CAUT

  • 1.  Replacing grand backchecks- Drilling angle

    Registered Piano Technician
    Posted 10-02-2018 12:26
    All-

    A question for those of you who do this regularly. This relates to a new class I am preparing. When replacing grand backchecks , what is your drilling method- Use the existing holes regardless of their angle? Establish a new location and, if so,  drill angled or 90 degrees to the key? Other than the potential for  less bending, drilling the key and installing at an angle is more cumbersome for me than drilling 90 degrees. Is there a functional reason to drill at the desired  72 degrees that is talked about? It would seem to me the backcheck needs to occupy  the same place in relation to the tail  to function correctly regardless of how it is fixed to the key. Some difference in the resistance of the wire in check with a difference in angle? WNG drills at an angle. I guess it hasn't  been talked about that I remember. Perhaps another instance of a traditional way being preserved. Perhaps  I am also taking this a bit to seriously....

    Many thanks in advance-

    Best from Texas-

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    David Brown
    Garland TX
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  • 2.  RE: Replacing grand backchecks- Drilling angle

    Registered Piano Technician
    Posted 10-02-2018 14:37
    My own take is that this is simply a question of factory procedures. If you are set up to drill the angle and insert the wires and checks, you already have the angle, and those prepping the action have minimal work and are less likely to screw things up. Steinway drills and installs 90 degrees, and has a particular tool set up to make the right bend in each wire, taking maybe a couple seconds each (put the key in place, press a button, remove and place another key).

    For us in doing work in the field, it is a matter of preference. It is easier to drill and install at 90 degrees, but making the angle consistently for 88 keys is somewhat of a challenge. It is not that hard to set up an inclined table to drill at a consistent angle (having center punched), and the drill press can be used to press the checks and wires home. Six of one, half a dozen of the other.
    Fred Sturm
    fssturm@comcast.net
    www.artoftuning.com
    http://fredsturm.net
    "Tradition is not the worship of ashes, but the preservation of fire." -Gustav Mahler




  • 3.  RE: Replacing grand backchecks- Drilling angle

    Registered Piano Technician
    Posted 10-03-2018 09:59
    With drilling at an angle, the wires sometimes are too close to the inside edge of the backcheck blocks and the blocks crack in that spot. An argument for the 90 degree drilling is that the wires are stiffer that way and the backchecking firmer. The holes in backcheck blocks are also less likely to elongate because the end grain holds the wires exactly perpendicularly. At an angle the wood grain starts getting crushed to some degree.

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    Mario Igrec, RPT
    http://www.pianosinsideout.com
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  • 4.  RE: Replacing grand backchecks- Drilling angle

    Posted 10-03-2018 15:04
    David,

    Once I set up my drilling jig many years ago at the ~70 degree angle then drilling at that angle is as easy as drilling at 90 degrees (just being careful about bit drift). I always at least check to see if the holes were located where they should be. If they were and if they were drilled at an angle, great. If not, I plug and re-drill and/or re-locate the holes. I have pretty much always drilled at an angle because it makes sense to me that if I have to bend them at that angle, why not drill them at the angle and minimize the amount of bending I have to do. Thus I have plugged more than a few backcheck holes over the years. 

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    Alan McCoy
    (509) 999-9512





  • 5.  RE: Replacing grand backchecks- Drilling angle

    Registered Piano Technician
    Posted 10-05-2018 11:08
    Many thanks to all who responded! So many clever ideas and forward thinking. The increased stiffness of the wire at 90° was kind of where I was headed with my thinking. Also the increased regulation capacity an advantage to 90° I think.

    One more random thought.... the check end of the key sits lower than the front, yes? So as it rises the check moves farther away from the player until  the key reaches level or parallel. The tail sits well below level so also moves away from the player ( i know... the whole distal proximal thing...) with a much shorter radius.
    So as the key rises the check and hammer tail move away from the player but the hammer much more quicky. Arcing reduces the thickness of the tail and effectively its distance from the backcheck.  Bill Spurlock had a great handout about this for the tail arcing jig saying with correct tail length and arc and correct check placement and adjustment that the space between the check and tail will remain roughly  constant as they rise together. I have found this to be the case for me. The check being mostly parallel to the hammer head at rest also is a good starting point as to angle for me.

    Not sure if I am even asking a question but definitely sure I am missing something. Mainly curious if my thinking is reasonably clear on these points.

    Very grateful for the group.

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    David Brown
    Garland TX
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