Dominic's Finger Joint Jig

A router master plants the seads for a solution.

SHOP OWNER: Dominic Greco
LOCATION: Richboro, PA

    About a week ago, I posed the question - "Why can't I use my dado chippers to cut finger joints?". I built the Finger Joint Jig from WOOD magazine and was unsatisfied with the quality of the cuts I was getting with my Delta Dado set. I received replies from various regulars here, but one from Bill Hylton struck a cord. He suggested I scrap the idea of using the tablesaw altogether and use a router table.
    I actually had thought briefly about fabricating a false top for the router table, complete with miter slots so I could use the jig as is. I mentioned this to Bill and he said that I could get by just using a set of trap fences as shown in his book, "Woodworking with the Router". Bill went on to say that I could use some scrap luan or plywood and that they needn't be the type of thing you'd need to save. I took Bill's suggestion and stewed on it a while. Finally, I came up with the solution that would work best for me.
Dominic's Finger Joint Jig

    Since I had a lot of -inch hardboard scraps laying around the shop, I decided to use that material to make the trap fences. I know Bill suggested that I just use some scrap, but I couldn't resist making these trap fences nice enough to save. I cut the two pieces for the left and right hand trap fences 1" longer than my top is wide (26 1/4") x 12" wide. At the front and back of each trap fence, I glued and nailed a 1" wide x 12" long x 1/2" thick piece of mahogany. This would help me place the fences, and act as a stop when I clamped them down. I haven't applied any sealer to these fences yet. However, I plan to once I get a chance. They'll be no good if they warp.
Dominic's Finger Joint Jig

    If you look at the photo, you can see that the right hand trap fence has a cutout that fits over the bit opening. One of the restrictions that I had with my finger joint was that I had to leave a section of the base unobstructed so that I could install alternate adjustable key assemblies for cutting different size finger joints. This meant that I had to install the slide base off to one side of the jig's bit opening.
Dominic's Finger Joint Jig

    The slide base on the finger joint jig is approximately 9" long x 7" wide. This was secured to the base of the finger joint jig with several screws. If you look at the picture above, you can see how I had to install the slide base as to avoid the adjustable key assembly.
    One thing I should mention here. Since a router bit is being used to cut the finger joint slots, rather than a table saw blade, there is no requirement that the slide base be installed perfectly 90 to the face of the jig. This made life a bit easier. With the base installed, I gave it a coat of sealer. After that dried, I applied a coat of paste wax.
Dominic's Finger Joint Jig

    With the jig completed, I was ready to cut some test pieces. I placed the trap fences on the router table with the jig sitting between them. I then clamped the fences down, while maintaining pressure against the finger joint jig's slide base. With everything clamped, the base slid back and forth between the trap fences quite easily. I clamped a 4" diameter flex hose from my dust collector into position and I was ready to start. Now all I needed was some practice stock.
    Since I didn't want to practice on any of my good stock, I decided to look in the scrap pile. I had some old oak drawer sides that my father-in-law had given me some time back. I surfaced these to a consistent 5/16" thickness and began. The jig worked just as well as I had expected. I just followed the directions from the magazine article and was able to make well fitting finger joints with minimal fiddling.
    I did learn that no matter how hard you try, you cannot compensate for your router bit being loose in the collet (it took me a couple minutes and two practice cuts to figure that one out)! I also learned that the combination of a zero clearance insert, ganging similarly sized pieces together, and scoring them with a marking gauge goes a long way to reduce the tear out.
Dominic's Finger Joint Jig

    As you can see, the practice pieces turned out so nice I decided to make boxes out of them! I have some resawn walnut that will work nicely with the red oak.
    Thanks to Bill's timely suggestion, I was able to finally make finger joints without spending additional money for a new dado blade.

. . . Dominic Greco



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