Not every jig needs to be complicated, and this jig is one of the simplest, yet most effective jigs you can make for cutting dados. It's ideal for anyone who wants to make a shelving unit and want to make sure the shelves are securly connected to the sides by having them inset into dado. The jig is quick and easy to set up, and it's variable, meaning you can use it for any depth of shelf you want and you don't even need to measure them, you can use the actual shelf that you have to set the width of the dado, then simple clamp the jig to your end boards and start cutting ... it's that easy.
Watch it on Youtube: https://youtu.be/GzWQdlmGtRQ
I made mine form 3/4 inch plywood because it's stable, thick and sturdy and won't easily (if at all) warp or crack, and will give me many, many years of service ...
Most shelving units are about 12 inches wide, so I decided to make my jig slighly wider at 14" in case I wand something wider, so i started off with a piece of 3/4 plywood that was 14 wide by just over 20 inches long. I also needed a very straight piece of wood for the stopper at the front of the jig and chose a nice straight piece of Alder that was 1-1/2 inches wide and 3/4 inch thick and the same length as the plywood. I then ran this piece os wood through my joint to make sure it was absolutely straight.
I then pre-drilled 4 holes in the stopper piece and attached one side only, to the bottom of my plywood base. I then used my carpenters square and made sure that the stopper piece was absolutely alighed using the carpenters square and was 90 degrees to the edge of my base. I then clamped the stopper piece to ensure it would not move during the process of inserting the remainger of the screws to fasten the stopper piece to the base.
When the stopper was attached I tool the whole unit to my table saw and found the center of the 20 inch wide board. Before you cut the board in half, take a moment to MARK where you are going to cut the board in half and mark each side. I used a couple of opposing arrows. These marks to to help you remember exactly which sides of the jig need to be together for the final dado cut.
At this point I then cut the base in half, and with that the jig is basically finished.
Using the jig is about as simple as making it. You will need a "Top Mounted Bearing Router Bit" for this, some people call these dado bits, while others call them template bits and regardless what you call them do NOT confuse them with "Flush Trim Bits" which have the bearing on the bottom tip of the bit.
You will need to pre-set the depth of you cut after you insert the bit in your (unplugged) router. I usually make mine about 3/8 inch deep, which is about half the depth of a 3/4 inch board.
The jig can be used to make through dados, that is, dados that run the entire width of the board, or you can make "stop dados", those which stop before the end of the board. With a stop dado, you will need to cut out a small notch in the shelf board so it sits neatly into the dado and runs flush with edge of the board, or you can make a stop dado and have the shelves sit back from the edge, and in some cases where you might be installing doors, this would be the preferred method.
The Simple Dado Jig is a self named, handy workshop addtion, easy to make, easy to use and gives great results and many, many years of service.
Copyright Colin Knecht