Introduction: How to Make a Simple Table Leg Assembly Using Mortise and Tenon Joinery
One of the simplest traditional joinery methods is the mortise and tenon. This is a fantastic join for table legs, and with a few tools it can be extremely strong.
This is the method that I use to create table-leg bases, but there are of course lots of other ways around it.
Click here to watch the YouTube video where I make this table: https://youtu.be/faPzXCdEwCw
Step 1: Milling and Marking
The first step is to get your stock for the job. The more square and stable the wood, the better it'll work. If the wood is only recently dried try to leave a day between each milling step. This will allow the wood to move as the stresses are released.
Once your stock is cut square and to size it's time to mark out for the mortise, the holes in the legs. In this case the rail will be the tenon, so it's important that all the rails are the same size.
Using a combination square mark out the front facing edge, the face that you'll see when looking at the table. Make this the same all the way around the table on each leg. This line will be cut first because it's what people will see, any adjustments will be made on the line facing inwards.
Now draw the line on the other side to represent the width of the rail, and finally, cut along the lines with a marking knife. I can't stress how important this part is, especially if you're using a hardwood. A lot of hardwoods splinter easily so breaking the wood fibres along the line means you'll have cleaner lines.
Step 2: Removing Material From the Leg
Now that you've marked out the leg you need to remove the material. I like to use a drill press to get rid of the majority of it because it's quicker, but also because the router should be under as little stress as possible to ensure a clean cut.
Drill a series of holes using a depth stop, leaving a couple of millimetres before the line.
Now setup a stop block for the router, so you don't accidentally cut too far, and start removing along the cut line.
Setup the fence on the router so you're cutting on the line of the outside face of the rail/leg (again, start with the outside face and any mistakes can be fixed on the inside face). Do all the legs with this setting on the fence so they're all the same. Be careful cutting in both directions as the router will react differently to the feed direction. This highlights the need to remove as much material as possible using the drill press.
Once you've done all the legs with the fence in one setting, move it to cut along the other line and repeat. At this stage the rails should either be a snug fit, or not be able to fit. I would rather cut the mortises undersize and sand the rails down to fit. Cutting the mortise too big is a deal breaker.
Step 3: Cut Shoulder Into Rail
I like to cut the mortise into the leg slightly shorter than the height of the rail. This means you can cover the curved corners left by the router with a shoulder on the rail. You could square up the corners of the mortise but this is quicker and the net result is almost the same.
Cut a small notch out of the bottom of the rail in each corner, enough so that the corner sits flush against the leg and the top of the rail is flush with the top of the leg. The sharper this cut is, the better it will look, so take you time and cut all your lines with a marking knife.
Step 4: Glue Up
Now that you have a snug fit you can glue the parts together. Use a ratchet strap of clamps to pull the legs into the rail. I like to do this glue up in 2 stages so I have time to make sure that the rail is 90 degrees to the leg.
The best way to improve is by practicing and learning form mistakes. My first leg assembly was horrible, but after a lot of mistakes I'm finally at a point where I'm happy with the end product. It just takes practice.