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Gooseneck & rigidity?

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  • Gooseneck & rigidity?

    In the tangential toolholder thread (which I don't want to hijack) "Gary Paine" posted a picture of a tangential toolholder with a gooseneck.

    I appreciate that this was engineering of a different era but what was the logic? Certainly not rigidity...

    Then again, were the old-timers onto a good thing that got lost in time?

  • #2
    I don't know specifically about the goose neck with regard to tangential tool holders, my Diamond tool holder never causes chatter. I can tell you that some tool holders are engineered to give what I'll call a "controlled lack of rigidity" that actually helps eliminate chatter. It sounds counter intuitive and some of the real machinists and engineers here can probably give it a better name than mine and explain the science behind it. All I know is that it works at the times it is needed. I have a cut off tool holder designed with a slot cut behind the area that holds the blade effectively making it a goose neck style and it eliminated the chatter I was experiencing with a rigid cut off tool holder when I used a lantern tool post. I suspect that the goose neck allows flex at a frequency that opposes the flex in the lathe and lantern post and they effectively cancel each other out. Probably like some of the new sound control techniques that use sound to cancel out sound.

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    • #3
      That's the first gooseneck tangential tool I've seen, but goosenecks were commonplace in the first half of the 20th century.

      I have a really nice Armstrong gooseneck I've been wanting to try -- the idea being that it flexes down away from the cut instead of digging in.
      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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      • #4
        The idea seems to be that the center of flexing is located above the cutting point. This moves the cutting point away from the work when the cutting pressure increases instead of into the work. You can accomplish something similar by setting the tool point well below the lathe centerline but that messes up the cutting angles.
        Don Young

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        • #5
          ^^^ What Don said. It flexes down and out, thereby lightening cutting load and preventing chatter. I posted a link to a PM thread not long ago where someone posted a scan of a book explaining how it worked, with the book being from 1890-something, IIRC. Interesting stuff.

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