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What speed for indexable mil?

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  • What speed for indexable mil?

    I got this bit for Christmas I have a solid carbide 3/8" 4 flute bit , just playing around at 2700 rpm with flood coolant, and it's a blast. It blows through metal. Are the insert bits the same speed as a solid bit other than the flute number? I've wanted one to play with and my brother bought me this one as a present. I don't want destroy it. My old mills max rpm is 2700. I don't know if the calculations for indexable bits are different from solid ones.

  • #2
    At 2700 rpm your cutter is whizzing by at 353 surface feet per minute. I aluminum, that's about 1/4th the speed it's capable of doing. In a hardened steel, that's about twice the rate you should start at. In a typical 1018 steel, it may be just about right.

    So you see, there's no one answer. It all depends upon the carbide grade, coating, and geometry, then you factor in what material you're cutting and how it cuts with the given carbide.

    What inserts did you get for the cutter? What materials do you wish to cut, and what type of operation would you like to do? As it related to the solid carbide 4-flute end mill you describe, the main differences are: The end mill can run 4x the feed rate (in inches per minute) as the single edge cutter. It also enjoys a higher shear angle because of the way the flutes are ground, so you have less cutting force with the end mill.

    How you run the little indexable cutter depends upon what you have and what you wish to do.


    • #3
      I run them at about 1000 rpm. For every thing . Always have they work good.
      Every Mans Work Is A Portrait of Him Self


      • #4
        Straight up and down insert holders like that tend to slap or hammer the work. If it sounds loud that is why. The inserts are the biggest portion of knowing what speed to run. Watch the surface you are cutting for feedback. Don't know what mill you have but make sure everything is tight. A lot of play can kill carbide inserts faster than you can blink. If you are running CNC you have to calculate for one flute instead of four (i.e. feed per tooth).