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  • Flutes

    Hey folks,

    Can someone help with the difference between 2 or 4 flutes on end mills? Also is there speed and feed differences between them?


  • #2
    I'm no expert, but I use 2 flutes for roughing, 4 flutes for finishing, and 3 flutes for slotting. Since all my milling is done in a lathe, I listen to the lathe tell me about speeds and feeds. Sorry I cannot be of more help.


    • #3
      Basically, the more flutes, the less room for chips, but smoother cutting. It's a compromise. If you're doing deeper slots where chips can't escape as easily, use the 2 flute. If you're cutting a lip around the outside of a cover, for instance, use a 4 flute. An idea is to keep at least 2 cutting edges in contact with the material if possible, to reduce chatter. The cutting speed for each flute won't change with the change from 2 to 4 flute, but the depth of cut per tooth will, and so will the power req'd to turn the endmill, as will the deflection of the endmill increase. As stated above, pay attention to the sounds produced, and learn to judge feed accordingly. Sometimes it's a good idea to get an experineced machinist to work your machine, and give you guidelines based on his knowledge of sounds produced during machining. The limitations of your machine will show up in the noise and surface finish, and you'll get a better idea of how fast you can feed, and how deep of cuts you can take.

      [This message has been edited by darryl (edited 04-10-2003).]
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


      • #4
        Same rpm for 2, 3, and 4 flute endmills (function of sfm and diameter). In principle the feedrate of 4 flute should be twice that of 2 flute, but in practice you can't go quite that fast (function of rigidity, hp of motor, rate of chip removal, helix angle, etc).

        As other have noted, listen and feel the machine and it will tell you when to back off.

        2 flute is also much better suited for doing plunge cutting.



        • #5
          I use two flute for soft material like aluminum and four for steel and stainless,but this is no hard and fast rule.I have also noticed that two flutes are better on slots with bottoms in them i.e/keyways,they seen to have an easier time with chip build up than the four flute models.also four flutes can double as an acurate reamer for shollow holes once the bulk of the material has been removed with a drill bit.
          I just need one more tool,just one!


          • #6
            Ironicly, the two flutes often give a better finish because the are mere rigid than a four flute. Two flute cutters are easier to sharpen and are almost always center cutting. Four flute mills can be center cutting or non center cutting.


            • #7
              Thanks everyone for your replies. I guess ust more practice is what i need. Gets expensive buying end mill all the time but i am slowly figureing all of this out.

              I bought a face mill. 3 carbide, 2`` wide. I am not having any success with it though. should shallow cuts be taken with this kind of cutter?



              • #8
                Spkrman, what did you buy, a known good face cutter, or something dubious? I'd check for proper cutting edges, maybe the thing is inferior right out of the box. I was able to make acceptable cuts right away with mine, before I knew much about milling, so I'm kind of doubting the cutter. If your machine is rigid, including the mounting of the workpiece, you should be able to take cuts deep enough to load the motor noticeably, without milling a poor surface, or causing horrible noises. Pay attention to any part of the machine where play is evident, and apply appropriate measures.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                • #9
                  You can have problems with facemills for a variety of reasons. Insert geometry is the most important. With a 3 insert facemill you would be advised to use highly positive inserts to minimise cutting forces - thus reducing HP requirements. Learn how to calculate the feed per tooth of endmills and face mills and adjust feedrates to insure a minimum of .oo3" per tooth for stainless steels to get under the work hardened layer. Softer materials you can push the speed (Aluminum, brass, bronze) - listen to the machine.

                  There are single flute endmills, but these are normally used in high speed spindles for wood, Aluminum, and graphite - they are sometimes called "routers" instead of endmills. In general, a 4 flute will give a better finish and is best used on machines with ball screws to ensure control when feeding with the direction of rotation (down milling versus traditional milling where the work is fed against cutter rotation) - woodworkers call this the "hungry way" as it has a tendency to pull the work into the cutter - a bad thing with a router! This produces a better cut because the endmill takes a big bite into the work at the start of the cut and the chip thins out at the exit of the cutting edge - this take more horsepowe, but has the added advantage that the chip tends to be thrown out of the cut where as in conventional milling there is a marked tendency to pull the chip back around with the endmill and cut the chip again - a bad thing. Three flute endmills were developed for the high speed cutting of Aluminum - a comprimise in quality of finish for the higher strength of 1 less flute than a 4 flute. More flutes = weaker endmill.

                  There is no free lunch. Minimise cutting edges to increase available HP. Doing so reduces surface finish quality. But remember there are no rules carved in stone. In general we avoid overhang to ruduce chatter - however, it has been recently shown that tuning overhang to system frequencies can ENHANCE cut quality. In effect they find a "sweet spot" and use it to their advantage and this can dramaticaly increase metal removal rates sometimes. The more we learn, the more we change how we use the tools available to us - increasing their usefulness.