Hello and welcome to my blog! This post completes a series in which I’m building a low chair and table of Honduran mahogany for an outdoor tea house. In the previous post the tea house table neared completion and I left off with a photo of brass plates that I had ear marked for use as shoes for the table and chair.
I chose a form of brass known as ‘Naval’ brass for this particular purpose, being that this set is staked for outdoor use. Naval brass differs from the much more common 360 brass and 385 architectural bronze in a seemingly subtle way, it is alloyed with tin to make the material more corrosion resistant. The addition of tin would also seem to make the material much more difficult to machine. I learned something in using naval brass; never use naval brass where 385 bronze will work.
The brass was machined from raw stock into neatly surfaced bars. I drilled and tapped the shoes for thumb screws used as adjustable feet on the table, this will allow the table to be leveled out on the deck surface. I opted not to use adjustable feet on the chair, wanting instead a larger bearing surface than could be provided by thumb screw feet.
To complete the foot installation, they were seated into their respective bridle joints, then pinned in place. The pins are tapered square pins, when seated they pull the joint tight. After seating them into place, the ends are chamfered using a paring chisel known as tsuki-nomi.
I detailed the exposed end grain surfaces on the table with a chip carving, this carving creates a nicely textured surface. The detailing was performed with a gouge in the fukamaru shape.
The table is now completed:
Now that the table was completed, I could turn my attention back to the chairs. The base I designed for these chairs is a type of sled base with legs dovetailed into the seat pan.
Sliding dovetails alone, regardless of how tightly fitted they are, are really not strong enough to keep chair legs from racking. I debated other methods, such as utilizing tenons, and ultimately decided against having joinery show through on the seat surface or relying upon tenons which may only protrude a short distance into the seat. Instead I decided to reinforce the legs with a support similar to the bridle joined stretchers one might see under a table.
Bridle joints, however tightly they are fitted, do not offer suitable support against racking on their own and without the use of a stretcher. Rather than use bridle joints I opted to use a type of joinery which could be pulled tight, compressing the fibers of the legs and offering real support as the chair went through seasonal change and possible shrinking of the components, along with the strains applied by regular use.
To further complicate matters I wanted the joinery to be captured on one end and open on the opposing face. The open side, allowing for wedge to drive the joinery apart and enable disassembly. The closed side to keep the pin from separating the joint during assembly. I had two methods available to me; the first being a simple tongue and groove and the second a sliding dovetail.
Next, mortises were sawn into the legs to receive the supporting crossmember.
The dovetail housing was then cut into the seat pan, and the parts then test fitted.
This photo reveals the network of sliding dovetails used to support the base. The dovetail housings would be hidden away by heavy shaping of the seat pan on the underside.
Once the supporting members are seated in place, the dovetailed crossmember reveals its joinery at the seat edge. I did not want readily exposed dovetail housings at the side of the chair, being that efforts were being made to hide the housings of the leg joints.
A plan began to form, one which allowed me to hide the joinery, support the chair arm and utilizing the supporting crossmember to further strengthen the arms. Chairmaking after-all is putting all of the minor components into play in a complete network, fully utilizing each piece.
The planned joinery was laid out:
Next I began cutting the seat for the arm supports.
I then laid out the joinery to be cut onto a roughed out arm support.
The joint would be my take on what’s called a ‘Maloof Joint’, which is a bridle joint supported through the center. In the case of a Maloof joint, it uses screws that engage the seat which are then plugged with dowels. My modification of this joint uses a tenon in the center of the joint, and a self-wedging engagement to the supporting crossmember.
The mortise was chopped into the support to receive a through tenon.
Marks were transferred to the seat, which was then cut to form a tenon.
Finally the arm support was seated into position. After which, I removed it, then shaped the support, still roughly, to form a tenon at it’s top end.
Next, I marked out the tenon location on the chair arm. Noting that as the chair arm engaged the support, it’s location would change. The location was marked out with a pencil compass in its seated location.
At this point all of the joinery was cut out, my attention returned to the chair base components. The chair base was still requiring the newly machined shoes to be installed. I determined that my best approach would be to install a spline into the base of each leg, then attach the feet to that spline. This offered support to the legs, helping to keep them flat over the course of seasonal changes while providing side grain which the feet could be screwed into. The splines were captured with a set of riven pins. The pins are located 4″ apart, rather than using a single pin which concerned me to some degree.
Prior to assembling the chair I drilled the base support in part of a process known as draw-boring. The hole in the tenon is offset, slightly, from that of the mortise sides. This off-set, when pinned, cinches the joinery together and permanently locks it in place.
The pins utilized must be very strong so they are riven from straight stock. A dowel plate, which is a simple brute force mechanism is used to create short dowels. One simply hammers straight grained stock through a hole cut into the metal plate. Amazingly enough, a dowel is produced by this brutal method and that dowel is strong enough, having been riven into shape, to endure the bending forces applied as the joinery is drawn tight.
Pinning a draw bored tenon, quite literally causes the pin to bend as it passes through the joint and pulls tight the assembly.
As the chair was assembled, chamfers were cut on all of the parts, and those parts were carefully detailed to ensure that all sharp edges had been removed. Every surface was flushed or shaped by hand plane or chisel to ensure that the chair will weather well. Some parts were glued into position, others were pinned using bamboo “nails”.
The final finish was applied to the chair seat using shi-ho-sori-ganna.
The chair, when viewed in it’s side profile, reveals the curved spindles.
The prototype chair, which I will keep in the shop to reference from, was also completed. This chair was designed without arms, though now I’m certain that I would have liked an arm chair for my own use as well.
The chair and table, now completed, have been installed into the tea house, where they will be used once the weather begins to improve, or should I stay, remains improved. The Tea House is currently winterized. Thank you for following along with this build, and I look forward to your comments.