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I think I'm finding the limits of my mill...

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  • I think I'm finding the limits of my mill...

    Last night I was milling the sides of a hexagon in 3/4" 6061 bar, rough cut to 1/16" - 1/8" of nominal size, by taking 1/8" deep passes along the sides. I've been slowly increasing my cuts, trying to figure out the limits of this little mill. I think I found one...

    I've cut all the way around the hexagon, and am working on the last side. This is one of the rougher sides, so I'm cutting a good 1/8" x 1/8" per pass. The mill is vibrating a fair bit, but it is cutting fine. Chugga chugga chugga. Getting down towards the bottom I notice the cut is getting rougher and rougher. When I finish, I reach up to turn off the mill, and notice that the head is tilted to the left about 5-10 degrees. I guess all the vibrating worked the bolt at the bottom of the column just loose enough for the side pressure to push the head over.

    I'm learning all the time, here...

    This does make me think I need a better end mill - I imagine I could cut more aggressively with a sharper mill, without working the machine so hard. Since I seem to almost always use a 1/2" mill, and generally work in aluminum, I'm thinking about this one. Any advice?

    -Pete
    I just like to make stuff.

  • #2
    search this part number 2716A31 at mcmastercarr, its a 3 flute endmill made for aluminum. mcmaster doesn't tell you what brand they are sending you, but they never send you junk, the last ones I got were made by Cleveland

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    • #3
      Originally posted by Pete F
      trying to figure out the limits of this little mill.
      What little mill ?

      This does make me think I need a better end mill
      Try a roughing mill, and maybe a smaller diameter. Perhaps 1/4" or so. Hard to say without knowing what kind of machine you have.

      On wimpy mills, never use a standard end mill when a roughing mill will suffice. Soooo much easier on the machine.

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      • #4
        For steel...you should try a rougher.
        They can make a small machine cut like a monster.
        Russ
        I have tools I don't even know I own...

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        • #5
          I use this one from an Ebay dealer with good success (or luck LOL)

          http://cgi.ebay.ca/1-2-3FL-USA-Harmo...item5ad58d0cca
          Ernie (VE7ERN)

          May the wind be always at your back

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          • #6
            Hammering it

            The machine is telling you that you are hammering the $hit out of it.

            Learn to "listen to" and to "feel" (for) your machine. Its not hard to do and will pay handsome dividends in terms of machine and tool use and life.

            Also make sure that the cutter is sharp and is not over-loaded in terms of cutting speed and cutting load.

            Make sure that the set-up is as rigid as you can get it.

            I thoroughly support the recommended "roughing" cutters. Use them in a conventional milling set-up for most material removal. The finish is not too bad either.

            For final/finishing cuts use a conventional cutter (preferred) or a "rougher" with a light cut but climb mill it.

            Read this:
            http://en.wikipedia.org/wiki/Milling..._climb_milling

            from:
            http://en.wikipedia.org/wiki/Milling_cutter

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            • #7
              Thanks for the feedback. I will look into roughing mills, and the 3 flutes that were suggested. I did not even consider carbide, because I thought that was generally for harder metals. Apparently not, I see.

              The mill is a harbor freight 44991 (Seig X2, right?). I do see that I was over-working the machine, but I wanted to push a little bit, and see what the limits are. Backing off a little bit on the cut does calm things down quite a lot, and I'm starting to get the feel of the transition. One reason I think I will be able to cut more (or more cleanly) with a better mill (roughing or otherwise) is that I'm using a mill from a $17 set of six, so it is pretty cheap. I got the set because I wanted to test the waters and try to learn a bit before investing in better tooling. I have read that it is a good idea to hold the mill and collet with a rag when putting it in the spindle. With this set, not so much of a concern - they're not that sharp. They do the basic job, though. Seems like a good starting point.

              About the mini-mill. I'm finding I'm actually glad to be learning on this. Not that I had a huge choice, mind you, it was the only option within reach. However, I find it is teaching me a lot, and I have a feeling I would be getting myself in trouble with a larger machine.

              Thanks again for the advice and support!

              -Pete
              I just like to make stuff.

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              • #8
                Originally posted by MTNGUN
                Try a roughing mill, and maybe a smaller diameter. Perhaps 1/4" or so.
                A question: I had thought it was better to use a larger mill when side milling, if possible, because there is less flex? Is it side milling when I'm cutting a 1/8" x 1/8" step, repeatedly down a side? In any case, I am going to definitely look into roughing mills.

                -Pete
                I just like to make stuff.

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                • #9
                  Heheh pushing it sure is fun. till it bites you back anyway.
                  One thing you might notice is above a certen feed rate, feed pressure goes WAY up while a tooth is cutting, this can be because you are actualy pushing the tool forward enough to make the relief on the teeth rub against the work.

                  Carbide lets you go even faster in aluminum, stupidly fast!
                  Apparently some aluminum alloys are actualy considered abrasive.. I like to live in lala land and try to ignore this but they are likey right, making carbide a good choice for roughing masses of aluminum, even if a fresh HSS could remove more on your machine (due to being sharper initialy), the carbide may be the way to go for roughing.

                  Also note don't use 'aluminum' designed endmills on steel, they typicaly are not designed to handle that kinda force and have a much more fragile sharp cutting edge.

                  For some reason, 3 flute endmills are 'raved' about for aluminum. I bought one myself and it seems to do nicely.. would'nt exactly write home about it but what do I know iv barly touched endmills. (except accidently.. many many times accidently.... *wipes some blood off the mill*)
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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