Finger joints are used in woodworking to hold pieces of wood together. The fingers interlock to form strong and stable corners and joints. Finger joints are commonly used to make both decorative and functional boxes in woodworking.
Cut a 30-inch long board out of the 2-foot-by-6-foot board. The rest of the 2-foot-by-6- foot board is going to be used as the miter saw gauge extension. Measure 13-inches on the 2-foot-by-6-foot board and mark it with a pencil.
Place the dado blade on the miter saw. Set its width to match the thickness of the board with which you are going to be making a finger joint. For example, a board that is 3/4-inch thick requires the miter gauge to be placed at 3/4-inch width setting. Place the height of the dado blade 1/32-inch higher than the board's thickness. Continuing with our example, the 3/4-inch thick board needs the dado blade's height to be set at 13/32-inch high.
Place the miter gauge extension board onto the miter saw table and line the pencil mark up with the center of the dado blade. Cut the board on this line. Measure 3/4-inch over from the cut and make a line with the pencil. Cut the board on this line to make the first finger of the joint.
Measure and cut out a board that is 6-inches long by 3/4-inch high and 3/4-inch thick to make the key for the finger joint jig. Place the key in the first cut you made on the board and secure it into place with a screw that is set below the wood's surface, or countersunk into the wood.
Line up the second cut with the dado blade, and secure the miter gauge extension to the saw's miter gauge with a clamp.
Take the wood that you are going to be making the finger joint out of and stand it on end so that it is resting flat against the extension and has one edge up against the key of the finger joint jig. Clamp it in place against the extension. Push the wood forward through the dado saw blade, using the extension guide to cut the wood to the correct size.
Pull the board back towards you over the blade. Place the cut-out section or tenon over the key and use it as a guide to make the second cut. Continue cutting fingers into the board. Move on to the other boards once the first one is done. Fit the finger joints together. Place a clamp onto them and glue them into place.
To hold the extension of the finger jig to the miter gauge, you can also be done by driving two screws through the holes in the miter gauge into the back of the extension.
Always wear safety goggles and ear protection when using saws. Take care when running a saw so that you do not cut yourself or harm others.