Articulating Router Arm and Universal Workboard

Articulating router arm rev. 3 with T-slot universal workboard

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This articulating arm router idea is certainly not original to me, but mine has been through a few revisions now and I thought I would bring the project up to date. This whole thing started with discussions at Charles Fox's guitar building class in summer '94. Originally it was thought that one of those dental tool holders, the one they put all the implements of pain on right in front of you so you can look on them in anticipation while they ask questions and have their hands in your mouth, you know the ones. I went to the local surplus medical equipment place and found one I thought might work. Actually I bought 2 of them, one for me and one I promised Charles if I found a bargain. I couldn't get the thing to work and neither could Charles so it was back to the drawing board. A few months later I was looking through an industrial supply rag, isn't it interesting the things guitar makers do for fun? Anyway, there was this articulating arm that was pictured with a guy using it for tapping screw threads in a metal plate... looked perfect, I had found the holy grail articulating arm router fixture. I called the company to ask the price and they said something in excess of $4000, so much for my excitement. However, they said they had a color brochure with a good picture and description so they sent me one. The brochure was good enough to get me going and with this article you will be brought up to date.
Articulating Router Arm Contraption This contraption is mostly 3/4" sq. aluminum tubing and 1/4" aluminum plate. I'll let the pictures do most of the explaining and I don't have a good drawing of the thing so please bear with me on this.
Shoulder Bolts The most important recent revisions were the addition of the shoulder bolts and bronze bushings in all the joints, I originally had just bolts through wood in the joints with resulted in poor performance. The other and most recent revision is the main sleeve bearing assy. The whole arm swivels on this bearing and there is no play in it, very important. Bronze Bushings
Joints The joints all rotate on a thin layer of teflon tape I inserted between the surfaces of the aluminum square tubing and the 1/4" plate. You can see it as little white pieces sticking out of the joints in a couple of the pictures. I'm sure UHMW plastic would do the same job, and it is more available and cheaper for sure. Here are a few points of consideration

The arms should be at least long enough in their combined length to reach across the long dimension of your work plus about a foot.

The joints need to be as accurate as possible for the arm to allow good perpendicularity (if that is a word) throughout the travel of the arms. Drill both of the double plates and all four of the single plates clamped together if possible. A good sharp drill and drilling fluid helps also.

Length of Arms and Accuracy of the Joints
Universal Workboard Now the universal workboard. This is a way cool device I was introduced to along with some other "Lintians" at Fred Carlsons master class last February. It is basically 1" MDF with 5/16" dados on 3" centers. The T-slots are routed with a special T-slot bit from Rockler they sell for their T-slot hardware. I use the Rockler T-slot bolts and knobs; the aluminum tracks don't seem necessary. Fred used modified carriage bolts, and John Timblin says toilet tank to bowl bolts would work also.
The L brackets are from José Romanillos as credited by Fred and mine are MDF rabbetted. Make plenty of these as you will want to modify them in many ways to fit different shapes.
Also just recently I found at McMaster Carr some bolts that will work for T-slot hardware in the Delta Unisaw, and I suspect other saws. I have been trying to find something like this for a while as my table saw gets used as a work surface more that a table saw anyway. They are called elevator bolts and the ones I used are as pictured. They have many sizes; I chose the 7/8" dia. Head units to fit my T-slots. It might be a better idea to use a larger dia. head and grind flats on it so you could get a lock in the T-slot and a longer bolt. The 7/8" work great for me anyway and it was a great find.

Elevator Bolts