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  • How do I fix this?

    I just now looked at the baffles for a project and the woofer holes are 0.014 too small! Either the CNC guy dialed in the wrong diameter or I told him the wrong diameter. Either way, I have to sand off 14 thousandths.

    Is there a way to do this other than to manually sand it?

  • #2
    Re: How do I fix this?

    Originally posted by johngalt47 View Post
    I have to sand off 14 thousandths.
    If this is MDF, that ought to take, oh, about ... 28 seconds? :rolleyes: :p

    Comment


    • #3
      Re: How do I fix this?

      Several ways, most of them bad and guaranteed to give you an out-of-round hole. Wrap some 100 grit paper around a dowel and sand by hand.

      Alternatively if you're careful use a sanding drum in a Dremel or drill.

      BTW did you try to fit the drivers or just measure the hole against what you thought?
      Last edited by fastbike1; 02-05-2012, 09:53 AM.
      I was so much older then, I'm younger than that now.
      OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
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      LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

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      • #4
        Re: How do I fix this?

        No, the way I discovered it was trying to set the driver in the hole. Just barely wouldn't fit so I measured it.

        I'm just trying to keep from having an out of round hole or damaging the baffle around the hole. It is the baffle that comes with the Madisound 38L cab.

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        • #5
          Re: How do I fix this?

          Here's what you do. Use a router with a bearing guide at the bottom and a slightly increasing cut up toward the router. I don't know what that bit is called, but I have one. I think it's for triming laminate. Go around the cutout taking off a little bit of the top part of the hole. Then take a bit with a bearing at the top that makes a straight cut. The bearing rides where the cut was just made, so the new hole will be slightly larger.

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          • #6
            Re: How do I fix this?

            Are you going to, or is the hole already, back cut? This is almost mandatory for drivers 6.5" and smaller. I bet once that's done, you won't notice or you'll have very little sanding to do.
            - John

            "Injustice anywhere is a threat to justice everywhere." - Dr. M. L. King
            www.BuildTheDream.org

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            • #7
              Re: How do I fix this?

              A handheld rasp is perfect for this task.

              Like the guys above said, it's pretty quick to do... and there's little chance of damaging anything. I usually start by chamfering the hole at a 45 degree angle and proceed further if necessary.

              Click image for larger version

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              ~Marty

              Baby Eidolons
              Sapphos
              Cables (Post #54)
              Other speakers (Post #21)
              Design Thoughts (Posts: 6,10,13,33,35)
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              • #8
                Re: How do I fix this?

                Originally posted by johngalt47 View Post
                I just now looked at the baffles for a project and the woofer holes are 0.014 too small! Either the CNC guy dialed in the wrong diameter or I told him the wrong diameter. ...
                It's possible that you were both working with the right numbers. Also possible, the cutter was small or cut small (pushed material out instead of shaving it), or the bit shaft flexed.

                When I tried CNC I got a smaller than theoretical holes (similar amount to yours), fortunately I still could press in the drivers. So I left it.

                In the future I will be learning how to bump up the diameter while it is still mounted in the CNC router.

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                • #9
                  Re: How do I fix this?

                  Originally posted by ReissM View Post
                  A handheld rasp is perfect for this task.
                  8" 4-Way Shoe Rasp

                  Should be one in every tool box.
                  "It suggests that there is something that is happening in the real system that is not quite captured in the models."

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                  • #10
                    Re: How do I fix this?

                    I wasn't very clear on this. It is the rebate cut, not the through hole. The through hole is just fine, the rebated portion is what is too small.

                    Since the baffle is prefinished with black paint, I don't want to make any mistakes with this.

                    Oh, and the rebate is only like about 1/4" deep, the thickness of the driver's flange.

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                    • #11
                      Re: How do I fix this?

                      You may be able to adjust a rabbet bit to cut a little more than is there. A bit of tape wrapped around the bearing can help when you need something in between you noraml bearing sizes.

                      Really, for the small amount you want, sandpaper around a dowel is the simplest way. Just go easy and try the driver every few passes.
                      I was so much older then, I'm younger than that now.
                      OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                      Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                      Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                      Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                      LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                      Comment


                      • #12
                        Re: How do I fix this?

                        I had the exact problem when trying a slightly larger tweeter. I just used a short template router bit(the kind with the bearing on the top. Then I just used the driver recess as a guide and cut the driver recess a total of 5/8" deep and then cut a disc with the Jasper circle jig and router out of 5/8" mdf and glued it in place. Since the disc has a center hole already form cutting it out, I then used my router with a Jasper circle cutting jig to cut a slightly larger recess for the new tweeter.

                        Chris
                        Chris

                        Goofing around since 2000.

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                        • #13
                          Re: How do I fix this?

                          Originally posted by fastbike1 View Post
                          Really, for the small amount you want, sandpaper around a dowel is the simplest way. Just go easy and try the driver every few passes.
                          Good advice Fastbike. I've had to do this once or twice. It won't take very long and there's very little risk of messing up... like there is with a router. (it only takes 0.3 seconds to ruin a nice cabinet with a router accident.)

                          Listen to FastBike, you'll be glad that you did.
                          ~Marty

                          Baby Eidolons
                          Sapphos
                          Cables (Post #54)
                          Other speakers (Post #21)
                          Design Thoughts (Posts: 6,10,13,33,35)
                          Boundary Augmentation
                          Dispersion/Interference

                          Comment


                          • #14
                            Re: How do I fix this?

                            Yeah, I'm using the sandpaper around the dowel but it is taking some time. I have 4 holes to do...

                            Comment


                            • #15
                              Re: How do I fix this?

                              Originally posted by johngalt47 View Post
                              Yeah, I'm using the sandpaper around the dowel but it is taking some time. I have 4 holes to do...

                              What if... You cut a circle out of 3/4 mdf that is about 1/4" smaller outside diameter. Use self sticking sandpaper on the edge of the disc. Make some big knobs that are comfortable to your hands so that you can work it without your fingers cramping up. Also, since the radius is close, the sandpaper contact should be better.

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