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Sharpening End Mills........???

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  • Sharpening End Mills........???

    The past few days I've been sharpening my cutters. I've noticed more closely that there are several different methods of gashing the end mill between the flutes. The cutters with a pilot hole generally aren't a problem with clearance but the center cutting ones are, especially after they have been sharpened a few times. I usually jut X the centers if needed with a Dremel, crude as it is, but some of these end mills have an under cut gash. Wondering what some of you guys do in these various situations.

    JL........................





  • #2
    The one in the bottom picture is how I do them. The main thing I try to do is keep a straight or nearly straight line on the end where it goes from the flute part to the center. If there is much of a step where the flute is dished out, then a straight part to the center, the step will be higher than the outer edge. I think you are doing fine.
    Kansas City area

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    • #3
      The picture on the bottom is a factory ground, I didn't cut the gash, just touched up the cutting edge. The problem is when it does come time to recut the gash it can't be done on the surface grinder with that fixture or wheel. I'm going to have to use a cup wheel like an 11v9 or something similar to do that and will have to come up with a way to hold the end mill at the correct angle. Sounds like a job for the T&C grinder.

      JL............................

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      • #4
        Hi,

        This is why grinding the ends is such a pain in the backside. On the upside though. Unless you are plunging over half the cutter diameter through solid, the gash isn't all that super critical. Almost all cutting is done on the periphery with no material contact on the inside. So I don't sweat it very much. When I do gash an endmill, I often just use a die grinder or even the edge of a belt grinder to give a bit of relief. It's fast, easy and all that's really needed.

        dalee
        If you think you understand what is going on, you haven't been paying attention.

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        • #5
          I made up a little fixture to hold my Dremel tool in center with my Spindex. I put a small grinding stone in the Dremel and spin the end mill in the spindex. You can put a little dimple in the center of the end mill that almost looks factory and can get them back to something like # 3 in your top picture.

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          • #6
            I am in the midst of learning how to use my little tool & cutter grinder, and tonight was end mill sharpening night.
            The worst of the mills had to be cut off square to get rid of a broken tooth, and after regrinding I gashed it on the edge of a cup wheel *carefully* by hand.
            I did not take a picture, but it turned out fine if a bit uneven.

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            • #7
              If using a CNC machine, then the center cutting feature is less important, as you can usually plunge in with a ramp. Just needs the center portion relieved.

              But yeah, I've used a 11V9 (I think) wheel to do those cuts, mostly freehanding the relieves but sometimes used a fixture when the accuracy has been important.
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                Shouldn't the secondary relief grind create the center gash? I know that's the case on most of my center cutting slot drills - one flute is ground longer than the other, then the secondary relief if ground on evenly, creating a gash in the longer flute end while still leaving it center cutting.

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                • #9
                  I grind mine on the surface grinder and do like Sun God says. I dressed a thin wheel to do the gash with the fixture on the secondary relief setting.
                  Kansas City area

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                  • #10
                    I cut the gash in this one this morning with my Dremel. I just followed the original gash angle, it's a little ratty on the top edge but it'll work just fine. I'm going to have to come up with a fixture to hold these on the T&C grinder and use the 11V9 wheel if I want to be more accurate. With an adjustable fixture I would then be able to cut all three angles on the same machine elim inating the second op.

                    JL....................

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                    • #11
                      Here is a photo (not that great) of an end mill sharpening chart that might be of interest.



                      Steve

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                      • #12
                        No, the gash is cut at a different angle than the secondary relief. However if you cut the secondary with an 11V9 wheel you could under cut the adjacent flute and give clearance that way. I would have to try one and see what happens. There are a few different ways.

                        JL....................
                        Originally posted by Sun God View Post
                        Shouldn't the secondary relief grind create the center gash? I know that's the case on most of my center cutting slot drills - one flute is ground longer than the other, then the secondary relief if ground on evenly, creating a gash in the longer flute end while still leaving it center cutting.

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                        • #13
                          Thanks for that chart Steve.

                          I recently sharpened the end flutes of a "high-helix" 7/8" end mill and got tied up in knots getting the gashing slice correct. Ended up having the cutting edge behind the center line. This was for a friend but the funny thing was that he found it worked far better (and lasted longer) than it did "as received". It was so long (7") that I had to use a drill sharpening fixture I made for my home made T&C grinder. Luckily it was only a two flute.

                          Geoff

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                          • #14
                            That's a nice chart. It doesn't mention anything about the gash. But what I find interesting is the difference in relief angles in relation to the diameters. I wasn't aware of that and since my fixture is set, (non adjustable) and is capable of sharpening end mills of all sizes I never gave it a thought that it mattered. Also what is interesting is the reference at the bottom where the relief varies for milling different materials.

                            JL.................
                            Originally posted by doctor demo View Post
                            Here is a photo (not that great) of an end mill sharpening chart that might be of interest.



                            Steve

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                            • #15
                              I have just started playing around with the same kind of fixture. I tried to hold my endmill the way shown in the start of this post. I got a square section in the middle of the endmill. I tried turning the EM about 89 degrees by MK#1 eyeball and ground the EM and it came out like the first picture. the web could use thinning. The second picture shows the center relief. It measures about .025 deep on a 9/16" endmill. Does this seem excessive? Would it hold up?
                              http://s558.photobucket.com/user/mco...tml?sort=3&o=1
                              http://s558.photobucket.com/user/mco...tml?sort=3&o=0
                              Last edited by Mcostello; 02-03-2014, 09:52 PM. Reason: screwed up pictures
                              mark costello-Low speed steel

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