A bisagra oculta — also called a cup hinge or European hinge — is mortised into the back of the door: a 35 mm cup is bored into the door, the hinge body sits in it, and a mounting plate fixed to the carcass carries the arm. Nothing is visible when the door is closed.
The cup and the plate
The 35 mm cup is the industry standard, bored 11–13 mm deep and set 3–6 mm in from the door edge. A smaller 26 mm cup exists for narrow doors and for frames too thin to take a 35 mm bore. The cup position — the distance from the door edge to the cup edge — is what defines how much of the carcass the door covers.
The mounting plate is the part that decides overlay. A full overlay plate pushes the door out to cover the whole carcass edge; a half overlay plate mounts closer to the panel centre so two doors can share one. Fitting the wrong plate is the single most common reason a door will not sit flush, and no amount of hinge adjustment fixes it.
| Tipo de plato | Door covers | Uso típico |
|---|---|---|
| Superposición completa | Whole carcass edge | Standard frameless runs |
| Media superposición | Half the edge, shared | Two doors on one panel |
| Recuadro | Nothing — door sits inside | Framed cabinets with inset doors |
Adjustment, in three directions
Vertical — the plate has slotted screw holes, so the door moves up or down on the carcass. Horizontal — a screw on the hinge cup moves the door left or right. Profundidad — an eccentric cam on the arm sets how far the door stands off the carcass, which is what you adjust when a door is proud at the top and tight at the bottom.
A door that will not close usually needs depth adjustment, not force. A door with an uneven gap along its length is a carcass squareness problem, not a hinge problem.
How many hinges, and where it fails
Two hinges for a door up to about 900 mm high, three up to 1600 mm, four up to 2000 mm, five above that. Doors wider than about 600 mm need an extra hinge regardless of height, because the load is off-centre.
The failures are predictable: a cup bored too close to the edge splits the door face; screws into particleboard strip and cannot be re-tightened in the same hole; and too few hinges let a tall door sag at the top corner a year after installation. Use the correct screw for the board, and if a hole has stripped, move the plate 10 mm rather than filling the hole.
Preguntas frecuentes
What is the standard cup size?
35 mm diameter, bored 11–13 mm deep. A 26 mm cup is used for narrow doors and thin frames.
Why will my door not close flush?
Usually the wrong mounting plate for the overlay type. Check that full overlay doors have full overlay plates before adjusting anything.
How many hinges does a 2.1 m door need?
Five. Up to 900 mm takes two, up to 1600 mm three, up to 2000 mm four, and anything above 2000 mm five.
Can a stripped hinge screw hole be repaired?
Move the plate 10 mm and drill fresh holes. Filling a stripped hole in particleboard rarely holds under door load.
