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Carbide end mills, short life

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  • Carbide end mills, short life

    I've had my mill for some time now, an XLO. My question is about a lack of longevity with end mills. I'm using a mister for cooling and looking up feeds and speeds with FSWiard but seen to loose the edge off of end mills quickly. What am I doing wrong. My latest project is making an follow rest for my lathe, 1018 mild steel, 3/4" carbide 2 flute end mill running at 1000 rpm and .100" depth of cut, probably running at 1/2 to 3/4 of feed rate, three passes in and have lost the edge on the side of the end mill. The coolant is cool mist 77 I think. I am open for suggestions. Thanks

  • #2
    Are you slotting? Poor chip evacuation will do that. XLO looks to be a very stout machine so ruling that out unless you are using poor workholding methods allowing the part to flex or move.

    Sent from my SM-G950U1 using Tapatalk


    • #3
      Originally posted by quadrod View Post
      I've had my mill for some time now, an XLO. My question is about a lack of longevity with end mills. I'm using a mister for cooling

      1018 mild steel, 3/4" carbide 2 flute end mill running at 1000 rpm and .100" depth of cut, probably running at 1/2 to 3/4 of feed rate, three passes in and have lost the edge on the side of the end mill. The coolant is cool mist 77 I think. I am open for suggestions. Thanks
      I am only gonna trow a shot at it so... 3/4" or 3/8"? That is a massive chunk of carbide. In two flute. Prolly 3/8 assuming

      The two flute deal. Thats an aluminum bit. You really dont need to go esoteric with Carbide Endmills. Center cutting or not? Two or four flute.

      Try a four flute with center cutting, I like center cutting endmills, I wont buy the other stuff cause I am not a factory

      Oh!! And lay off the cooling for the carbide, you will fracture it.
      My old yahoo group. Bridgeport Mill Group


      • #4
        Climb milling or conventional milling?

        Chip re-cutting or chatter are most likely causes. Or excessive runout.
        Location: Helsinki, Finland, Europe


        • #5
          Originally posted by JRouche View Post
          The two flute deal. Thats an aluminum bit.
          No, not really. 2 flute is good for aluminum, but that doesn't make it "an aluminum bit". They're good for steel as well, and highly recommended over a 4 flute for slotting. He's not running a production shop obviously, so the additional feed rate capability of a 4 flute doesn't really matter.

          quadrod - are you taking a cut and then bringing the cutter back over the cut for the next pass so that it's just skimming the fresh cut? That can chip edges of carbide end mills; it's better to either step the part away from the cutter for the return pass, or take a shallow cut. Dwelling at the end of a cut can do the same thing. If you eliminate those two things, your carbide should last a lot longer.


          • #6
            Forget coolant with carbide cutters in steel.
            Cutting too slow is no good with carbide either. You want nice blue chips coming off the cutter. The blue color indicates that the cutting heat is being removed with the chip and not staying in the cutter. Sometimes being more aggressive with carbide is better.


            • #7
              Unless its only moderate cutting, I use coolant almost all the time with carbide inserts. It greatly extends the life of the insert and in some cases improves chip control. There is no danger of fracturing the cutter if the coolant is continuous, and started when the cutting starts.

              For the OP: I use a mist coolant system too, but I use relatively low air flow and 'sputter' the coolant unless higher air flow is needed for chip clearing. You didn't give specifics on the brand of endmill or your actual feed rate. Quality can make a huge difference in performance and durability. Personally, I'd slow a 3/4" 2-flute down to 800 rpm and try again.
              Southwest Utah


              • #8
                You will chip solid carbide cutters if you touch on to steel with the cutter stationary.


                • #9
                  3/4" 2 flute, first pass was a slotting pass, did 3 slotting passes for a depth of .300", then two side milling passes to widen slot. Brand in this case was kodiak cutting tools, no coatings, feed rate was may be 1 to 1 and a 1/2" a min. The mister I'm using is one I made my self, one tube inside and outer tube, air flows through inner tube, coolant flows through outer tube so it throws droplets onto cutter/work piece. A needle valve can adjust coolant flow.


                  • #10
                    Also I did not have a 4 flute cutter available this time, carbide is expensive.


                    • #11
                      Turn the mist off and just use the air blast to evacuate the chips from the cut.Like mentioned,re-cutting chips is the #1 way to lose cutting edges on solid carbide endmills.
                      Other suggestion would be to check your chips to verify chip load.Just mic them for thickness,should be .0015-.002" on a two flute 3/4 diameter endmill.

                      *IF* the chip load is correct and you are getting kind of twisted wide chips then everything is fine and it's probably just poor chip evacuation.

                      *IF* the chip load is correct and you are getting short needle like chips,then it might be time for some spindle bearings.

                      If all that checks out,then it could simply be the endmills you are using,maybe try a different brand or make sure the grade you are using is correct for the material.
                      I just need one more tool,just one!


                      • #12

                        My first thought is the mister. With carbide endmills, flood or nothing. If you want better chip evacuation, straight air with no coolant will be best.
                        If you think you understand what is going on, you haven't been paying attention.


                        • #13
                          Well, you've got a quality cutter and 'mist' is fine. I wonder sometimes if the naysayers for coolant on carbide have ever actually used it. The only reason I can think of is that they never really work the tool. With a good mister you can go high on the airflow for chip clearing if wanted, and whatever you need on coolant. I generally avoid fine 'mist' since it fills the shop and I don't like to run the evac blower when the air is on and its 108F outside.

                          I'm sure you'd get better results with a 4-flute, and where possible a roughing cutter is much easier to work with for both the machine and chip control. You should easily be able to cut .3 deep in one pass with a good rougher. Truth is, mild steel isn't the greatest to mill and I do see improved cutting with coated edges.

                          I use Rustlik WS5050 at 16:1 dilution and get great results on all carbon steels as well as 304SS and even aluminum. The only thing I don't use it for is tapping.
                          Last edited by chipmaker4130; 08-18-2019, 11:43 AM.
                          Southwest Utah


                          • #14
                            If I am reading this correctly, you are spinning an uncoated 2 flute endmill at 1000 rpm. You have a 100 thou depth of cut and an estimated .5 to 1 inches per minute feedrate.

                            By the estimated feedrate, I'm guessing that you are feeding by hand.


                            I think that both your depth of cut and feedrate are too low. Only engaging 100 thou of the endmill focuses the wear in that area. Engaging more of the flutes spreads the wear. You should be able to use half the diameter of the endmill as a starting point for depth of cut so in this case you could slot at full depth.

                            Hand feeding always seems to wear endmills faster, likely due to inconsistent feedrates. If you have an auto feed, I'd suggest using it. If not, I'd practice maintaining a consistent and faster feedrate. This is easier to do with a smaller endmill. If you have one I'd try a half inch endmill.

                            At .5 ipm your chipload is .00025, which is too low. You should be at least 4 times that. As another poster wrote, thicker chips remove heat from the part. So feeding faster both removes heat better and material faster.


                            Sent from my XT1710-02 using Tapatalk


                            • #15
                              Images and/or video would be very helpful. I've only used carbide tooling on my lathe, without problems. I've used cheap Harbor Freight HSS 2 flute end mills on my mill/drill, usually at low speed, feed, and DOC, with hand applied coolant/lube.

                              You might try an insert type milling cutter. A 16mm 2 flute cutter can be purchased for as little as $8:


                              Inserts are just $15 for a lot of 10, from the same company (others as cheap as $4/1):

                              Last edited by PStechPaul; 08-18-2019, 03:15 PM. Reason: Better quality inserts (MZG)
                              Paul , P S Technology, Inc. and MrTibbs
                              USA Maryland 21030