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  1. #1
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    Aug 2015
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    10

    Boring 6061 - horrible surface finish!

    I am attempting to bore 65mm holes in 4" aluminum bar. A photo of the result is attached. It's ugly! I have experimented with alot of variables but still get this tearing of the metal instead of a clean cut.

    Machine: Tormach PCNC 1100 series 3
    Controller: PathPilot
    Tool: 1/2" Glanze through-coolant boring bar (steel)
    Insert: CCMT, tried one for steel and one for aluminum with the same result
    Surface speed: 150-500 meters/min
    Feed rate: 550-800 mm/min
    depth of cut: 0.25-0.5mm
    Insert is parallel to X-axis and centered in the bore

    All the other cuts on the machine are working great. Facing, turning, parting are all no problem. What am I doing wrong with boring?

  2. #2
    Neuer Benutzer
    Join Date
    Jan 2013
    Posts
    535

    Re: Boring 6061 - horrible surface finish!

    That's fairly aggressive I would think. Looks like it chattered a lot.

  3. #3
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    Nov 2003
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    284

    Re: Boring 6061 - horrible surface finish!

    Are you using the shortest boring bar possible? Just long enough to reach bottom of bore.

  4. #4
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    Aug 2015
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    Re: Boring 6061 - horrible surface finish!

    Quote Originally Posted by vertcnc View Post
    Are you using the shortest boring bar possible? Just long enough to reach bottom of bore.
    The hole is only 3/4" deep, The boring bar stickout is about 1.25" right now. If I eliminate the through-coolant, I could choke is up right next to 3/4".

    On my manual lathe, I can run a lot more stickout than that with no chatter. And that's with a cheaper, thinner boring bar.

  5. #5
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    Jun 2013
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    1002

    Re: Boring 6061 - horrible surface finish!

    Try again at 3-500 rpm 50-80mm per minute. I've not used the tormach but when I'm having trouble boring that range almost always works well.

    Ben

  6. #6
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    Aug 2015
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    10

    Re: Boring 6061 - horrible surface finish!

    Thanks for all the help and suggestions here. I finally fixed the problem by a combination of choking up on the boring bar as far as possible, re-routing the coolant line to maintain through-coolant, .25mm depth of cut, 157 m/min surface speed, and 550 mm/min feed rate.

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