if the removal operation is going to damage the one good pivot, I have to remember to do it before removing the staff.

    My #39 stake is constructed in such a way that it will ruin pivots if they're still intact.

  9. #9

    Default Re: 992 B staff replacement (RE: ben_hutcherson)

    I believe one is gone entirely and the other is severely bent --it's been a while since I looked at it. I wouldn't trust any measurement from the bent one, anyway.

    I do plan to check the jewels (will do a clean and oil and new mainspring too) and check the fit of the new staff before assembling.

    The watch took quite a bashing, I cannot pull the stem out so will have to loosen the bridge, I expect, to uncase it.

    I could thrash my brother, he really doesn't get delicate things and insisted on wearing the watch. He's dropped two other pocket watches, too -- his wife finally bought him a quartz one.

    Peter

  10. #10
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    Default Re: 992 B staff replacement (RE: psfred)

    Peter,

    As far as I know, all 992Bs used the same size pivot, so that's not too much of a problem. Pivot measuring is more for watches where the same staff is used in multiple grades of watch-like the Elgin 867(18 size full plates) or Waltham 4861(1899/1908 16s).

    In any case, though, I'd suggest that when you order the staff, be sure you get a factory staff. My experience is that the factory staffs will always drop right in with no trouble. The Swiss aftermarket staffs are hit-or-miss.

  11. #11

    Default Re: 992 B staff replacement (RE: ben_hutcherson)

    thank you all I did look up the above web sight and it may be that the saftey roller is larger than I think and the diagram for the walthamis like that too.

    When I get the saftey roller off then I will see what you are toalking about.

    I will go slow and on the week end when more refreshed.

    Don

  12. #12

    Default Re: 992 B staff replacement (RE: ben_hutcherson)

    The staff is in and all back to gether and it is been running now for almost 24 hours and is doing good. Thank you all fo rall the help. This was my first friction fit staff and was a pleasent repair.
    All went good
    Don

  13. #13
    Registered user. MFRC1956's Avatar
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    Default Re: 992 B staff replacement (RE: Don)

    Good job Don! Always nice to know how things turned out in the end.

    Friction fit staff replacement is a walk in the park, I can imagine the relief when this type of staff came along.

    Michael

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