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Aligning The Wings On A Neck-Through With Dowel Pins

Discussion in 'Luthier's Corner' started by Bruce Johnson, Nov 28, 2017.


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  1. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    On several recent project threads, such as Mapleglo's 3rd Devil Bass project, we talked about techniques of aligning the body wings to the center spine of a neck-through style bass.

    I don't make many neck-through instruments these days, but I happened to be helping Mike Lipe with one this week. It's a custom Flying V guitar, with a flame maple neck, mahogany wings, and 1/8" flame maple top and back on the body. A flaming V! It also gets a Rocklite fingerboard, an ebony headstock cap, and some fancy inlay work by our buddy Ron Thorn. Pat Wilkins will be painting it.

    I machined up the neck blank from a long flame maple board, and installed my usual truss rod. We decided on a built-in 2 degree neck angle. The tang (the part that extends through the body) is 3 1/2" wide x 1 1/2" thick. With the top and back caps, the body will end up a little over 1 3/4" thick. I had to work the layout carefully to get the vertical offsets right. I used one of my trusty router fixtures to flatten the top and back surfaces of the tang. I planed the mahogany board that we got for the wings to just a bit over 1 1/2", and sawed it in two.

    Here are the partially-machined neck and the mahogany blocks on my bench.

    IMG_5323B.


    The tricky part of a neck-through project like this is planning out the sequence of operations. First, I'm machining the main structure of the neck, including the tang. Then, I'm fitting the blocks to the tang, aligning them accurately with dowel pins, but not gluing them on. From there, I glue on the fingerboard, radius and slot it, and glue on the headstock cap. Then the neck goes off to Ron for the inlays.

    Meanwhile, I've left the wings as rectangular blocks. The shape is drawn on them, but not cut out. Mike will now rout out the control cavities and some chambering, and drill connecting holes for the wiring. Those operations are all easier working with the rectangular blocks. Then he'll saw them out to shape.

    When the neck gets back from Ron, Mike will shape the back of it and put in the frets. Then the mahogany wings get glued on, using the dowel pins. After gluing, the top and back surfaces get trued up on Mike's big pin router. The flame maple top and back plates get sawn out oversize, and the top gets carefully fitted around the neck heel. The top and back plates get glued on, then the pickup cavities get routed, and finally the perimeter of the body gets routed. That's the general sequence. Lots of potential for making mistakes. Engineering is required.

    Anyway, the point of this thread is to show you my method for aligning the wings and neck tang with dowels. I usually use small 1/8" dowel pins, two on each side. I made up this simple drill fixture many years ago, and I've used it on, I think, every neck-through project since.

    IMG_5329B.
    Not much to it. It's a strip of 1/2" MDF with three 1/8" drill bushings installed in a line that's 1" down from the top edge. On most bass bodies, I use the front and back bushings. On this V, the wings are shorter in length, so I used the first and second bushings.

    IMG_5324BX.
    On the top edge are a couple of sheet metal screws and big washers. The little L-shaped thing is a reference pin. It's a piece of 1/8" piano wire, rounded off on one end and bent to make a handle. I have several of these around the shop that I use for temporarily pinning fixtures and templates in place. The bent end makes it easier to push in and pull out.

    The key thing about this drill guide is that it's symmetrical. You can drill through it from either side. It references from the end and those top washers. That's how it makes the holes in the two mating pieces perfectly aligned.

    Here's the process:

    IMG_5325BX.
    First, I position it on the side of the tang, seating the washers against the top surface and aligning the end with the edge of the mating surface. I just hold it in place while I drill the 1/8" hole about 3/8" deep. In the picture, my other hand is holding the camera!

    IMG_5326B.
    Then, I plug the reference pin into the front hole, to hold the drill guide in place, and drill the rear hole. This ensures that the holes are accurately spaced to each other, and to the the top edge.

    IMG_5327BX.
    Then, I flip the drill guide over and repeat the drilling on the body wing. The washers are seated against the top surface, and the end is lined up with the pencil mark of the final cut shape.

    IMG_5328B.
    And that's it. The parts are now accurately aligned and pinned. They can now be temporarily assembled to do some operations, and then pulled apart again. For temporary assembly, I'll usually use standard steel 1/8" x 3/4" dowel pins. For the final glue up, I use white plastic Plastruct 1/8" rod stock, the same as I use for my side dots. The plastic pins make it easier if someone ever needs to unglue or saw apart the joint.
     
  2. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    Per usual, a brilliant little jig. I have one of the “vise” type self-centering dowel drilling jigs, I think I used 3/8” dowels. It worked well, but is designed for centering dowels in a given thickness, so you have to add shims to get holes offset of centerline. You also have to rely on aligning the jig with a pencil mark on each piece, which works, but the accumulated tiny error over multiple dowels makes it a tight fit. I did the same thing with body wings, leaving them rectangular until all the routing was done, same with the neck.
     
  3. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    If I may suggest Bruce should change his nickname to Bruce Jig. So many clever and ingenious jigs time after time.
     
    MattZilla and Gilmourisgod like this.
  4. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    At one of my past corporate jobs, my nickname was Professor Gizmo. It came from a classic Far Side cartoon, which showed Professor Gizmo and his many inventions.
     
    ctmullins, RBS_Johnson and rwkeating like this.
  5. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    You have all kind of gizmos and gadgets on your shop. Do you have any jigs that you have no clue what was it made for?
     
  6. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yes, that actually happens. I'll be pawing through a cabinet or shelving unit, and pull out some fixture or special tool, and I can't remember when or what I built it for. That's what happens as the years pile up.
     

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