Pianotech

  • 1.  Back action flange pinning repair

    Registered Piano Technician
    Posted 08-10-2023 22:14

    I'm going over my Knabe C back action and noticed some flange pins are working their way out. It appears that all of the flanges are glued in, and removing them would be a bit of a nightmare. Replacing the back action isn't my best option right now, so any advice on a repair? I'm thinking about inserting some small shims between the flanges to hold the pins in place. Am I missing something obvious?

     Thanks!



    ------------------------------
    Tim Foster RPT
    New Oxford PA
    (470) 231-6074
    ------------------------------


  • 2.  RE: Back action flange pinning repair

    Registered Piano Technician
    Posted 08-10-2023 23:32
    Hi Tim

    The reason the pins are moving out, referred to as reverse pinning, is because the wood in the lever has "shrunk".  The proper way to fix this is to repin with a larger pin which may also require a little reaming of the bushing cloth. 

    You have one of two choices. 
    1. Break the glue joints, repin, and glue it all back together. 
    2. Insert shims, as you suggested.

    There is a 3rd option. but you already said you don't want to do that.

    Wim



    Original Message


  • 3.  RE: Back action flange pinning repair

    Registered Piano Technician
    Posted 08-10-2023 23:40

    Thanks, Wim, I went ahead and shimmed. Hopefully it gets me by for a few years and I'll put a new back action in at some point



    ------------------------------
    Tim Foster RPT
    New Oxford PA
    (470) 231-6074
    ------------------------------

    Original Message


  • 4.  RE: Back action flange pinning repair

    Posted 08-10-2023 23:59
    Hi,

    What Wim said, plus, before breaking the glue joints, drill through the flanges into the rail' and install small screws. I prefer #4 or #6 x 3/4", depending on the thickness of the flange and the rail. Carefully done, most of the flanges will not split out; and the repair can be done without changing the original geometry...unless one should as part of the repair.

    Kind regards.

    Horace




      Original Message


    Original Message


  • 5.  RE: Back action flange pinning repair

    Registered Piano Technician
    Posted 08-13-2023 01:00

    Anyone who has cause to pull a back action that does not have the flanges screwed to the rail would be well advised to insert screws through the flanges. Perhaps clamping the flange somehow to minimize flange cracking while drilling. I was called in to replace a broken agraffe by another tech on a Steinway that was rebuilt 10 - 15 years ago. Original back action with glued flanges. When the agraffe snapped, it broke the flange glue joint. We ended up having to quickly pull the back action because we were just not really able get at the flange well enough to to make a good glue repair. Screws might have made the difference.



    ------------------------------
    Tremaine Parsons RPT
    Georgetown CA
    (530) 333-9299
    ------------------------------

    Original Message


  • 6.  RE: Back action flange pinning repair

    Registered Piano Technician
    Posted 08-12-2023 10:39

    You may want to consider first scribing all the flanges on the back,  then install bridge pins, screws or small brads to lock the flanges in place.  Next

    use an iron to remove the fixing rail.  Then repin/rebush.  



    ------------------------------
    Parker Leigh
    Winchester VA
    (540) 722-3865
    ------------------------------

    Original Message