Re-pivoting

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  • #48043
    jgauntt
    Participant
    • Topics Started: 1
    • Total Posts: 2

    You have another Newbie here, and I may have gotten in over my head.
    I wanted to learn more about clocks and how to repair them and I can see this being a really fun hobby.
    I have an Elgin mantle clock that needed work and it made a great first project. For my second project I took on an old french clock belonging to a friend. It didn’t work and he used it for decoration sitting on a shelf and we both figured that I could do it no harm. All it needed was a new suspension spring and a good cleaning and oiling and it keeps time great. When I was putting it back together I broke the pivot on the “fan” arbor on the chiming mechanism. The arbor is about 28mm long and about 1mm dia. and the pivot is about 0.5mm. I watched Bob’s lathe video about re-pivoting, got a set of very small drill bits and an assortment of pivot wire, made a “flag” out of a piece of angle aluminum, chucked it all up in my Unimat SL lathe and started trying to drill out the pivot hole in the end of the arbor but I am barely making an indention in the end of the arbor. My question is, is this arbor made of a hardend steel and therefore I’m not using the right type of drill bit? Or am I going about it all wrong?
    Any advice is welcome
    thanks,
    Jack

    #50598
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Good to see you here Jack,
    1mm diameter is beginning to get down there in size. As you move into smaller clocks and larger watches you’ll find that holding close tolerances in your tooling becomes more important. At these smaller sizes applied drill jigs (flags) should be made of steel and all bearing surfaces, such as the champfer used for locating the end of an arbor, should be polished smooth. If using a high carbon steel then hardening and polishing these tools will serve you well. Spade rather than twist drills are also better to use when dealing with smaller arbors. To test the hardness you can draw a fine jewelers file across the end of the arbor to see if it “cuts” the metal. If not then you will need to anneal this section of the arbor before drilling. Also if pivoting smaller pieces is new to you then it’s probably a good idea to practice on a few scrap arbors or tiny pieces of steel before tackling that arbor to get a feeling for the tooling.
    Good luck and please let us know how it goes Jack,
    Enjoy,
    Bob

    #50599
    ihsfab
    Participant
    • Topics Started: 1
    • Total Posts: 9

    Jack,

    I have found that putting a new pivot in a French movement to be rather difficult. I have found them to be very hard even after annealing the shafts. They are not fun to say the least.

    Kenton

    #50600
    jgauntt
    Participant
    • Topics Started: 1
    • Total Posts: 2

    Kenton, thanks for the encouragement! :)
    This clock repair is turning into more than just cleaning, oiling, and setting!! I had to read up on “annealing” then cautiously started the process. Well, long story short – I got the pivot drilled out and replaced. It was quite a learning process. Next is to polish the pivot and re-assemble the movement.
    Thanks for the help. I am really enjoying this new challenge. I am sure you will be getting more questions from me.

    Jack

    #50601
    ihsfab
    Participant
    • Topics Started: 1
    • Total Posts: 9

    Jack

    Glad to hear you had success on installing a new pivot. :D

    Kenton

    #50602
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Congrats Jack!
    Not an easy feat at that size.

    Bob

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jgaunttRe-pivoting