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1590Re: [mlathemods] Re: live center woes

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  • David Halfpenny
    May 1 7:14 AM
      ----- Original Message -----
      From: "Peter sanders" <psanders@...>

      >David Lee <dsleeI@...> wrote:
      >> A live center turns with the work.
      >
      > A live centre in the headstock though turning with the work
      > is really not rotating about the workpiece per se.

      There's a choice between "live" and "dead" centres at both ends of the
      lathe.

      The oldest, simplest and indeed most accurate form of lathe has two "dead"
      centres - two tailstocks if you like. It is driven by a cord either on the
      work or on a pulley rotating on one of the centres.

      Watchmakers call a dead-centre lathe "turns". Woodworkers tend to call them
      "pole lathes" from the springy pole used to return the cord each stroke,
      though a spring, handwheel or treadle wheel can be fitted instead.

      When I was a youngster I made a metal-working dead-centre lathe out of
      steel flats and studding. I cheated by turning the centres on a
      conventional lathe, but it would have worked just as well had I filed them
      carefully, like our ancestors did.

      So the simplest terminology that fits the bill is to call a centre "dead"
      if the point doesn't rotate, and "live" if it rotates with the work,
      regardless of which end of the lathe.

      Yes that does mean that a pointy bit of metal on a Morse taper becomes
      "live" when fixed in a headstock spindle and "dead" when fixed in a
      tailstock barrel, but hey, you can't win 'em all.


      Just to upset you some more, I was taught in Olde Englande that headstocke
      centres should be softer steel, so that they could be turned accurately in
      the spindle for top-class work, while tailstock centres should be very hard
      to resist wear. So we shouldn't be swopping those point bits of metal
      between ends anyway.
      When I came to fit out a workshop, I couldn't get 2MT soft centres
      anywhere. Has the toolpost grinder killed them off?

      David Halfpenny
      Also 56 and from England
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