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Defection question

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  • Defection question

    Thanks to those who replied to my cut-off tool holder and backlash questions, I've got another.

    I have an idea about this one, but want to ask folks who actually DO know.

    I regards to tool deflection, what would be better...keeping the quill up in the head, and using the end of an endmill to do the cutting, or to bring the quill out more and cut with the portion of the endmill closer to the shank?

    Say I had a work piece in the vise that I was going to plunge through, then cut a slot in, would I be better off plunging in deep and using the proximal end of the cutter thereby sending the quill further out of the head......or using the distal end of the cutter while keeping the quill further up in the head?

    Maybe I'm chasing ghosts, or it's a case of "six of one, half dozen of the other", but I don't have any formal training to go on, so I place myself in your capable hands.

    Thank you,


  • #2
    I was always taught to keep the quill up in the head as far as possible. Makes for a more rigid set up. As a rule of thumb, keep all of your set ups on anything that you are running close. I.E.-cutting tools and their holders, parts held in a vise or chuck. The further that you have something hanging out from where it is being held the more problems you will have. Deflection, vibration etc. Good luck, Smitty
    Smitty.... Ride Hard, Die Fast


    • #3
      If the end mill is over about .25 diameter, and standard length, it shouldn't make much difference...I would keep the quill up.
      If the end mill is a very small diameter, I would lower the quill and use the endmill as close to it's larger shank diameter as possible...should help reduce end mill breakage.
      If the end mill is extra long but only getting used for a short length, I would again lower the quill. The quill will flex less that the end mill. No sense in using a long end mill unless you need it though.
      Big Dipper


      • #4
        If you are worried about the cut being parallel, and do not want to take a spring cut to clean up the work area due to deflection,you can order your end mills with a negative taper grind. I was taught that most all end mills will deflect to some degree in all but the lightest of cuts. This deflection changes in proprtion to the diameter of the end mill, the depth of the cut, feed & speed, how sharp the tool still is, and the ridgity of the whole set up. To avoid taking spring cuts we used to rough out the cut and then change to a finish cut with a negative taper grind cutter. This way as the end pushes out of the cut, the end mill actually is cutting straight up and down as opposed to couple of degrees of taper from top to bottom. It may seem like a lot of work, but, if you are doing more than a couple of pieces and the have to be parallel, this saves time.And as we all know "Time is Money" or "better spent doing other things". Hope this helps.


        • #5
          Okay,lets assume that you have the quill out lets say 6" or about max.what is taking place?On a b-port type mill that means you still have 6" of quill up in the head,so unless you are using a big(1")endmill you won't have any problems with rigidity so long as you lock the quill.

          As for the plunge and slot,you have two choices,either plunge with the quill and keep the knee locked,or lock the quill and crank the knee up.If you use the quill it will believe it or not be more rigid than cranking the knee up.

          One thing I found that works on plunge cutting slots is to first center drill and drill a hole almost the same diameter as the slot is wide,then plunge your endmill in and mill your slot,this will greatly reduce the chance of ending up with a "keyhole"shaped slot.
          I just need one more tool,just one!


          • #6
            Quill up in all the way and locked. I do at times extend to a max of 2" on the quill, but by habit, keep it in tight unless needed otherwise.

            I keep this "habit" for all end mills 1/16 on up. Good habits are formed and used always with very few exceptions but for when needed by necessity, not "jiust 'cause'.

            Learnt this in my apprenticeship, and re-inforced by many a toolmaker I work with now.
            CCBW, MAH