Pianotech

Key Button stress fractures

  • 1.  Key Button stress fractures

    Posted 02-21-2018 09:14
    Edited by Jim Ialeggio 02-21-2018 09:14
    Falconi 74, 30 years old.  Doing an action job. According to plan, keys were to be bushed. Dave,my son, who does most of this work,  looks carefully at the key buttons before removing the bushings, an  calls me over. Its hard to see, which is why I'm not posting a pic...but most every button has  2 stress fractures running the length of the button along the edges of the mortise. Keys in otherwise excellent condition...much better than most keyboards I work on.

    We gently wedged the mortise to see if the cracks were just visual or not...not...the cracks are cracks and move when the key is put back on the frame. So we're making some buttons and doing a button job.

    The thing is, that this kind of stress induced fracture could only have been created if these mortises had been "punched" rather than cut. Not sure how large button manufacturing operations make their mortises, but a cut mortise would not have had this failure. Hollow chisel mortisers make a punch of a sort, but the interior wood of the mortise is removed by a drill bit. The chisel edge punch is fairly belligerent but not a wedging punch. I have not seen a hollow chisel mortise small enough to make mortises, and the sides of the mortise do not have telltale indications that suggest a hollow chisel was used. I'm betting these were made by some sort of metal-working style punch-and-die setup...bad idea. I do know the bushing indentations in front mortises, were often crushed, prior to making the mortise, rather than cut.


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    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
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