How to Build a Strong Mortise and Tenon Bench
A Bench That Can Serve Many Functions
The Useful Bench
Benches have been around for some time and though all are useful, some yield more uses than others. The ideal bench is very strong; strong enough to stand on if you use it to reach something high. It is also used to sit on like it were a piece of furniture. It should also be nice looking if it is something that is kept in the home.
This mortise and tenon bench serves all of those functions. This is a simple bench that offers some challenges for the builder. These same challenges not only create an attractiveness to the bench, but also give it it's unique strength. The materials for it are easy to obtain and the outcome is stunning!
Although I have designed this bench and have never seen another one quite like it, I am hesitant to take credit for it. It's lines are very simple and there are just too many bench designs out there that haven't been seen by the masses.
When I built my first prototype for this project, I wanted to keep one thing in mind; simplicity. Simple and easy to find materials, a rather simple look, and simple finish.
The boards that I used are standard construction grade, 2 x 6 Pine lumber; the kind found at the local lumber yard. You could also use 2 x 12 Pine lumber and save yourself gluing up boards, but it's easier to find better lumber pieces without having to look too hard and it also reduces the cost of the lumber. You will need boards that are flat with no warping and no large knots.
The finish that I use produces an aged finish. The finish ingredients are brewed strong coffee, white vinegar, and a steel wool pad. If you want to take it further like I did you will add Linseed Oil and paste wax for the final enhancement. You could always opt for a painted finish or stain and varnish finish if you choose.
Let's get started!
Select Your Lumber
I start by selecting two boards for the seat. In the photo above, I found two ideal boards. There aren't any large knots and the boards are nice and straight with no warping.
This particular bench will be three feet long but you can alter the design to accommodate a longer or shorter bench as needed. I am ready to move on by putting a chamfer, (angle cut), around the top edges of both boards. The chamfer will remove 3/8" from the edge and will be at a forty five degree angle.
Cutting the Chamfers
With the table saw blade set at 45 degrees, adjust the rip fence so that only 3/8 of an inch is taken off of the edges. This not only cleans up the edges, but also takes the "construction grade lumber" look away and replaces it with a cottage furniture look.
Assembling the Seat
In the progressive photos above, you can see how the chamfers are done and the look that you get with the two boards together. With the two boards exactly the same length, you are ready to glue them together. Once the glue is dry, you are ready to move on to the next step; marking the area for the mortise. You can see where I have done this on the boards above.
Locating the Mortises
The location of the mortise will be 4 1/2" from the end of the seat planks. Because this is made of construction grade lumber, this distance ensures that there is strength and good wood between the mortise and the end of the boards. There will be a 3" space between the mortises and the mortise itself will be 2" wide by 1 1/2".
Unlike other benches that are assembled with mortise and tenon joinery, these mortises will be cut at a 10 degree angle. The angle will go from your layout on the seat and angle toward the edge of the board as you cut through the boards. This will be repeated at the other end of the seat.
Cutting the Mortises
When starting to remove wood from the mortises, you will want to have a bevel guage set at 10 degrees to check you progress. Begin by drilling several holes in the area to be removed. This greatly speeds up the process.
If you want to cut your mortises in a traditional way, you will need a sharp chisel and a mallet. Taking your time and working carefully, gradually remove wood from the mortise. Occasionally check the angle to be sure that you are maintaining the 10 degree angle.
If you own a scroll saw or a saber saw and want to speed the process, most of the wood can be removed with these tools. The seat boards are a little cumbersome to hold and handle, but it can be done. If using this method, clean out the mortise with a chisel after sawing.
Making the Legs
If you are using 2 x 6 lumber like I do, you will need to cut two boards 21" long and glue side by side. You will need another set for the other end of the bench. With the boards glued together, you will set the blade of your table saw at 10 degrees. Cross cut the top and the bottom ends with a 10 degree angle.
With this done you are now ready to taper the sides of the legs. The base will be the full 12" width and then taper to 9" at the top. Begin by marking the cut lines on the boards with a pencil. Depending on what tools you have at your disposal, you could make these cuts with a handsaw, saber saw, or a table saw.
I made a simple jig that I can use with my table saw that holds the board at the angle that I need to make the cuts.
Angling the Sides of the Legs
The legs will start at the widest point at the base where the legs are located. The actual width here will be 11 1/2". The legs will taper toward the top where they will be 9" wide at a point 19" from the base.
To cut this angle, I made a very simple taper jig to use on a table saw. As you see in the photo, this is a piece of 2 x 2 lumber that is about 25" long. Next I fastened a piece to make an "L" shape. Finally drilled a hole to accommodate a 3"carriage bolt in the 25" piece, inserted a nut into the top of the hole, and can screw the carriage bolt in and out to create the angle that is desired.
To prepare the legs for tapering I marked the cut line on the board. Next, I put a straight edge along the saw blade and adjusted the angle on the jig until it matched the needed angle.
One thing that is great about this type of project is that it is forgiving; that is, if the cut isn't exactly on the line it's still alright. This is a rather rustic piece and our forefathers used what tool that they had to construct their benches.
Finishing up on the legs
After you have your boards tapered, it is time to cut the arc that form the feet on the bottom of the legs and cut the angled mortise for the cross member.
For the arc, set a compass for 6" diameter and scribe a line. The top of the arc will be 3" from the bottom edge of the board and will leave 3" on either sides for the legs. (see drawing)
For the angled mortise, the bottom of the mortise will be another 3" from the top of the arc. The mortise will be centered on the board and will be 1 3/4" high and 3/4" wide. Make sure that you angle the mortise in the correct direction. On the outside of the leg, the mortise will angle 10 degrees upward to accommodate the cross member.
Finishing up with the top tenons
To finish up our legs, we now have to cut the tenons that will fit through the seat. The tenons will be 2" wide with a 3" gap in between. The tenons will be 1 1/2" in height so that when they fit through the mortises on the seat, they will be flush with the top.
Making the cross member
You are now ready to mill the last major piece of the bench; the cross member. Start by cutting a board three feet long. The piece should be 1 1/2" thick and 2 1/4" wide.
Next we will cut the tenons that will fit into the mortises in the legs. Measuring 3 3/4" from the end of the board, make a mark and then draw a line at a 10 degree angle that angles out toward the end. (see drawing) With a dado blade installed on your table saw, set the height of the blade on the table saw at 3/8" high and then set the miter guage on the saw at 10 degrees. Lining the blade on your mark, start removing wood and continue making passes until you reach the end of the board. Repeat on other end of board. This can also be done without a dado blade but will take a little longer to remove the wood.
Remove the dado blade and put regular crosscut blade back on the table saw. Set blade height at 3/8 ". Set the angle of the blade at 10 degrees and set the miter guage at 90 degrees. Start making passes on the top and bottom of the tenon to get the needed height to fit the mortise. Repeat on opposite end.
Smooth the saw marks on the tenons and fit through leg mortises. I also like to round the ends of the exposed tenons that will protrude on the outside of the legs.
Cutting the pins and the mortises
You are almost done at this point. With the cross member in place in the legs and the legs attached to the seat, You will need to mark the area to cut mortises for the pins. The mortises need to be right next to the legs and should be 5/8" high and 1/2" wide.
With the mortises cut, you will finish by cutting the pins that fit into the mortises. The pins will be 4" long and 5/8" wide and cut from 3/4" stock. Sand the stock, keeping it 3/4 on one end and tapering it down to 1/4".
Getting ready for a finish
This bench will hold itself together without any glue or fasteners, however, you can glue the leg tenons into the seat mortises if you choose. With everything assembled, plane or belt sand the top of the seat so that everything is flush and smooth on top. Sand all pieces until the saw marks are removed.
Construction is complete and you are ready to put a finish on your bench if desired.
Selecting a finish
As with any wood piece, you have some choices to make as far as a suitable finish. After your had work of making mortise and tenon joinery, you need to show it off. A quick and easy finish would be to stain and varnish your bench. When I build these benches, I want them to have a finish that makes them look very old and I use an ageing process on the wood to achieve this.
I begin by brewing about 4 cups of very strong coffee. I paint the coffee on the entire bench. You don't want to miss any area. Make sure every square inch gets covered. After this, I take a cup of white vinegar and put it into a glass jar. I then put a steel wool pad into the vinegar and allow to sit over night.
The following day, paint the vinegar solution on every square inch of the bench. After about 30 minutes you will see the vinegar reacting with the tannic acid in the coffee and creating an aged look before your eyes. This will produce a gray, weathered look to the wood. You could just stay with this look but I will take this a couple of steps further.
After the aging process, I will brush on a coat of Linseed oil and allow to dry over night. The following day I will rub on a coat of paste wax. This will produce a very warm but aged look to your bench. The wood will continue to grow a little darker and richer over the next month and creates a finish that you just can't obtain any other way.
The completed bench
This bench is now completed! The finish will make this piece of furniture look nice in any room in the home. This design where the legs are angled inward at the top will actually tighten up when the bench is in use. The mortise and tenon joinery is a challenge but the work pays off in a big way!
I have made many of these benches and will make many more in the future. I hope that this will be an enjoyable project for you. Enjoy!
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