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Utilizing the dovetail ram on my Bridgeport

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  • Utilizing the dovetail ram on my Bridgeport

    I've been scouring the "universe" for discussion on the the use of the movable ram on my Bridgeport, and not having any luck.

    I need to drill a 170 holes in a 23in x 23in x 1/8in aluminum panel, as well as mill a couple DB9 connector openings. I could do it by hand drilling but I'd like to make use of the relative accuracy of my machine along with the DRO.

    I have 12in of "Y" travel on the knee, so I should be able to do it with 2 setups, rotating the work 180 degrees between setups (kinda clumsy I know).

    But I have nearly full travel on my Vram, so I'm wondering if I can utilize the combination of the knee "Y" travel and Vram travel and DRO to provide the means to do the entire job in a single setup.

    I can visualize how I might do it, but I'm sure there must be some wily and crafty info somewhere on the web.

    Can anyone point me to some techniques and tips and tricks type of info for doing such an operation?

  • #2
    To avoid installing a DRO scale on the ram itself, you could install a reference point on the table and a dial indicator to "zero" the ram in the new position for the second half of the job.
    Helder Ferreira
    SetŮ’bal, Portugal

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    • #3
      It's not hard. Simply drill half the holes. Move the head out and use test indicator to pick up a hole, zero dro and keep going. The one thing you need to check is that the v-ram is 90.0 degrees to the mill table.

      I've used this many times at work when machining large plates.

      Sent from my LGLS775 using Tapatalk

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      • #4
        I would spin the material.

        1) mount the material on a same sized piece of 3/4 plywood.

        2) Drill as many holes as possible

        3) rotate/spin the part 180 degrees

        4) use drill placed in one of the previously drilled holes to create a new X and Y on the DRO

        5) with drill still in the hole check the set-up for square to the table.

        6) Drill the second set of holes. Depending upon the arrangement of the holes you might still have to move the set-up a second time to hit all the holes. If so use the DRO to reset values same as step 4)

        7) You might want to use some of the first holes to screw the panel to the plywood to insure that is does not move. Do this before making the first un-clamp and move.

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        • #5
          If you have a DRO, the scale on the back of the table will limit travel to the rear. On mine, I lost about an inch. To be safe, I made use of the hard stop bracket on the X travel that was on my machine. I get about 11" of X according to my DRO but less than that is actually usable. I have my ram extended about 3" for the horizontal attachment I plan to get.

          Keep in mind that the ram travel does not extend the X travel--It effectively reduces it. I would use the flip and re-set method as you would have considerable work overhang otherwise. And the DRO scale could have you moving it twice if the hole pattern is more than ~22"

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