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Tuning Lever Screw Threads

  • 1.  Tuning Lever Screw Threads

    Posted 05-06-2021 00:11
    I see Dan Levitan's C lever he says on his webpage:

    "the joint is welded, not threaded. Only a few of the threads carry most of the stress in even the most carefully machined threaded joint, so a threaded joint significantly reduces the stiffness of a tuning lever."

    How much stiffness is actually lost? I see that he has a tube of welded steel which I'm sure is stiffer than ordinary solid steel core levers, but how does it compare to the carbon fiber shaft/aluminum threaded-joint Fujan levers?

    Why not just combine both and have a carbon fiber shaft with aluminum welded joints? Wouldn't that be the stiffest lever yet?


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    Cobrun Sells
    cobrun94@yahoo.com
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  • 2.  RE: Tuning Lever Screw Threads

    Registered Piano Technician
    Posted 05-06-2021 00:57
    The original steel shaft heads have tapered threads like on a pipe. The thread itself holds the two pieces together. The Fujan lever has straight threads and both pieces butt up against each other, which provides a superior fit, and it's much stiffer. The joint strength doesn't depend upon the threads themselves but the flat surfaces of the shaft and the head held against each other. The diameter of the two pieces on the Fujan is much larger than on the solid steel shaft lever, which gives a much larger surface area for contact and more strength.

    Removing and replacing the head on a steel shaft lever repeatedly probably weakens the junction, and it does eventually gets loose. I purchased a tap and die set for repairing my steel tuning hammer because it had gotten loose over time.
    As far as welding the aluminum, you could do that, but I doubt it would be any stiffer, and you couldn't change the head on it. I have both the Levitan C lever and a Fujan. How stiff do you need or want it to be? I can't detect any flex in either of them. I don't have a way to measure how much they flex. They are both excellent choices.

    Paul McCloud
    San Diego


    Cobrun Sells:

    I see Dan Levitan's C lever he says on his webpage:

    "the joint is welded, not threaded. Only a few of the threads carry most of the stress in even the most carefully machined threaded joint, so a threaded joint significantly reduces the stiffness of a tuning lever."

    How much stiffness is actually lost? I see that he has a tube of welded steel which I'm sure is stiffer than ordinary solid steel core levers, but how does it compare to the carbon fiber shaft/aluminum threaded-joint Fujan levers?

    Why not just combine both and have a carbon fiber shaft with aluminum welded joints? Wouldn't that be the stiffest lever yet?

    ------------------------------
    Cobrun Sells
    cobrun94@yahoo.com