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Thread: More boring tooling...

  1. #11
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    What I would do with that now is remove the insert and give everything a good clean. Then coat the insert with an anti-friction spray like Top-Cote. Fill the cavity with JB Weld and carefully place the insert, making sure that any JB that enters the threaded area gets removed. Install the bolt snugly but not tightly at this point, and clean up the rest of the JB. I'd leave it for a couple days before using it again to let the JB get really hard. Then fully tighten the bolt.

    Chances are that the insert will free itself from the epoxy during its first use, so you won't have to worry about prying it out when you want to change it.

    This will give the best support for the insert that you can give it at this point.

    One thing I wonder about is whether this is the right insert for the job- perhaps there one which will work better here. I'm quite fond of very sharp tooling- perhaps a high grade HSS insert would be better for boring work.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  2. #12
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    Quote Originally Posted by millwrong View Post
    If you examine how far back from the insert pocket you have relieved, I think you've made a mini-diving board! Notice on commercial boring bars that the relief stops right after the insert pocket. Think maximum rigidity. JMTC.
    Probably not issue if you think of diameter/thickness still left. Less relief could be worse or could be better depending on your luck how the various resonance frequencies match up.

    Lots of things can make 5xD boring bar unhappy.

  3. #13
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    Found this boring picture by accident:


  4. #14
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    Quote Originally Posted by MattiJ View Post
    Probably not issue if you think of diameter/thickness still left. Less relief could be worse or could be better depending on your luck how the various resonance frequencies match up.

    Lots of things can make 5xD boring bar unhappy.
    I can agree with your statement that,"Lots of things can make 5xD boring bar unhappy.", however stiffness is directly proportional to cross-sectional area. Perhaps if your bar has a high young's modulus,e.g. made from diamond, you might not worry so much about cross sectional area. This is why carbide bars are ubiquitous-high stiffness.

  5. #15
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    Quote Originally Posted by MattiJ View Post
    Found this boring picture by accident:

    Now thats boring!

  6. #16
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    Jul 2014
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    Southern Indiana
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    The picture posted by MattiJ reminds me of my younger days. Thanks for posting it.

    Sarge41

  7. #17
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    May 2015
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    If you are boring a taper, the tip must be on the centre line, otherwise a tad high. Keep an eye out for a Densimet bar, it can be milled and threaded and would be better than steel. Those inserts should be horizontal in the toolholder, and the seating milled to get the height, not dipped down.
    Last edited by old mart; 08-17-2019 at 04:56 PM.

  8. #18
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    Quote Originally Posted by old mart View Post
    Those inserts should be horizontal in the toolholder, and the seating milled to get the height, not dipped down.
    Looked like DC?MT11T3 size insert that has 7? degree relief angle and it is 5/32" or abouts 4mm thick.
    If you set it horizontal and centerline without giving extra relief it needs ~65mm bore not to rub on the insert "heel" (if my rough math is anywhere correct.)

    DPMT is another common insert of same size but with 11 degree relief angle and would work from minimum dia of 44mm or so without extra tilt.

  9. #19
    Join Date
    Dec 2008
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    Yeah, I had to grind some more relief off the nose of the insert for clearance. If I tilted the insert DOWN I wouldn't have had to. I'm going to try and find some time to remake this, properly, with the insert situated in the correct orientation.

  10. #20
    Join Date
    Apr 2012
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    Quote Originally Posted by MattiJ View Post
    Found this boring picture by accident:

    Is that a Myford?

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