Once your stock is at a working dimension (4 square and final length for the rails an inch overlong for the legs) it’s time to start laying out the joints that will create the base for your table. The joinery used for a good table is a haunched mortise & tenon. There are several great alternatives…but this is a good starting point.
For furniture it is important to think of the end result early on. Take a moment to arrange the pieces on your bench so you know at a glance where the true faces and edges are. Find an orientation that allows you to have the true faces and edges of the legs on the inside (where the joinery hits), and the true faces and edges of the rails up and out (allowing a seamless mating between the top and presenting a better show face on the outside). Think about the way you want the grain to run based on the tapers (which will be on the inside of the leg not outside). I like to arrange the grain to follow the taper if I have a bit of runout to use, but this arrangement reverses the typical arrangement for planing the tapers because of the grain…not a big deal but something worth bearing in mind.
Once you are happy with an arrangement mark your rails and legs with a cabinetmakers triangle. This will really aid construction of your work in the next steps. Use one triangle mark on the four legs, one for each pair of rails (3 triangles in the end). I put mine on the top of the legs (which will get cut off) and the top of the rails (where the table top hides them). Pick a direction for your triangles and stick with it. That means that the point of the triangle should always point the same way on a component now matter where it is in the piece. A logical way to do this is to have the triangles point towards the back of the piece (I typically choose the left…don’t ask why).
The layout process starts at the legs. Take your legs and make an even mark squared around the top about 3/4 of an inch from the end (this helps you mark out the horns that will aid in assembly as well as protect the piece from blowing out as you mortice near the end. The extra quarter inch on the bottom gets chewed up when you level the table after attaching the top. Next we do the most critical measurement in the whole piece…the shoulder cuts. These measurements are paramount the the final look of the piece and they are also what dictate the shape of the piece (rectangular, hopefully). Mark the shoulder length directly from your story stick, and don’t worry if the overall length of your rails is a bit off. The shoulders matter, the length of the tenons can get adjustment within the leg…if your rail is a bit long of a bit short just split the difference in length on both ends of the piece to keep things close. Some people mark the shoulders with the individual rails clamped together, I have never had good luck with this. If you use a knife to make your story stick the layout from it to each rail is dead on, so I do mine one at a time. Square the shoulder line around the end of each rail with serious care to reference from the true face and edge (always important, but forgetting this here would be disastrous enough to mention it again again).
Once you have this done you can start laying out the rest of the joint. Let’s start with the rails (tenons) since it’s easier to superimpose those to the leg (the mortise). I mark all the rails at the same time for consistently.
1. The shoulders for the rails.
2. The setback at the bottom of the rail. This is about a quarter inch and is just there to hide the end of the mortise hole in case it’s a bit irregular.
3. The Thickness of the mortice/tenon can be done and anytime. If you use a single guage, mark the thickness out one mark on all the rails, then a second mark that is taken from your chisel (I set my chisel on the rail against the first mark and made a second mark with a knife on the other side an lined my gauge up to that)
4. The haunch is about 1/4 quarter of the tenon width (from the setback to the edge use dividers to step four steps…when it lines up you have your measurement…make a tick in your work with the dividers and set your marking gauge to this setting.)
5. the haunch should only be 1/4 to 3/8th deep, mark this next. I just eyballed a divider seting and went with it.
You should end up with crisp lines that you can transfer to your mortice. Note the pencil lines where just to help show that structure of the joint but can be an aid in sawing later, since it will be your goal to remove one the half of the pencil mark that is on the waste side of the line leaving the other. Don’t mark the shoulder this way.
This is where life can get tricky. You could cut the tenon first and super impose the joint to the other…but it’s easier to fit a fat tenon to a mortise than to pare a mortice to fit a tenon. I lay everything out first but cut the mortise first. Line the edge of the rail up to the knife line at the top of the leg. The rail should set back from the leg about 1/8th of an inch. But the outside of the leg is not true. That’s OK. Find a setback that looks right and mark the back of the joint (the inside of the table with either a pen or a light marking gauge mark (careful not to go below the rails width, not fun to fix). This mark only needs to be on one leg, since you use it to find where the mortise walls go (lining up the gauge with your tenon marks after lining up your rails to your top line an back placement line). Using a mortice gauge you can just line up the marks and be on your merry way (take a second to pencil the setback mark from your rail to your leg so your gauge marks don’t go too far down the work). With one gauge I would use a different tack, I would make knife marks in the leg where the tenon cheeks are so I could drop my marking gauge into those to capture my settings…I would mark the legs with one setup of the gauge, switch set ups and mark the final marks…going back and forth with gauge settings can be bad for your health.
Finally you can take dimensions for the haunch and the setback and transfer those with a knife to your mortise. Dirty cheating trick…I only use one rail to do this on each leg, I square the other mortice dimensions by lining my square with my knife mark, nicking the inside corner of the leg, and flipping the leg over so I can use the nick mark to line the other horizontal marks up exactly the same as the other joint. The nick is on the inside of the leg so even if its too deep for a smoother to take it off no one knows it’s there.
This is the sloppiest of the four leg layouts I did but you will note I was careful not to allow any of the markings extend through the front of the work since this would be visible on the final piece. Some craftsmen layout there joints, cut them and then plane off the marks they left (Tom Fidgen does this to great effect). I prefer to be tidy with my initial layout instead. Both approaches work but I feel my way has less chance for error in effecting the squareness of the casework.
Crisp layout really helps the work come together well. Note that may lines will be covered when the joint is assembled, this is worth the extra time.
Now we can set down the knife and pick up a chisel…for those of you who like to skip ahead two key pieces of advice.
1. Cut the full depth mortice before the haunch (think about what happens to your layout line if you got the other route). Note the bit of breakout I had on the first mortice, the rail covers it but the grain of this sapele will not be forgiving to more slip-ups on my part.
2. Cut one mortice to a depth where it just touches the second mortice wall. Cut the second one to depth, this helps avoid breaking out the interior wall of the leg…saving valuable glue surface.
-- Make furniture that lasts as long as the tree - Ryan