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String Stretch


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  • String Stretch

    I work for a manufacturer of high quality steel wire,some of which is used for guitar strings.

    I asked our chief engineer about stings "stretching in" and he feels that what is really happening is that the strings are not stretching but the slack is pulling out. If the yield strength or elasticity of the strings is not exceeded they will not change . 

    Any thoughts?

  • #2
    he is correct imo


    • #3

      Just ballparking a calculation for a .010 E string:

      15 pounds string force divided by (pi times 0.005" squared) = 191,000 psi


      Ernie Ball puts their string steel ultimate tensile strength at a bit over 400 kpsi.  Just guessing that the yield strength is in the ballpark of 70% of the UTS, there is quite a bit of margin during tuning and playing before actual stretching would occur, but not so much you can't yield them if you are not careful while trying to "prestretch" them.  You don't want to pull too hard on them.

      I've always thought that what you are doing when you pull on freshly installed strings is seating the ball, taking any play out of the wraps on the tuning peg, and reducing the radius (by yielding in bending) where the string goes over the bridge and, to a lesser extent, the nut.  If you look carefully at the string where it goes over the bridge before you pull it, you can see the smooth curve.  After you pull it, the curve is much tighter.