RPM query

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RPM query

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  • #714286
    Steve Huckins
    Participant
      @stevehuckins53362

      Can I get some advice about cutting speeds where my VM25 milling machine has a top RPM of 2250 approx.

      I have used the formulas to calculate for a 10mm HSS 2 flute end mill for cutting alluminium.

      Using 300 as the SFM the equation gives an RPM of 3048

      If I calculate for a 6mm end mill the result is 4559, a lot higher.

      Should I just accept that my maximum is 2250 RPM and use this where ever the need is higher ?

      I am trying to learn to get everything right according to the perceived wisdom.

      Regards

      Steve

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      #714288
      Oldiron
      Participant
        @oldiron

        Unfortunately that’s what most of us with older or smaller mills or lathes for that matter have to do.  Most times things work out fine. Just be careful and reduce the feed down for smaller size cutters or you will break them.

        regards

        #714290
        JasonB
        Moderator
          @jasonb

          Yep, if you can’t run at the calculated speed then just run at your maximum, You can then work out the feed based on the rpm and chip load

          #714307
          old mart
          Participant
            @oldmart

            A lot of those speeds and feeds are intended for industrial applications, so don’t worry too much about not being able to apply them exactly to your milling. Its best not to try too hard to fling swarf all around the workshop, concentrate in getting good results rather than how fast you can cut metal. Most work can be done at maximum rpm when cutting aluminium, listen to the motor sound and reduce the cut rate if it shows signs of struggling. A small ammount of lubricant such as WD40 or AC90 helps the cutting by stopping the aluminium sticking to the cutter, which is not good.

            The mills at the museum have top speeds of 3000 and 2400rpm which is common, wheras CNC mills reach 12000 or higher, with ten times the horsepower and flood coolant all the time.

            #714320
            David George 1
            Participant
              @davidgeorge1

              Hi Steve welcome to the forum. When cutting with High Speed Steel cutters it helps to reduce the speed of both the spindle speed and the feed rate and the cutters will last longer. Also use a lubricant which will help to cool and lubricate the cut which will improve finnish. For aluminium I use parafin which is cheep from B&Q, cutting oil or coolant made from a concentrate and water for steel or similar. For brass I dont use anything as it dosnt need any and the same for cast iron which I have a magnet in a plastic bag which attracts the swarf but take the magnet out over a bin and the dust and swarf falls off. Bronze is better with a touch of cutting oil. I have ocasionaly had to cut with a very small cutter and instead of running my little mill at high speed for a long time, which may burn out the motor i have a cheep high speed spindle mounted in a bracket which clamps around the mill spindle quill and can run up to 10,000 RPM.

              20220717_12202220230205_223041

              David

               

               

              #714328
              Diogenes
              Participant
                @diogenes

                Now his query has been ‘sorted’, I hope Steve won’t mind if I quickly ask what is it that you are doing there, David?

                #714354
                David George 1
                Participant
                  @davidgeorge1

                  Hi Dioganes.  I am engraving a tailstock quill with a scale to mark like a rule on the outside diamiter with a carbide 3mm shank pointed cutter.

                  David

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