The Central Park Beam Bench: Part 2- Construction

With the sanding complete, it's time for construction of the reclaimed wood beam bench. As I discussed last time, the bench will have two legs splayed out at an angle from the top. The legs will be connected to the top with mortise and tenon joinery, which is a very strong joint. This is important, even with thick wood like this, because the legs will not be perpendicular to the top and hence will act as a lever. The joint will need to be extra strong to resist the temptation to pull out of the top. A solution to this problem would be to run a stringer (wood or metal) between the legs to hold them together. But that would distract from the look of the bench and with the thickness of this wood, I think I can get away with a mortise and tenon joint.

They aren't making any more of this reclaimed wood, so Norm Abrams' advice to measure twice and cut once is especially sagacious. I took my time calculating the angles and measuring the cuts (and double checking my calculations) to make sure everything would be perfect. All four angles of the leg cuts need to be identical, so the legs will sit at the same angle relative to the top and relative to the floor. Otherwise, the bench will not be level, it will not enter the top squarely nor will it be stable upon the floor. The cross cut jig shown below slides on the surface of the table saw and ensures a stable and precise cut.

Because of the thickness of the wood, and the fact that when cutting at an angle the width of the wood is thicker (because you're not cutting straight through) I had to make the cuts on both sides of the legs and then sand the surface. You'd need a huge saw blade to make this cut in one pass!
Although the legs would be splayed out at an angle from the top, the mortise would fit into the top at a perpendicular angle. This is for strength, but also because measuring and drilling out a mortise at an angle would be very difficult. The pieces below show the angle the legs will sit on the top and the dimension of the large tenons. They're going to be a full two inches into the top.The tenons will need to be cut mostly by hand.
Removing the top section above the tenon. Note that unlike the bottom of the legs (which I cut all the way through, above) the top of the legs need to be cut at the same angle, but the angle cut needs to stop at the tenon...
... so that the tenon emerges from the leg at a right angle to the top and that the rest of the leg, into which the tenon is a part, is parallel to the bottom cut of the leg. In other words, the leg becomes a parallelogram (or actually a rhomboid to be precise), with a tenon sticking out of the top at a right angle to the top plane. Who said geometry wouldn't ever come in handy?
To cut the mortise, I'll drill out the section to be removed with a drill press and then square it up with a chisel. I'm using a forstner bit, which is designed to make precise wood cuts, and is far preferable to the common spade bit for this type of application. I set the depth gauge of my drill press so that every hole I drill will be two inches deep, same as the length of my tenon.
The mortise completed. Notice I had to sand down the bench as the board was slightly warped, and I wanted to make sure the legs would lay flat on the bottom of the bench.
Glue applied to the tenon, ready to be inserted into the mortise. Be sure to dry fit the joint to make sure it fits snugly! I'm using Gorilla Glue which will provide a super strong bond.
And the leg, clamped in place.
Stay tuned for final sanding and finishing!