Creating joinery with a router
Learning how to fasten wood together is critical to almost any wood working project you take on. Today I will go over some of the more common types of wood joints and how to create them using a basic wood working router and some bits.
You have a number of choices for the joinery that you choose for any given project. You have to consider the situation before deciding which one to use. How much stress the joint will be subjected to, the final look of the joint and glue area should all be part of determining what joint to use
Selecting a joint that is going to maximize strength is important. This is determined by the amount of glue surface of the joint and the direction of any stresses the joint will experience.
Used when making book shelves or other frames a housed dado is the most common joint. It is simply a flat bottomed groove in a piece of stock.
Use your wood router with a straight cutting bit and a straight edge to guide the router is the simplest way to mill a housed dado. Simply clamp the straight edge to the board as a guide for the router base plate. You will have to determine the proper distance from joint that you will need to set your straight edge. Measure the radius of the router base plate and subtract the radius of the bit you are using. This will give the exact distance from the joint your straight edge will need to be clamped.
Once your straight edge is clamped in the proper position simply guide your router through the cut. Take several passes, increasing the depth of the cut with each pass. This way you are able to control the router easier and reduce the work load on the router. Continue to cut and reposition your straight edge until you have cut all the dados.
Ideal for shelves or bookcases that don't have a face frame a stopped dado hides the joint to make a project look better. Stopped dados are created the same way you would make a housed dado. Great for shelves and bookcases without face frames a stopped dado allows a woodworker to hide the joint along the front edge. This still provides the strength of the dado joint but stops just short of the front edge.
To make a stopped dado simply mark the joint about an inch from the front edge and stop the router as you get to that mark.
A rabbet joint is simple a groove or dado that is cut along the edge of a piece of stock. The simplest way to form a rabbet joint is to use a rabetting bit in your router. This is a straight cutting bit whose depth of cut is controlled by a guide bearing. Depending on the size of the rabbet you can change the size of the guide bearing.
Rabbets are most common for making a recess on the back of a project to receive a plywood back.
Tongue & Groove Joint
A tongue and groove joint consists of a flange on one piece of stock and a groove on a mating piece. The flange fits snuggly into the groove and creates a very strong joint, especially when glued.
It is more work creating a T&G joint then it is a rabbet or dado but provides a lot of strength and is quite stable. The groove is best formed with a router, router table and straight cutting bit. You should create a groove that's width is roughly 50% of the thickness of the stock. So with 1" stock your groove should be about 1/2".
Begin by setting up your router in the router table and set the height of the straight cutting bit about 1/16" higher then the length of the tongue. Set up the fence on the router table so you can center the groove. feed the stock through and turn it end for end and feed it through again. This will center the groove on your stock.
With the groove milled in the first piece you can measure the exact width and start to form the tongue. This is simple, place the piece with the groove flat on the router table and set the height of the bit so it is just shy of the groove. This will be the most precise method for getting the tongue the right thickness. Make the pass on the first side flip over the board and make a second pass to complete the tongue.
The four types of joints described above will be used most often in day to day wood working. They will likely make up the majority of simple joints that you make. With all the joints above gluing and clamping the stock together will create a joint stronger the surrounding wood and make for very stable projects.