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stretching music wire

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  • #16
    Originally posted by beanbag
    If you just buy normal "music wire" from the hardware or hobby store, what alloy is it?
    Dunno the alloy, probably anything above 1045 or so, but "very hard" it is NOT, and CAN NOT BE.

    "Music" wire is wrapped around a peg, and tightened, in "musical" use..... it HAS to be annealed back to a low temper, somewhere in the blue range, or it would BREAK.

    it still is substantially harder than dead soft wire, but....
    1601

    Keep eye on ball.
    Hashim Khan

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    • #17
      Forget the heat

      I have used stretched music wire for several years. At one time Machineries Handbook included instructions for the setup and measurements an I used them for aligning sawmill carriage rails. The basic setup was a pair of pulleys, one at each end of the wire. Weights were applied at both ends until the wire starts to yield. At that point, the wire is as straight as it's going to get and the only correction is for the sag due to the effects of gravity.

      When released, the wire turned into a rats nest due to the yielding. At that point, it is easiest to just throw the wire out. We bought it in spools of several hundred feet.

      An alternate way we used was to set up blocks at the ends with cross drilled studs. The wire was put through the stud and locked with a tapered pin. The wire was then pulled to snug with the studs and then pulled an additional 3% of the wire length to get beyond 2% offset yield. This would be an easier approach for a shorter straight edge.

      The downside of a stretched wire straightedge is that any contact with the wire generates a deflection. We used an electronic contact sensor that allowed vertical adjustment to .00005 and took the reading at the point that the sensor lost contact.

      On a short length, I would suggest the possibility of stretching the wire and then filling under it with epoxy to support the wire. In the end, I think you will do better to purchase or scrape a rigid straight edge.

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