Fitting Half Overlay Concealed Hinges — Guide

August 7, 2026

A half overlay concealed hinge (also known as a twin overlay hinge) is used when two cabinet doors are hung on a single central partition of the carcass and share the front edge of the panel.

Fitting hinges to a central dividing panel requires high precision, as both doors must share the edge just like two vehicles sharing a narrow lane. Whilst a regular full overlay door covers the entire carcass side thickness, with a half overlay the door only covers half of the edge. A defined gap remains in the middle to prevent both doors from colliding when opened.

This guide explains the professional preparation, drilling, and adjustment of half overlay concealed hinges. It is designed for fitters and experienced joiners who need to achieve precise reveal lines on multi-door cabinet fronts.

Technical Principles: The Crank

The essential difference between hinge overlay types lies in the geometry of the hinge arm. A hinge for a full overlay is generally straight (0 mm crank). A hinge for a half overlay features a medium crank of approximately 9.5 mm. This bend in the hinge arm ensures that the door steps inwards, leaving roughly 7 mm to 9 mm of the centre partition exposed (based on standard panel thicknesses of 16 mm to 19 mm). For completely inset fronts, an inset concealed hinge with a large crank (approx. 16 mm) is used instead.

Required Tools and Materials

To ensure clean installation and drilling for 35 mm concealed hinges, the following equipment is required:

Drill or powerful cordless screwdriver
Forstner bit (Ø 35 mm) with a centring tip
Wood drill bit (Ø 3 mm or 5 mm, depending on the mounting plate)
Pozi screwdriver or bit (PZ2)
Marking tools: pencil, try square, tape measure, or vernier calliper
Bradawl or centre punch to mark screw locations
Matching concealed hinge complete with cruciform mounting plate
Chipboard screws (typically 3.5 x 16 mm, countersunk)

Time required: Approximately 15 to 20 minutes per door when measuring manually.

Step-by-Step Installation Guide

Step 1: Mark Positions and Calculate the Cup Distance

Before drilling, precise positions must be marked on the inside face of the door. The distance of the hinges from the top and bottom edges of the door is usually 100 mm to 150 mm in standard cabinetmaking. It is vital to ensure that the hinges will not collide with fixed shelves or internal pull-outs inside the carcass.

Draw a horizontal line at the chosen position using your try square. On this line, mark the C-dimension (cup distance). The C-dimension defines the distance from the door edge to the edge of the 35 mm hole. For most hinges, this measurement is between 3 mm and 6 mm.

Calculation example: With a C-dimension of 4 mm and a 35 mm cup diameter, the centre point of the hole is exactly 21.5 mm from the edge of the door (4 mm + 17.5 mm). Mark this point firmly with the bradawl.

Step 2: Drill the Hinge Cup Hole

Secure the Forstner bit in the drill chuck. Place the centring tip exactly on your punch mark. Drill perpendicularly into the inside of the door.

The required drilling depth for standard hinges is 11.5 mm to 13 mm. Always verify the panel thickness of the door (usually 16 mm or 19 mm) to avoid breaking through to the visible front face. Ideally, use a depth stop or mark the depth on the drill bit using masking tape. Blow the hole clean of dust afterwards.

Step 3: Insert and Fasten the Hinge

Place the hinge into the drilled cup hole. Align the hinge arm precisely at a 90-degree angle to the door edge using a try square. If the hinge sits crooked, the door cannot be aligned accurately later.

Mark the positions for the fixing screws through the holes in the hinge cup. Prick the hole locations lightly with a bradawl and secure the hinge using the chipboard screws (3.5 x 16 mm). Use a PZ2 bit and keep the cordless screwdriver torque low to avoid stripping the thread in chipboard or MDF.

Step 4: Fix the Cruciform Mounting Plate to the Centre Partition

Next, fit the mounting plate to the carcass partition. In twin installations, the mounting plates are often fixed directly back-to-back on either side of the partition panel.

The standard distance of the fixing holes from the front edge of the carcass in System 32 is exactly 37 mm. The height of the mounting plate must correspond precisely to the height of the hinge arm fitted to the door. Mark the hole positions, pilot drill lightly with a 3 mm wood bit (or 5 mm for Euro screws), and secure the mounting plate.

Step 5: Hang the Door

Modern fittings feature clip-on technology. Hold the door up to the cabinet carcass. Hook the front of the hinge arm onto the front lug of the mounting plate, then press the back of the arm against the plate until it engages with an audible click. On older models or basic slide-on hinges, slide the arm onto the plate and secure it with a fixing screw.

Step 6: 3D Fine Adjustment

Once both doors are hung on the centre partition, the gap between them is usually uneven. Concealed hinges / cabinet hinges offer three adjustment axes directly on the hinge arm:

Side adjustment (overlay): The front screw on the hinge arm. Turn this screw to move the door left or right. This regulates the gap between the twin doors. The reveal should be a consistent 2 mm to 3 mm.
Depth adjustment: The rear screw (often an eccentric screw). It moves the door closer to or further away from the carcass. Adjust the depth so the door sits flush against the carcass without rubbing against the edge when opening.
Height adjustment: Loosen the mounting plate fixing screws slightly (or turn the eccentric screw on the plate if present) to shift the entire door up or down by ± 2 mm. Retighten the screws securely afterwards.

Common Mistakes When Fitting to Centre Partitions

Incorrect hinge type selected: The most frequent mistake is confusing overlay types. If a full overlay concealed hinge is fitted to a central dividing wall, the first door covers the entire partition edge. The second door can then no longer be fitted. Always double-check the crank beforehand.

Fixing screws colliding: If you screw two cruciform mounting plates at the exact same height on a 16 mm partition wall, the screw tips can hit each other in the centre of the board, causing it to split. Solution: Use asymmetrical mounting plates or offset the drilling heights for the left and right doors by a few millimetres. Alternatively, special through-fixing Euro screws can be used to clamp both plates at once.

Overlooking the opening angle: Standard hinges open to 95° or 110°. If you work on a central partition that houses internal full extension runners or drawers, an open door may project into the drawer path. In these cases, zero-protrusion hinges or hinges with a wider opening angle (e.g. 155°) must be used. A standard 110-degree concealed hinge is entirely adequate for standard internal shelves.

FAQ – Frequently Asked Questions

Can I replace an old hinge with a soft-close version? Yes, provided the cup diameter (usually 35 mm) and the overlay type match. Swapping them for soft-close concealed hinges is straightforward. For lightweight doors, replacing just one of the two hinges with a soft-close variant is often sufficient. Note that soft-close hinges cannot be combined with push-to-open mechanisms because the spring systems work against each other.

How many concealed hinges do I need per door? The quantity required depends on the height and weight of the front panel.

Up to 900 mm height / 4-6 kg: 2 hinges
Up to 1600 mm height / 12-17 kg: 3 hinges
Up to 2000 mm height / 17-22 kg: 4 hinges
Up to 2400 mm height / from 22 kg: 5 hinges

What is System 32? System 32 is an international standard in cabinetmaking. It dictates that rows of holes in a carcass are spaced exactly 32 mm apart, with the front row positioned 37 mm from the front edge. Virtually all modern mounting plates are standardised to this grid.

Related Products and Categories

To find the appropriate hardware for your cabinet project, review the technical requirements of your specific overlay setup. Beyond twin overlay installations, other carcass configurations require dedicated opening angles or cup sizes.