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Perforating 2" OD, .065 wall 6061-T6 tubing... Best method?

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  • Perforating 2" OD, .065 wall 6061-T6 tubing... Best method?

    I've already got it secured in Vee blocks nice and rigid. I've got to put roughly 36 holes in around the circumference and length, largest holes being 3/8".

    Should I:

    a) plunge with a center cutting endmill
    b) spot drill, drill a small pilot hole, then plunge with the endmill
    c) spot drill, drill with a small pilot hole, finish with a 3/8" drill
    d) spot drill, drill through with a 3/8" drill
    e) just be a man and use the 3/8" drill (i'm afraid of walking)

    "a" makes the most sense to me, but I'm wondering if the endmill will grab when breaking through and do naughty things.....

    Willing to consider an "f" if there is a better way. All I've got is a rockwell mill and a clausing lathe....

  • #2
    Center drill all your holes and use a step drill.
    Duffy, Gatineau, Quebec

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    • #3
      Hmm... good idea. Really good idea. But can I get a step drill that goes to 3/8" that won't be long enough to drill through the opposite side? Searching now....

      [edit] looks like I can... Thanks for the tip!
      Last edited by Royldean; 06-11-2015, 12:49 PM.

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      • #4
        option A

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        • #5
          Watch for the "un-even" chamfer / drill through with the limited step depth on a step drill.

          I'm in the "center pop, spot drill, then through drill" camp. I see no reason to use an endmill, unless that is all you have on hand. The spot drill doesn't even need to go all the way through the 065 wall, just give the 3/8th's drill a good start.

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          • #6
            This is what I use:

            http://www.homedepot.com/p/Kreg-3-8-...-KJD/100401246

            Center punch and drill.

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            • #7
              Best to use a 3/8 ball end mill. Just use it like a drill bit. Don't forget that endmills always drill a few thou. oversize. If you need it right on size, use a smaller ball endmill, then ream. Also, a solid carbide 2 straight flute drill works very nicely for that application.

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              • #8
                the plus side of using a step drill is also that you can deburr the outside edge of the hole if you're careful, plus they tend to leave less of a burr on the inside (drill exit) edge than do twist drills in thin material. Given that step drills are so short and rigid you shouldn't get any wandering.

                edit: these are what I use. They haven't been used intensively but they have held up really well drilling in all kinds of material (other than stainless). Work well in both a drill press and a hand held drill
                HF step drills
                Last edited by mattthemuppet; 06-11-2015, 02:49 PM.

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                • #9
                  The step drill can't really be used for a chamfer in this application, as the hole is in a curved surface. There is no real tolerance on the holes (±.050 would be more than enough).

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                  • #10
                    I did have a success once with thin tube, I centre drilled then opened the hole to the pin diameter of a counterbore, oddly that was 3/8, it went through the tube quite well, didn't catch, not much burr,but I was just messing about to see what I could do with a counterbore on tube, inquisitive day!
                    Mark

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                    • #11
                      Good point Roy, didn't think of that!

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                      • #12
                        Originally posted by mattthemuppet View Post
                        Good point Roy, didn't think of that!
                        It was mentioned in an earlier post ;-)

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                        • #13
                          Originally posted by Royldean View Post
                          I've already got it secured in Vee blocks nice and rigid. I've got to put roughly 36 holes in around the circumference and length, largest holes being 3/8".

                          Should I:

                          a) plunge with a center cutting endmill
                          b) spot drill, drill a small pilot hole, then plunge with the endmill
                          c) spot drill, drill with a small pilot hole, finish with a 3/8" drill
                          d) spot drill, drill through with a 3/8" drill
                          e) just be a man and use the 3/8" drill (i'm afraid of walking)

                          "a" makes the most sense to me, but I'm wondering if the endmill will grab when breaking through and do naughty things.....

                          Willing to consider an "f" if there is a better way. All I've got is a rockwell mill and a clausing lathe....
                          Here is a "tip" if you are drilling a series of holes "in line" down a tube.

                          Clamp a weighted arm to the work in such a way that the arm hangs down nearly to the floor, and the desired line of holes is "up".
                          With the work located by fixed Vee blocks, you can then move the work "down the line", knowing that the alignment of the holes will be maintained. (given an acceptable rough precision)

                          Just something I've done using an old lathe drive dog. 2 inch dogs might not be that common, but use your imagination.

                          That step drill from Home depot would be the cat's pajamas!

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                          • #14
                            Originally posted by CalM View Post
                            It was mentioned in an earlier post ;-)
                            okay okay, so I wasn't thinking or reading

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                            • #15
                              Unibit or step drill similar to this:

                              http://www.ebay.com/itm/Lenox-30886-...item19f661cfef

                              Nice round holes; quick, neat, and tidy. Get a set if you work with sheet metal and light plate.
                              Last edited by Forrest Addy; 06-12-2015, 05:21 PM.

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