Here is another solution: Most of the swing bottom and back supports I have seen are a simple half lap joint. Is this what you want to make? If so a cut off sled is the answer. First off get a piece of 1/4" hardboard that is 2" wider than the distance from your bit to the edge of your table a perhaps 30" long. Glue and screw a piece of 1 x 2" along the edge and using the side of your table as a guide make a pass from right to left. This will give you a nice clean cut line. Next, mark the angle you want to cut on your wood. Align your marks with the cut edge of the sled. To hold your wood in place attach double sided carpet tape to the bottom of a piece of 2 x 4" and place it on the right side of your wood. Make sure it extends over the cut edge of your sled by an inch. This will serve as your push block and help prevent tear out. Make a pass, move your wood down a bit and repeat until you complete the cut. If you are going to make many of these swings screw the 2 x 4" backer to the sled. You will need different angles for each side of the joint so either build another jig or position a second backer at the other end of your sled.
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