New circle jig and driver cutout approach

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  • Ray_D
    Senior Member
    • Apr 2005
    • 164

    New circle jig and driver cutout approach

    I have been using a Jasper jig for several years and have found it less than terrific. I looked at the Router Buddy; but, it had some of the same issues and was expensive. So, I decided to make my own. First, I tried an approach that Pete Mazz posted several years ago that used a bushing guide and some holes drilled at the appropriate distances. It had the advantage that the router does not rotate so you do not get the cord windup; but, if you go half way one direction and then half way the other that issue goes away. I ended up moving on because I could not drill hole with the accuracy I wanted and decided an adjustable jig would be better.

    Below are some pictures of the jig I came up with. It is made up of mostly scrap. One piece of 1/2" MDF serves as the platform and has holes for the bushing guide and the T-bolt. The top piece has two pieces of 1/2" MDF glued to the bottom to provide a channel for a piece of T-track which carries the pivot pin. The pivot pin is 0.2" in diameter so that when I set it, I add 0.1" to the dimension I want and set that to the outside of the pin and router bit.


    The other thing I'm doing is using this to create patterns for the driver cutouts which are smaller than the driver frame OD by a fixed amount that can be rabbeted once the cutout hole is established. This minimizes the use of the jig and allows the pattern to be set before attacking the final baffle and I hope not prone to errors. Once you have the pattern you place it over the baffle where you have previously drawn the appropriate circle to confirm everything’s proper. Then you set the pattern aside and cut away most of the material inside of the circle. You the place the pattern and use a pattern flush trim bit to finish the cutout. Once the cutout is done, the recess for the driver is cut with a rabbet bit. Where I may do this a little differently is that I use slot cutter bits to do the rabbet. They are less expensive and also can make several depths by changing the bearing. They produce beautifully clean mounting surfaces for the drivers.

    Using a pattern gets away from needing the center pivot so that you can do repairs if needed after the hole is cut. You can do the rabbet after veneering.

    I hope this is helpful.

    Regards,

    Ray
    Attached Files
  • evilskillit
    Senior Member
    • Oct 2008
    • 468

    #2
    It looks like that works really well for you but I have to be honest. I don't 100% understand what you've done. Also I would imagine that not all drivers have the same flange width so you would need a bunch of different rabbet bits or at least a hand full of different bearings for the rabbet bits. I would imagine that would get a bit expensive as far as bits goes and would think that it might be a bit tricky to get a perfect recess. But then again I'm probably just misunderstanding something.

    I got a router buddy a few weeks ago, haven't had a chance to use it yet but it seems like it should be pretty neat. Simpler is still better tho.

    Comment

    • Ray_D
      Senior Member
      • Apr 2005
      • 164

      #3
      Things I forgot to say.

      It works a lot like the Router Buddy except that the base is not attached, although it could be. The plunge base with pattern bushing fits in a hole in the jig. When you use the jig, the router stays in the same orientation and the jig is rotated. It only takes a few seconds to make the cut. The hard part is setting the distance; same as the Router Buddy. Because the Router Buddy track runs offset to the bit, the minimum hole size is limited by that offset. The router also rotates with the Router Buddy. The jig as shown can cut out holes from just over 1” diameter to about 16 inches. I don’t think there is any reason it couldn’t be made to cut very large hole

      When making the pattern, only cut about ¼” deep and saw out the center staying away from the outer edge. Clean up the sawed edge with a pattern flush trim bit.

      There is no magic in mounting surface size. The cutout has to clear the driver frame and the mounting surface needs to be a reasonable size. With one slot cutter (MLCS #7664 $15) and one bearing (MLCS #249 $6) you can cut 9/16” and 7/16” surfaces which will suffice for a lot of drivers. With slot cutter #7665 ($16) you can cut 23/32” and 19/32” surfaces.

      You can see two of the patterns with slight recesses. They have no function on the pattern except to allow a check for size with the driver. Tweeters with those annoying side electrical connections can be placed face down to test the fit.

      When cutting recesses in the baffle, cut on the shallow side. You can always make it deeper, even after finishing (except for tweeters where the cutout has to be notched

      Ray

      Comment

      • Ray_D
        Senior Member
        • Apr 2005
        • 164

        #4
        Again

        There are a lot of extra holes in the top of the jig due to its evolution. I hope that is not confusing anyone.

        Ray

        Comment

        • abpc1
          Junior Member
          • Dec 2008
          • 6

          #5
          Here is a link to a commercially available product that works on the same principle. I have this and it works well; adjustability is top rate.

          Free support for loudspeaker projects, sourcing OEM speaker building supplies, and passive crossover design. We sell raw speaker drivers (tweeters, woofers, subwoofer, midrange drivers, full range drivers), speaker kits, amplifiers, capacitors, resistors, and inductors.




          Regards,

          Comment

          • Ray_D
            Senior Member
            • Apr 2005
            • 164

            #6
            Looks Good

            Originally posted by abpc1
            Here is a link to a commercially available product that works on the same principle. I have this and it works well; adjustability is top rate.

            Free support for loudspeaker projects, sourcing OEM speaker building supplies, and passive crossover design. We sell raw speaker drivers (tweeters, woofers, subwoofer, midrange drivers, full range drivers), speaker kits, amplifiers, capacitors, resistors, and inductors.




            Regards,
            Thanks for the links. I was not aware of this product. It seems to address most of the problems I had with the Jasper jig, the biggest was having to lift it up every time you wanted to change the radius and having the pivot pin stay stuck in the baffle. I could have drilled a bigger hole but that just leads to sloppy work. Being able to adjust the radius from the top side is a big time saver. That is an issue with the Router Buddy I think.

            Ray

            Comment

            • NoDestiny
              Member
              • Jan 2009
              • 97

              #7
              What about this one? Anybody have experience with it?

              ToolBarn.com offers a large selection of online power tools, hand tools, nail guns, fasteners & pressure washer parts from top brands like Milwaukee, DEWALT, Karcher, Senco, Makita & more!

              Comment

              • cjd
                Ultra Senior Member
                • Dec 2004
                • 5568

                #8
                Originally posted by NoDestiny
                What about this one? Anybody have experience with it?

                http://www.toolbarn.com/bosch-ra1054.html
                I use that for really big holes (subwoofer, etc), but it doesn't work well at all for small work. I had to do a custom thicker base on the router as well. The one at Madisound looks really nice - might have to snag one of those! Probably would pair quite well. The downside is that it's not set-and-forget once you have the right hole size for a given driver.
                diVine Sound - my DIY speaker designs at diVine Audio

                Comment

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