Piano hinge

Overview

A piano (continuous) hinge is a barrel hinge that runs the whole length of the door, lid or panel it supports. It is made from long strips of two leaves with many knuckles and a single pin, usually pre-drilled with screw holes. It suits fall-fronts, long lids, tool-chest flaps, workbench lids and anything where a pair of butt hinges would concentrate load on two points.

Types and sizes

• Open width: 1 in (25 mm), 1-1/2 in (38 mm) and 2 in (50 mm) are the usual steps.
• Leaf thickness is the strength: thin leaves for light boxes, thicker for heavy lids.
• Hole patterns: pre-drilled on a pitch of about 2 to 3 in (50 to 75 mm), with countersunk holes.
• Materials: zinc-plated steel is the cheap everyday one; brass for visible furniture; stainless for damp or outdoor use.
• A pin that can be withdrawn lets the lid come off; a rivetted pin does not.

Where it is used

Not tied to a style: it is a workshop and utility hinge. It appears on tool chests, fall-front desks, sewing boxes and cabinet lids. It is not used in period case furniture, which hung lids on butts or back-flap hinges instead.

Choosing and sizing

Cut the hinge a few millimetres shorter than the edge so the ends do not catch. Use a width so the leaves leave at least 3 mm (1/8 in) of wood around the screws. For a lid heavier than 10 kg (22 lb), choose a thicker leaf and add a lid stay. Match the metal to the screws.

Installation

1. Cut with a hacksaw or a metal-cutting blade; file the cut end, and tap the pin back in or fit a new short pin.
2. Surface mount: drill pilot holes in the centre of each slot, 2.5 mm (3/32 in) for a No. 4 or 6 screw in hardwood, and drive each screw by hand to avoid burring the brass or stripping the plating.
3. Mortised: rout or chisel a recess to exactly the leaf thickness so the knuckle sits on the box edge and the lid closes with a hairline gap.
4. Fit the hinge to the lid first and clamp the lid in place before fitting the box leaf, using a spacer for an even gap.
5. Leave out every other screw until you are sure the alignment is right.

Wood movement and species

A long continuous hinge cannot follow a long board's seasonal change across its width: a wide solid lid fixed along its whole length with the grain running across the hinge will pull on the screws as it moves. Run the grain of a solid lid parallel to the hinge, or use plywood or a framed panel. Steel hinges and screws stain white and red oaks (White oak, Red oak); use brass or stainless there.

Common mistakes

• Hinge cut too long and ends rubbing: trim the length, not the gap.
• Binding because the box and lid mortises are not both exactly the leaf thickness.
• Screws too long for a 12 mm (1/2 in) box wall and poking through.
• Left with sharp cut ends: file or dress them.

Related

• Butt hinge: two-point alternative for a door or lid.
• Back-flap hinge: for table leaves.
• Wood screw: sizing and pilot holes.