Wednesday 11 July 2018
This project gives you the chance to polish up many techniques as it involves dovetailing, coopering and inlaying, as well as lining and hardware fitting. The reward is a classic mahogany treasure chest with an arched lid, a mother of pearl inlay and a velvet lining that will undoubtedly become a treasured family heirloom.
I will briefly describe the construction before explaining the methods of assembly in more detail. The lid of the box has a coopered panel set in a frame with straight grooves front and back, and curved grooves on each side. The base of the box is a flat, plywood panel, framed in straight grooves.
The frame of the lid and that of the base of the box, are formed together with dovetails joining front to sides and sides to back. After the glue has set on these joints, the lid and base are sawn apart then fitted with hinges and a lock to fasten them together again. This method guarantees that the wood figuring and shape of the lid and base match one another perfectly.
Inside the base are compartments separated by thin mahogany dividers, halving-jointed where they cross. Foam pads covered in velvet, line the base of each section. A drop-in tray, divided and lined to take smaller items, sits high in the base and projects into the lid when it is closed.
For centuries, mahogany was the fine furniture buyer's number one choice, and the maker's first choice too, because of its superb working qualities. The real stuff (Swietentia macrophylla) from Central America or Cuba, is a treat to work with. Unlike some woods, it will never argue with sharp blades. Provided you guide your tools straight, mahogany will cut straight – no excuses! Sadly, this exquisite timber has been felled to excess, often wasted on mass-produced furniture with a short lifespan, so now there is very little available. If you get the chance to rescue any mahogany, it is well worth recycling.
A number of different woods has been sold under the name of 'mahogany' in recent years. African mahogany is a different species that looks similar but does not behave so well; the grain can become woolly after cutting. Other red tropical woods such as meranti and sapele look pleasant enough but, having heavily interlocked grain, they will not work like mahogany. Having said that, all these woods are worth saving and with some work, they can be brought to a good finish.
Coopering is a method of making a curved panel, similar to the way a barrel is constructed. Having prepared a 12mm- (1/2in) thick board, it must be cut into eight equal-width strips. The strips will be re-joined edge to edge, but first they must be bevelled at an angle of around 88 degrees. You will need to make a pair of concave formers to hold the strips in position, each strip slightly tilted from its neighbour while the glue sets. The formers must be concave so the strips sit inside the curve and the clamping pressure pushes them together, rather than springing them apart. Pull the mahogany strips together with strap clamps around the formers.
With the glue set, the panel will be shaped as a series of straight sections. To turn it into a curve, you must carefully plane away the protruding outside edges of the joints. You can do this with a finely set smoothing plane, tilting the sole with successive strokes so as to fair the surface into a curve. The inside surface of the panel needs to be shaped with a convex soled plane to produce a smooth curve inside the lid.
You need to rebate the edges of the panel ready for fitting into the grooves in the frame. I used the router table for this. Tilt the curved panel so the point of contact with the table is always in line with the router bit as is passes along the fence. The front and back of the box have angled grooves to accept the tilted edges of the arched lid. You can make these on the router table, tilting the wood at the appropriate angle from the table as it passes along the fence. Use a hand-held router to cut the arched grooves in the sides of the box, ready to receive the curved edges of the lid. Use the router's sliding fence as a trammel arm with an offcut of wood fixed to it.
Pivot the wood so it rotates about a screw, fixed to the bench. Trial fit each edge of the lid into the matching groove then mark the front, back and sides so you know which fits where.
You can use any method of construction for the dovetail joints. A router jig, provided it is fine enough and the spacing is adjustable, will do an excellent job. Bandsawing dovetails is successful, reasonably fast and, once you have made the angled wedges for positioning wood on the bandsaw table, it takes very little set-up time.
Then there are good old hand-cut dovetails worked with a fine backsaw and chisel. While certainly the slowest method, this gives you the most control and, many would say, the finest results.
You need variable spacing for the dovetails because making the lid and base in one assembly then sawing them apart, means you need to leave wider sockets between the tails at the level where the lid joint will occur. Trial fit the dovetailed box corners by partially engaging the joints then, if all fits well, glue-up the four sets of dovetail joints with the curved top panel and flat base panel trapped in their grooves. Make sure the panel has some clearance across the grain to allow for seasonal movement. Ideally, the panel lip should fit in the groove tightly enough to prevent rattling but not so tightly as to limit expansion and contraction with changes in humidity.
However, if the panel does rattle, apply a spot of glue to the centre of each curved groove, holding it, but still allowing the edges of the panel to move. Separate the lid from the base using a bandsaw – if it has a large enough throat – or a panel saw. Clean up the sawn edges using a finely set hand plane, laying the lid on the base between final strokes to ensure a good fit with no gaps.
Select brass butt-hinges and, if they are oxidised, brighten them up with steel wool before fitting. Fold the hinges over backwards and lay them on the rear edge of the box with the pivot pins just outside the wooden edge. Mark around the hinge plates with a knife or scalpel.
To cut rebates for sinking the hinge plates, use a hand-held router with a small bit. It is steerable and produces a good, level base but do not attempt to run the router right up to the edges or corners of the rebate as the motion will not be straight enough. Instead, use a fine, sharp chisel to chop back from the routed area to the edge lines.
Fit a sliding stay in one side edge of the box base to hold the lid up. These come with curved ends specifically designed for fitting in routed slots. Use the router's sliding fence as a guide while you make successive passes, plunging just deep enough for the body of the stay. A carefully positioned hole in the edge of the lid receives the button on the end of the slide and it is glued in place with epoxy resin.
Mark around the box lock then chop and pare out a socket to sink it into. This work needs to be done extra carefully because you could easily mark or damage the box front. I lay a thick towelling cloth on the bench to avoid dinging the mahogany.
The striker plate for a box lock has a pair of hooks that are trapped in the body when the key is turned. You can use this feature to align the striker plate on the lid. Trap it in the base and close the lid firmly to leave locating marks on its underside.
After fitting the box lock, drill out and shape a piece of mother of pearl to act as an escutcheon. Use a square of the material and set it at 45 degrees to form a diamond shape. You will need fine files and a fretsaw for the shaping work, but the gleaming material behaves well and is quite easy to shape.
Mark around the escutcheon with a knife line then chop a shallow rebate with a chisel around the keyhole to receive it. Epoxy resin is the best adhesive for fixing inlays like this, but be sparing with it so there is no chance of it oozing out onto the surface.
Pare a shallow socket in the lid to receive mother of pearl inlay and seat four more mother of pearl squares in the socket, taking on the curvature of the lid. These are also fixed with epoxy resin, making the finished inlay into a larger diamond emblem.
The jewel tray partitions are made from strips of 6mm (1/4in) mahogany, cut accurately to length so they fit in the length and width of the box. Use a bandsaw and chisel to make 6mm-wide slots halfway through the width of each piece at the points where it crosses other pieces. These slot together, forming halving joints, locating the dividers in a rigid cell structure.
Glue velvet over pads of stiff foam using a flexible aliphatic resin or PVA, to make a lining for each compartment of the box, then glue each pad onto the base. To make a slotted ring holder, use three strips of foam in two layers. The lower layer is a single, full-width strip while the upper one is two half-width strips side by side. The velvet is glued around the strips, tucking into the slot between the upper two, making a secure place to store rings.
Traditional mahogany and inlay calls for a traditional shellac polish finish. To create a high gloss, you must fill the grain before polishing or, for a more natural look, leave the grain open. After several rubbings of shellac, lightly followed by steel wool when dry, beeswax polish will brighten the surface.