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  • dry machining aluminum...??

    I've been playing around w/ aluminum lately trying to figure out the best way to drill a precision hole on a milling machine through 2 pieces (.75" ea. or 1.5" inches total thickness) of 2024 aluminum. Is there a proper way to dry machine aluminum. It seems that I get most of the way through and need to pull out to get rid of the chips. Id like to be able to drill to total depth w/ out pulling out of the hole. Is this posible when dry machining...What kind of RPM should I be drilling at...(1/4" - 9/32" hole size).....What about the feed rate. When the RPM was at 2000 the 2 flute bit packed w/ chips. Should I be looking at a different type of bit. I'm a rookie when drilling aluminum..

    Thanks for the help in advance. ......................Krems

  • #2
    Dry machining works well if you have chip clearance. If not then you need to use some lube and clear the chips regularly. Keep in mind that when drilling deep holes the chips have nowhere to go if the top of the flutes are buried in the hole.
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    • #3
      Slow the speed down to about 500- 600 rpm and use lots of coolant or TapMagic ect. Being a newby I would also peck at it........ as in drill a little back out....drill a little back out , no drill can go it's entire depth with out backing out to clear it's flutes.

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      • #4
        Originally posted by krems
        I've been playing around w/ aluminum lately trying to figure out the best way to drill a precision hole on a milling machine through 2 pieces (.75" ea. or 1.5" inches total thickness) of 2024 aluminum. Is there a proper way to dry machine aluminum. It seems that I get most of the way through and need to pull out to get rid of the chips. Id like to be able to drill to total depth w/ out pulling out of the hole. Is this posible when dry machining...What kind of RPM should I be drilling at...(1/4" - 9/32" hole size).....What about the feed rate. When the RPM was at 2000 the 2 flute bit packed w/ chips. Should I be looking at a different type of bit. I'm a rookie when drilling aluminum..

        Thanks for the help in advance. ......................Krems
        2024 is soft and gummy, with a new sharp drill you could probably get away with one hole before the drill would start loading up and gettiing sticky, you dont need to flood it with coolant though, try either spraying it with wd-40, or apply kerosene with a small brush to the drill bit. A peck of about 1/4" will probably be best unless you get a parabolic style drill,

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        • #5
          Originally posted by Renegade
          Slow the speed down to about 500- 600 rpm and use lots of coolant or TapMagic ect. Being a newby I would also peck at it........ as in drill a little back out....drill a little back out , no drill can go it's entire depth with out backing out to clear it's flutes.
          Gun drills can, they blow out the chips with threw the bit coolant.

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          • #6
            I'd say you got pretty far in before the chips packed. Probably too much to ask to get it through in one go.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              Originally posted by mochinist
              Gun drills can, they blow out the chips with threw the bit coolant.
              Homer Simpson quote.........Doh.
              How many people do you know that use a 1/4 inch gun drill to put holes in 1-1/2 inch thick Aluminum using a mill or a drill press?

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              • #8
                Originally posted by krems
                Should I be looking at a different type of bit.
                Try a parabolic flute drill. Some are advertised to go 10 times diameter with no pullout to clear chips. Get one with polished flutes.

                What's your problem with having to pull out to clear chips? That's the way it's done in production.

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                • #9
                  I'm always looking for a more efficient way to get a job done. I don't have a problem pulling out to clear the chips. I would rather not if I could get away with it. I watched a video somewhere where the machine was drilling holes an inch deep w/ out lubricant and drilling to depth w/ out pulling out. I really don't want to be using lubricant on Aluminum if I can get away with it.

                  Looking at my drill bits I probably don't have enough chip clearance as compared to a parabolic bit. I am able to peck drill my way through w/ good results. I'll pick up another bit and give it one last try. I'll probably end up peck drilling w/ out lubricant.

                  Thanks!............Krems

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                  • #10
                    Originally posted by J.Ramsey
                    Homer Simpson quote.........Doh.
                    How many people do you know that use a 1/4 inch gun drill to put holes in 1-1/2 inch thick Aluminum using a mill or a drill press?
                    Your reading to much into it, I'm not suggesting to use a gun drill for this job, I was just debating what renegade said. "no drill can go it's entire depth with out backing out to clear it's flutes."


                    doh

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                    • #11
                      Just use a little WD-40. Pull it out often to clear the chips. If you are careful, you will be using the same drill years from now.

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                      • #12
                        A gundrill won't run dry for more than a very short distance, and drilling a hole in a plate like that would be interesting with the coolant coming out at 300+ psi it would have to have a complete enclosure. It is an interesting thought experiment though, but I think he asked about drilling dry which kind of excludes gundrills.

                        -brian
                        -brian

                        Hello, my name is brian and I'm a toolaholic.

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                        • #13
                          Is there any particular reason you want to drill aluminum dry?

                          You say that you are looking for a more efficient way to get a job done but drilling 2024 aluminum dry is false economy IMHO.
                          To do that will require you to slow down the RPM and the feed. Even then 2024 is so gummy that it won't take long for the chips to glue themselves to your drill bit. When that happens, you will have to stop and clean it or change drills. It will also leave the finish inside the hole very rough and messy!

                          These are the reasons why you see CNC machines shooting huge volumes of coolant on the parts and cutting tools. It's simply a matter of removing the greatest amount of metal in the least amount of time, i.e. Efficiency.

                          Squirt a little WD-40 or a good aluminum cutting fluid on it and be done with it.

                          Regards,
                          Greg
                          "The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is." Winston Churchill

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                          • #14
                            2024 isn't gummy unless it's in the annealed condition. 2024 is aircraft alloy and is very high strength, nearly as strong as 7075. In the T3, T4 or T6 tempers which is how it is usually supplied it drills clean and crisp with almost no burr. Like 7075 it has a tendency on a deep hole to grab the bit so coolant helps a lot. Because the chips are hard they will jam and score the hole causing problems. It has the same tensile strength as mild steel and only 5% elongation at break.

                            It is usually drilled dry when drilling holes in thin material such as aircraft skins but coolant is recommended on deep holes.
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                            • #15
                              I stand corrected on the gumminess of 2024 but I still stand behind my comments on using a lubricant.
                              "The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is." Winston Churchill

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