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Drilling a ROUND Hole

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  • Drilling a ROUND Hole

    I remember reading here about drilling in thin material with a standard drill bit, the hole is 3 sided so to speak. And it happens. So how to drill a round hole? I simply have some plastic gas can vents, to make those blasted new cans more usable. The maker says to drill a 31/64 hole and push in this vent. I have both plastic and metal cans I want to drill, and I would bet they won't drill round. I have the drill bit but not a chucking reamer that size. Ideas?

  • #2
    For perfectly round holes in thin metal get hold of an old adjustable reamer and reverse all of the blades so that they'll cut a taper. Drill a pilot the size of the small end then open up the hole with the reamer in a battery drill to your required diameter. Perfect round and burr-free holes.
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

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    • #3
      Uni-bit/step drills will make a nice round hole in sheet metal but there is limited sizes.

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      • #4
        -uni-bit
        -reamer
        -workpiece clamped between two sacrificial blocks (hard plastic, wood, aluminium
        -sheet metal drill (almost like brad point drill)
        -punch instead of drill
        Location: Helsinki, Finland, Europe

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        • #5
          Holesaw.
          Or use the rag trick.

          Last edited by redlee; 11-11-2020, 04:42 PM.
          Beaver County Alberta Canada

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          • #6
            Find a CHEAP step drill (unibit) and turn the next larger step to size,
            It's all mind over matter.
            If you don't mind, it don't matter.

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            • #7
              I didn't have any problems drilling the holes for the vents in the plastic cans. And the holes came out round. For the metal cans, put a block of wood over where you want the hole and drill thru the block and the metal at the same time. The resulting hole should be good enough for the vents.

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              • #8
                Originally posted by rws View Post
                I remember reading here about drilling in thin material with a standard drill bit, the hole is 3 sided so to speak. And it happens. So how to drill a round hole? I simply have some plastic gas can vents, to make those blasted new cans more usable. The maker says to drill a 31/64 hole and push in this vent. I have both plastic and metal cans I want to drill, and I would bet they won't drill round. I have the drill bit but not a chucking reamer that size. Ideas?
                Do a search for replacement nozzles, the old style. A vent hole also helps.

                Hal

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                • #9
                  use a drill for wood.

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                  • #10
                    Originally posted by rws View Post
                    I simply have some plastic gas can vents, to make those blasted new cans more usable. The maker says to drill a 31/64 hole and push in this vent.
                    Are you New? In Plastic you said. Thats a Soldering Iron job. JR

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                    • #11
                      Thin stuff id imagine that a unibit or a spur/brad point drill would do best, long as you needed round more than precise size. If you wanted precise size too, either reaming or boring

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                      • #12
                        Originally posted by JRouche View Post

                        Are you New? In Plastic you said. Thats a Soldering Iron job. JR
                        No, I'm not new

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                        • #13
                          I've never tried the "rag trick" but what I have done when it comes to drilling through thin material is use a guide block like the one in my picture.

                          With this I was able to cut a clean hole through .0005 shim stock.

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

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                          • #14
                            The guide block is the best way for thin flat material. I have a couple of boxes of sheet metal drills, for drilling for 1/8" rivets, they are stub form and the sides do not have any relief like ordinary twist drills. The cylindrical outside reduces the lobing that ordinary drills can produce.

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                            • #15
                              Originally posted by old mart View Post
                              The guide block is the best way for thin flat material. I have a couple of boxes of sheet metal drills, for drilling for 1/8" rivets, they are stub form and the sides do not have any relief like ordinary twist drills. The cylindrical outside reduces the lobing that ordinary drills can produce.
                              I never had any trouble drilling 1/8" holes in sheet metal for rivets. The problem starts with larger size drills. On sheet metal I have found it starts at about 1/4".

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

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