Boring bar chatter cure... I don't believe it! - Page 2
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  1. #21
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    Quote Originally Posted by Nmbmxer View Post
    I verify by tightening the rest and see if the chatter comes back.
    Did that. It did.
    BUT, on my next production run I needed the bar out farther to about 4xD. Tried with one set screw and it was awful. Tightened them all... beautiful.

  2. #22
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    Quote Originally Posted by JBNimble View Post
    Did that. It did.
    BUT, on my next production run I needed the bar out farther to about 4xD. Tried with one set screw and it was awful. Tightened them all... beautiful.
    So on one job one screw good and all tight bad, on another one screw bad and all tight was good?
    Add the front or back screw as what works.
    How does one choose? What the heck is going on here? It has to be more than just simple resonance and sing frequency.
    Bob

  3. #23
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    Quote Originally Posted by CarbideBob View Post
    How does one choose? What the heck is going on here? It has to be more than just simple resonance and sing frequency.
    Bob
    I believe the idea is moving the bar’s resonant frequency either above or below the excitation frequency from the cut. So adjusting machine parameters can affect the excitation frequency and adjusting bar clamping will affect the resonant frequency. It should be a fairly narrow peak that one wants to avoid, so either direction can work.

  4. #24
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    Quote Originally Posted by wesg View Post
    With the holder just hanging on the dovetail?

    I've had mine either vibrate loose ... or I forgot to tighten it ... and it cuts just beautiful. Insert OD turning tools mostly. 4140PH, 416, maybe some alum. Holds dimension too. Weird.
    Yuh, weeeeeeaaaad

  5. #25
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    Any oscillating system has a 'Q' (or goodness) factor. The higher the Q the less losses and it's easier to maintain oscillation.

    What you've done is to lower the Q.

    The old blacksmiths trick of wrapping a chain or heavy rope around his anvil to stop it ringing is exactly the same principal.

    The WW2 Japanese Zero fighter plane had fluttering flaps at high dive speeds iirc that they added weights to on the leading edge and lowered the Q to cure the problem.


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