FINGER JOINT JIG MODIFICATIONS
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.
Since I had a lot of ¼-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.
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.
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 90º 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.
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.
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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