cutting bar aluminum with mill

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • hwingo
    Senior Member
    • Sep 2007
    • 1442

    cutting bar aluminum with mill

    Hi Guys,

    My question involves getting a smooth surface when using an end mill to cut through a 1” piece of aluminum.

    I am starting with a piece of aluminum stock approx. 3 feet long x 2” wide x 1” thick. I want to cut off a section that’s 6” long. When the cut is complete, I want the end to be clean and very smooth. I placed the stock piece in a milling vise and tightened the jaws. Approximately 8” stuck out the side of the vice (just enough clearance for the quill). The piece sticking out was unsupported at its end. I used a ¼” carbide 4 flute end mill to make the cut using multiple passes (.015” per pass). Appropriate table and Z axis were locked each time as was the quill.

    When the piece had been cut, the end was not smooth. Under close inspection the end surface looked “wavy” (thought straight). Before taking the piece from the vise I decided to make another pass in hopes to get a far smoother end surface. Feeding slowly, taking a very fine cut from the end (.002”), I passed my cutter along the end surface making the .002” cut. The surface was still rough and without making the cut any deeper, I passed the cutter back and forth several times in attempts to smooth the surface. To some extent I realized a little better surface but not like what I would get if using a surface facing mill cutter.

    Is there a trick to getting the surface I desire using the above method and if so, what’s the trick? Am I expecting too much of the method indicated above?

    Thanks,
    Harold
    For those having fought for it, Freedom has a flavor the protected will never know.
    Freedom is only one generation away from extinction.
  • Evan
    Senior Member
    • May 2003
    • 41977

    #2
    A four flute end mill isn't the best for slotting. A two or three flute works better. If you need to use a four flute cut it long and surface it after.

    Also, the quality of a peripheral cut, especially in aluminum is very dependent on the helix angle of the flutes. For the best result you need a cutter with a fast twist.
    Last edited by Evan; 04-10-2008, 08:58 AM.
    Free software for calculating bolt circles and similar: Click Here

    Comment

    • torker
      Senior Member
      • Dec 2003
      • 6048

      #3
      That cut should be fairly clean. If I follow you right...you are cutting a groove to cut the piece off?
      Could be getting chip weld on the cutter.
      What rpm you running and what machine?
      What grade aluminum?
      Are you blowing the chips out as you mill it?
      If I could I might use a bigger, stiffer cutter...
      Russ
      I have tools I don't even know I own...

      Comment

      • hwingo
        Senior Member
        • Sep 2007
        • 1442

        #4
        Evan,

        Should I be able to "surface cut" using the side of a two flute in one pass without getting the "jiggleys"? Should I use a larger dia two flute cutter?

        Harold
        For those having fought for it, Freedom has a flavor the protected will never know.
        Freedom is only one generation away from extinction.

        Comment

        • torker
          Senior Member
          • Dec 2003
          • 6048

          #5
          My experience.. 2 flute endmills aren't very stiff. Not really meant for sidemilling. I'd try that finish cut in one pass with a 1/2" endmill.
          Last edited by torker; 04-10-2008, 09:11 AM.
          I have tools I don't even know I own...

          Comment

          • hwingo
            Senior Member
            • Sep 2007
            • 1442

            #6
            Originally posted by torker
            That cut should be fairly clean. If I follow you right...you are cutting a groove to cut the piece off?
            Could be getting chip weld on the cutter.
            What rpm you running and what machine?
            What grade aluminum?
            Are you blowing the chips out as you mill it?
            If I could I might use a bigger, stiffer cutter...
            Russ
            Yes I am cutting a groove to cut the piece off.

            I am running at 1600 RPM and using Industrial Hobbies mill.

            Using 6061 aluminum.

            I vacuum out the chips with each pass but not until the pass is complete. I rarely use compressed air to clear chips. I do use cutting fluid but it's not a constant flow.

            Harold
            For those having fought for it, Freedom has a flavor the protected will never know.
            Freedom is only one generation away from extinction.

            Comment

            • torker
              Senior Member
              • Dec 2003
              • 6048

              #7
              Harold...you gotta keep the chips out as you mill the groove. Can you turn the coolant flow up?
              I have tools I don't even know I own...

              Comment

              • hwingo
                Senior Member
                • Sep 2007
                • 1442

                #8
                Originally posted by torker
                Harold...you gotta keep the chips out as you mill the groove. Can you turn the coolant flow up?
                I do not have a constant flow device for the mill. I flood the area with cutting fluid each time I begin a pass and vacuum after each pass. This may explain why I am getting the "jiggleys" when cutting a goove but chip clearance should not be an issue once the piece has been cut off and a final surface cut is taken since chips should fall away freely ..... or am I wrong with that thinking?

                Harold
                For those having fought for it, Freedom has a flavor the protected will never know.
                Freedom is only one generation away from extinction.

                Comment

                • japcas
                  Senior Member
                  • Nov 2004
                  • 1149

                  #9
                  Harold, side milling with the edge of the endmill will never give as good a finish as a facing cut will. That doesn't mean that you can't get a nice finish though. Have you tried climb milling on the finish pass? Take about .003 to
                  .005 and climb mill your finish pass with a slow feed rate and you should get a better finish. Also, you might want to step up to a bigger cutter so there will be less flex during the cut.

                  Edited to say: I have a similar mill from Penn Tool and there shouldn't be any problems with climb milling on that small of depth of cut. I do it all the time and usually get decent finishes.
                  Last edited by japcas; 04-10-2008, 09:28 AM.
                  Jonathan P.

                  Comment

                  • hwingo
                    Senior Member
                    • Sep 2007
                    • 1442

                    #10
                    Originally posted by japcas
                    Harold, side milling with the edge of the endmill will never give as good a finish as a facing cut will. That doesn't mean that you can't get a nice finish though. Have you tried climb milling on the finish pass? Take about .003 to
                    .005 and climb mill your finish pass with a slow feed rate and you should get a better finish. Also, you might want to step up to a bigger cutter so there will be less flex during the cut.

                    Edited to say: I have a similar mill from Penn Tool and there shouldn't be any problems with climb milling on that small of depth of cut. I do it all the time and usually get decent finishes.
                    Hi Jonathan,

                    I have no idea about "climb milling". Could you explain this please.
                    Harold
                    For those having fought for it, Freedom has a flavor the protected will never know.
                    Freedom is only one generation away from extinction.

                    Comment

                    • japcas
                      Senior Member
                      • Nov 2004
                      • 1149

                      #11
                      Harold, climb milling is when you feed the work in the same direction the cutter is rotating. Conventional milling is when you feed the work against the cutter rotation. On a manual mill, you should only climb mill on a finish pass with a minimum of material removal. You should be able to do the full 1 inch depth but feed the cutter into the part only about .003 to .005. When climb milling, if you try to take to much material off at once, the cutter will try to pull the work into it which can break the endmill. This is because of the slack in the feedscrew and it's nut. Conventional milling keeps pressure on the nut and feed screw so everything works as it should. It's harder to explain in words than it really is. But it's just a basic machining principal.
                      Jonathan P.

                      Comment

                      • Evan
                        Senior Member
                        • May 2003
                        • 41977

                        #12
                        Free software for calculating bolt circles and similar: Click Here

                        Comment

                        • smiller6912
                          Senior Member
                          • Jan 2008
                          • 447

                          #13
                          Here this may help some............
                          "Those who hammer their guns into plows will plow for those who do not."~ Thomas Jefferson

                          Comment

                          • snowman
                            Senior Member
                            • Mar 2004
                            • 2057

                            #14

                            Comment

                            • mechanicalmagic
                              Senior Member
                              • Oct 2007
                              • 441

                              #15
                              I believe a 1/4" diameter end mill is not rigid enough for a 1" deep cut.
                              That's four diameters deep, I try to keep it to three.

                              Especially if it is not super sharp.

                              I suggest a SHARP 1/2" diameter, and climb milling.

                              Comment

                              Working...
                              X