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  • Antenna Base

    My friend and customer Ray designed a base for a Ham radio antenna that will eventually be mounted on top of a school, which is the highest point in the area. I machined all of the components for the antenna base. The antenna will be used for a Ham radio repeater station. The school didn’t want him to drill holes through the membrane of the roof, so it has to rely on weight and a large base to keep it from tipping over in the wind. The first step was to face and cut the stock to length.

    1. Cutting Off Stock 1
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    2. Cutting Off Stock 2
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    The next step was to set it up on the Bridgeport to cut the slot. I removed the chuck from the lathe and clamped it to the Bridgeport. Then I used a center finder to find the center of the stock so that I could zero my digital read out.

    3. Finding Center
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    Next, I drilled the center hole undersize just to remove some stock. In hind sight I should have done this step while the base was still in the lathe. (It is easier to drill a hole with the 7-1/2 HP lathe as opposed to the 1 HP Bridgeport.

    4. Pilot Drilling Stock
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    5. Drilling Stock
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    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Colchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

  • #2

    The next step was to cut the slots. I used a 1” roughing end mill. The depth of cut per pass was .050” and the speed was 800 rpm. The roughing cutter is a six flute endmill. The finishing cutter is a four flute endmill.

    6. Roughing Cutter
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    7. Finishing Cutter
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    The last mill operation was to tap the four 5/16-18 UNC holes. I tap drilled the four holes deep enough to provide room for chips, so that I could use a spiral tipped endmill. I tapped ½ inch under the power of the Bridgeport then backed off to clear chips. I tapped the last ¼ inch by hand. I have some spiral fluted end mills, which would push three chip streams out of the hole, but the ones that I have aren’t designed for steel.

    8. Tapping four holes
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    The next step was to go back on the lathe to bore and counter bore the center hole. If I were smarter, I would have done this during the first lathe cutoff and facing operations.

    9. Boring Base
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    10. Counter Boring Hole
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    Last edited by Don52; 05-03-2021, 05:24 PM.
    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Colchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

    Comment


    • #3
      11. Chamfering Bores
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      And here is the base all done with lathe and mill operations:

      12. Base All Done
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      The next step was to drill and countersink the legs followed by chamfering the end of the leg. My 45° chamfering end mill has enough flutes that I can cut a 3/8” chamfer in steel in one pass – very nice.

      13. Chamfering Leg 1
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      14. Chamfering Leg 2
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      I really like the M. A. Ford style of countersink because it cuts clean without chattering. They can also be used on a drill press, because they are self-centering.

      15. Countersinking legs
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      Miller Thunderbolt
      Smith Oxyacetylene Torch
      Miller Dynasty 200DX
      Lincoln SP-250 MIG Welder
      Lincoln LE 31 MP
      Lincoln 210 MP
      Clausing/Colchester 15" Lathe
      16" DuAll Saw
      15" Drill Press
      7" x 9" Swivel Head Horizontal Band Saw
      20 Ton Arbor Press
      Bridgeport

      Comment


      • #4
        16. Legs Done
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        I drilled the scrap piece left over from the base. I figured the antenna mast could use some additional mass to keep it from tipping over in the wind.

        17. Drilling the scrap as a counterweight
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        The next step was the mast. I added a cap to the top to keep it from filling with water and possibly freezing or corroding. The other side had a collar to trap the mast in the base and to prevent it from rotating relative to the base. (The scrap tubing was just to show you how the pieces fit together.)

        18. Making caps for the mast
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        19. Three mast pieces in exploded view
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        20. Three mast pieces together
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        Miller Thunderbolt
        Smith Oxyacetylene Torch
        Miller Dynasty 200DX
        Lincoln SP-250 MIG Welder
        Lincoln LE 31 MP
        Lincoln 210 MP
        Clausing/Colchester 15" Lathe
        16" DuAll Saw
        15" Drill Press
        7" x 9" Swivel Head Horizontal Band Saw
        20 Ton Arbor Press
        Bridgeport

        Comment


        • #5
          I welded the cap to the top and the collar piece to the other side.

          21. Cap welded to mast
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          22. Other end welded to mast and dressed
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          Next, I assembled the antenna mast components.

          23. Mass inserted into base
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          The collar on the other end of the shaft was .005” proud of the counter bore, so when the legs were bolted on, they would clamp the mast shaft to prevent it from rotating.

          24. Mast proud of base
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          25 Legs clamped to base
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          Miller Thunderbolt
          Smith Oxyacetylene Torch
          Miller Dynasty 200DX
          Lincoln SP-250 MIG Welder
          Lincoln LE 31 MP
          Lincoln 210 MP
          Clausing/Colchester 15" Lathe
          16" DuAll Saw
          15" Drill Press
          7" x 9" Swivel Head Horizontal Band Saw
          20 Ton Arbor Press
          Bridgeport

          Comment


          • #6
            And here is the antenna mast base all done. The counter weight, which is not shown, would slide on the mass and rest on the base to add additional weight to the base.

            26. Antenna Base All Done
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            -Don
            Miller Thunderbolt
            Smith Oxyacetylene Torch
            Miller Dynasty 200DX
            Lincoln SP-250 MIG Welder
            Lincoln LE 31 MP
            Lincoln 210 MP
            Clausing/Colchester 15" Lathe
            16" DuAll Saw
            15" Drill Press
            7" x 9" Swivel Head Horizontal Band Saw
            20 Ton Arbor Press
            Bridgeport

            Comment


            • #7
              Very nice job........and nice shop....on that lathe chuck removal, what type of mount is that? Is that a D1-6 ? with pins to remove? ..........I have a Dividing head and rotary table......both see limited use , but nice to have when the need arises... Click image for larger version

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              • #8
                Originally posted by tarry99 View Post
                Very nice job........and nice shop....on that lathe chuck removal, what type of mount is that? Is that a D1-6 ? with pins to remove? ..........I have a Dividing head and rotary table......both see limited use , but nice to have when the need arises.
                My chuck is a run-true chuck, which has an adapter that has the D1-6 pins on one side and a boss on the other. The chuck has four set screws that push on the boss. The set screws are used to center the chuck relative to the adapter. Attached are some pictures.

                1. Chuck adapter mounted
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                2. Adapter removed
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                3. Back view of chuck
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                ​​​​​​​-Don
                Miller Thunderbolt
                Smith Oxyacetylene Torch
                Miller Dynasty 200DX
                Lincoln SP-250 MIG Welder
                Lincoln LE 31 MP
                Lincoln 210 MP
                Clausing/Colchester 15" Lathe
                16" DuAll Saw
                15" Drill Press
                7" x 9" Swivel Head Horizontal Band Saw
                20 Ton Arbor Press
                Bridgeport

                Comment


                • #9
                  Good, clean work Don.

                  Comment


                  • #10
                    Originally posted by ryanjones2150 View Post
                    Good, clean work Don.
                    Thanks, Ray picked up the antenna this afternoon.
                    Today I also finished machining a manifold for Ray’s consulting job, which is for a automotive paint equipment supplier.

                    -Don
                    Miller Thunderbolt
                    Smith Oxyacetylene Torch
                    Miller Dynasty 200DX
                    Lincoln SP-250 MIG Welder
                    Lincoln LE 31 MP
                    Lincoln 210 MP
                    Clausing/Colchester 15" Lathe
                    16" DuAll Saw
                    15" Drill Press
                    7" x 9" Swivel Head Horizontal Band Saw
                    20 Ton Arbor Press
                    Bridgeport

                    Comment

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