CAUT

  • 1.  Hammer bore geometry

    Registered Piano Technician
    Posted 2 days ago

    I am hanging new hammer assemblies on a 1987 Yamaha C5. After carefully measuring the string height and hammer center heights, calculating the bore, everything looks like it should work out fine. But - the hammer shanks are buried in the rest cushions at typical hammer blow. The original hammers were bored shorter and so the shanks were resting comfortably above the cushions (well, would have been if the action had been regulated recently). I believe that Yamaha spec is for zero degree rake. So why can't I get this to work out? It won't regulate properly if can't get the shanks off the cushions. Has anyone else encountered this problem? 



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    Dave Conte, RPT

    Piano Technician in Residence
    The University of Tennessee
    College of Music
    Knoxville TN
    (817) 307-5656
    Owner: Rocky Top Piano
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  • 2.  RE: Hammer bore geometry

    Posted 2 days ago
    Hi-

    Yamahas are not zero degree rake.  The strings are a bit higher and they pitch them back by varying degrees. I have a chart I use to calculate rake by given string height and I think that formula was originally put together by Nick Gragavne.  In any case, at least once I did choose to go with straight on zero rake on a C5 with thinner rest cushions and that piano turned out great,  but can't say if that's to credit. 

    Best,
    D. 

    Dennis Johnson, R.P.T.
    Facebook.com/johnsonpianoservice
    (612) 599-6437  (cell)



    Original Message