Monday 9 July 2018
The fit of a lid can make or break the quality of a finished box. By the time you come to install the metalware, 90% of the cost and effort has already been committed, so the last thing you want at this stage is to introduce a sloppy action or unsightly gaps.
Hinges and locks for boxes can be similar to those for cabinets – in many cases a box is essentially just a cabinet lieing on its back; but there are often more subtle differences as well. Some makers produce their own hinges as part of the furniture construction, either with showy wooden pins or with concealed metal ones. However, this article will concentrate on fitting proprietary brass hinges, locks and stays to solid wooden cases such as a jewellery box.
Butt hinges are the most familiar type, consisting of a pair of rectangular plates or leaves joined by interlocking barrels on one edge with a pin through the barrel centres. Hinges used by furniture makers are traditionally brass rather than steel because of its corrosion resistance and the ease with which it can be polished. Sturdy butt hinges are manufactured by drawing or extruding hot soft brass through a shaped die, like toothpaste squeezed from a tube. Stainless steel is available in some patterns as a good-quality option. Cheaply made hinges are pressed from sheet metal, folded around the pivot pin, but they do not perform as well or look as tidy.
Butt hinges normally have square corners but some are rounded to fit directly in the rebate left by a router, and there are even butt hinges shaped to fit in the slot made by a biscuit jointer.
When fitted, the butt hinge's plates are recessed into an opposing pair of shallow mortises in the box base and lid. The position of the pin must be centred outside the walls to allow the lid to swing beyond 90 degrees without binding. The clearance here can be as little or as large as desired, so long as there is some. Two hinges may be enough to secure the lid of a small box, but three or more will reduce the strain on a larger one. The pivot pins of all hinges must be aligned accurately otherwise they will be forced as the lid rotates.
I find it best to check out the hinge position by surface mounting the hinges with a pair of steel screws before cutting any recesses. While this only allows the lid to swing closed with a large gap at the hinge side, it does enable you to check the alignment and straightness. If things did get slightly out of line there would be an opportunity to plug and re-drill the mounting holes invisibly beneath hinge plates. When the placement is correct, run a knife line directly around the hinge plates to mark out ready for the recess.
To secure brass hinges and fittings you will need to fit brass countersunk screws into pilot holes drilled in the wood. The problem with these screws is that they are soft and easily damaged. Some are much weaker than others, depending on the quality of the alloy and machining processes. It is worth buying good ones if you can. Also ensure that the screwdriver is a perfect fit.
Shearing off a brass screw by forcing it into a tight-fitting hole is an annoying and time-consuming problem to recover from. Even if the screws do not break during assembly, too much torsion can work-harden the metal, making it more likely to break in use.
By using a matching design of steel screw for the initial fitting you can cut threads in the pilot holes ready for the softer brass ones. Wax all screws before fitting them, either with a candle or a block of beeswax.
Cutting the recess with a router is quick and guarantees an even depth, but if the router goes slightly off course the results can be disastrous. I prefer to chop out rectangular hinge recesses with a razor-sharp chisel, which probably takes no more time than setting up a router. Use a fine-marking gauge and set the depth to align with the centre of the hinge-pin so it is set to half the folded hinge thickness, then mark the recess depth.
Chop deep marks at each end of the hinge rebate and a shallow one along the grain at the back, taking care not to split the wood. Pare up to the end marks in easy stages then use a wide chisel to pare away the full width of the rebate down to the depth line.
If the hinge leaf is of the traditional tapered style you can taper the recess to match, keeping the brass leaf just below flush with the wood.
The pivot or knife hinge is sturdy but incredibly simple. It is especially suitable for fitting flat lids or doors into recessed cases. Depending on the geometry and throw of the lid as it opens, you can either buy straight versions so the pivot is in line with the lid, or L-shaped cranked versions so the pivot is outside. The L-shaped versions create a clearance while the lid swings open but are visible from outside, whereas the straight versions need the wood to be shaped to avoid fouling.
Pivot hinges come as two matching parts, one fitted with a pin and the other with a hole. Each leaf of the hinge is secured by screws in a narrow grooved rebate, channelled along the lid and the corresponding edge of the box opening.
The most familiar design of secret hinge must be the type used on fitted kitchen cabinets. By joining a series of pivoted arms, the hinge mechanism can be recessed into wood with no visible external parts when it is closed, yet it swings clear of the case when opened.
Miniature multi-leaf hinges based on this principle are made from brass and designed for fine furniture. Barrel hinges contain an intricate multi-leaf mechanism in a pair of cylinders designed to fit snugly in a pair of opposing holes, providing an 'invisible' pivot mechanism for solid wood doors and lids. A miniature bolt within each barrel allows it to be expanded and locked in place.
Unlike a vertically hung cabinet door, a box lid will not stay partially open. One solution is to allow the lid to swing right back so the wooden lid contacts the wooden base, but this can cause marking on the wood and strain on the hinges. Stays, such as a simple restraining chain, can be arranged to hold the lid just beyond the vertical position. Unfortunately, chains can easily catch in the works, so a solid brass stay, equipped with either a sliding or a cranked arm, provides a more reliable solution. Sliding stays fit into the round-ended groove cut by a router bit while cranked stays are surface mounted with screws.
Many hinges are available with inbuilt stays, the most common being quadrant hinges. These L-shaped devices are fitted on the corner of a box, where they require sufficient width in the box side to make a deep recess for the quadrant arm. It is worth checking the dimensions and sweep of the quadrant hinge at the box design stage. Brusso make small rectangular butt hinges that look quite conventional but contain an integral 95 degree stop. These ingenious devices are sturdily made, well finished and can be fitted in the same way as any other butt hinge.
Cabinet doors have catches to stop them swinging open while gravity does the same job for a box. However, a simple box lock designed to keep out intruders of the nosey variety rather than serious thieves makes a box complete and keeps it closed during transit. The box lock, unlike a cabinet door lock, has a set of hooked fingers attached to the underside of the striker plate. These pass through holes in the top of the lock. When the key is turned they are trapped by the sliding internal mechanism.
Fitting miniature lock
To fit a box lock, use the brass case as a template for marking out the rebate, scoring around it with a knife. The shape is more complex than for a hinge and is made in two stages, requiring a deep recess for the body surrounded by a shallower one for the fixing plate.
To position the keyhole the pointed central pin of the lock will mark its own centre when the lock is aligned then pressed against the wood. After drilling the keyhole, the rebate is chopped and pared out for the lock body. The lock is pressed into place before being fixed with steel and then brass screws.
It is notoriously difficult to predict how a hinge and lid will move once assembled, particularly when you fit a particular design for the first time. For that reason it makes sense to mock up the essential features of the lid and box, then fit a pair of hinges with steel screws to check it out. After testing, the hinges can be recovered for use. This small inconvenience is far preferable to finding out that the lid fouls as you first try to close a carefully finished box.