Identifying Concealed Cup Hinges: Replacements for Blum & Hettich (35 mm Cup & System 32)
A concealed cup hinge is a hidden cabinet hinge consisting of an articulated arm and a metal cup recessed into the cabinet door. Whether working in the workshop or fitting a kitchen, replacing broken hinges or planning new cabinets often presents a bewildering range of technical specifications. Brands like Blum and Hettich have defined the market, but when it comes to successful replacement or planning, the brand logo on the metal is far less critical than the precise geometry of the fitting.
This guide provides the technical foundation for identifying the correct concealed cup hinges / cabinet hinges, interpreting dimensions accurately, and ensuring full compatibility with existing hole patterns under the System 32 standard.
Anatomy and Key Dimensions of a Cup Hinge
The hinge functions like a precise metal knee joint, guiding the door's movement while carrying the full weight of the front. It comprises three main components whose dimensions must match exactly during replacement.
The cup is set into a blind hole drilled into the cabinet door. The industry standard cup diameter is exactly 35 mm. Mini hinges with a 26 mm diameter are used only on very light or narrow doors (for example, in caravan construction or compact bathroom units). When searching for replacements, first measure the diameter of this recessed hole. For standard requirements, fitters use 35 mm concealed cup hinges.
The mounting plate (often referred to as a base plate or cruciform plate) fixes to the interior side of the cabinet carcase, establishing the connection to the hinge arm. The hinge arm connects the cup to the mounting plate and, through its crank (bend), defines how the door sits relative to the carcase edge.
The Drilling Pattern: The Key to Compatibility
When replacing an existing hinge, knowing the cup diameter alone is not enough. The fixing screws flanking the cup feature different spacings depending on the manufacturer. The most common drilling patterns (distance between screw holes / distance from screw holes to the cup centre) are:
- 45 / 9.5 mm (frequent with Blum)
- 52 / 5.5 mm (frequent with Hettich)
- 48 / 6 mm (frequent with Salice or Mepla)
Provided the drilling pattern and overlay type match, hinges from different manufacturers can be interchanged without difficulty.
The Three Fundamental Overlay Types
The most common mistake when purchasing fittings is selecting the wrong overlay type. The crank of the hinge arm determines how the closed door sits relative to the carcase side panel.
1. Full Overlay (Surface Mounted Door)
With a full overlay, the closed door covers almost the entire front edge of the carcase side wall. Only a narrow reveal of roughly 1.5 mm to 2.0 mm remains at the outer edge to prevent the door binding when opened. The hinge arm on these fittings is straight (uncranked). This style is standard for individual standalone cabinets. You can find suitable fittings under full overlay concealed cup hinges.
2. Half Overlay (Dual / Twin Application)
When two doors hinge on a single central partition panel (for instance, in a four-door wardrobe), both doors must share the front edge of the 16 mm or 19 mm thick chipboard. Each door must therefore cover only roughly half the edge. The hinge arm for a half overlay is noticeably cranked (curved) to achieve this offset. For these builds, half overlay concealed cup hinges are required.
3. Inset (Flush Door)
In this configuration, the door sits completely flush within the carcase opening, leaving the front edges of the carcase walls fully visible when closed. The hinge arm features an extreme crank. The mounting plate must be set further back inside the cabinet (typically by the door thickness plus the reveal). For these flush designs, choose inset concealed cup hinges or search specifically for concealed hinges for inset doors.
Opening Angles: From Standard to Specialised Solutions
The opening angle determines the maximum arc through which the door can swing. The choice depends on the position of the cabinet in the room and its internal layout.
Standard Angles for Kitchen and Living Furniture
For most cabinet doors, an opening angle slightly beyond 90 degrees is sufficient. The absolute standard across modern cabinetry is 110°. This angle provides convenient access to interior shelving. Corresponding 110-degree concealed cup hinges / cabinet hinges form the foundation of most kitchen layouts.
Wide-Angle Hinges for Internal Pull-Outs
Whenever you plan drawer systems or pull-out wire baskets behind a hinged door, a standard opening angle is insufficient. An open door at 110° would protrude into the carcase opening and obstruct the runner. This is where wide-angle hinges are essential. A hinge with a 155° or 165° opening angle swings the door completely clear of the internal carcase width.
- 155-degree concealed cup hinges / cabinet hinges (frequently engineered with zero protrusion)
- 165-degree concealed cup hinges / cabinet hinges
Planning note: When fitting full-extension runners behind hinged doors, always check the internal clearance. Full extension drawer runners require lateral clearance that must not be restricted by a door that does not open wide enough.
Angled Hinges for Corner Units and Slanted Cabinets
Not every cabinet carcase is built at right angles. For corner units in L-shaped kitchens, angled bathroom units, or under-eaves cabinetry, specialised angled hinges are used. Here, the degree rating refers to the carcase angle rather than the opening arc.
- 30-degree concealed cup hinges / cabinet hinges
- 45-degree concealed cup hinges / cabinet hinges
- 90-degree concealed cup hinges / cabinet hinges (often used as blind corner hinges for filler panels)
- 135-degree concealed cup hinges / cabinet hinges (typical for bi-fold corner cabinet doors)
Additional Features: Soft-Close vs Push-to-Open
Modern hinge kinematics offer two distinct, mutually exclusive operational mechanisms.
Soft-close damping decelerates the door over the final centimetres of its closing travel, pulling it gently and silently against the carcase. In modern hardware, the damping cylinder is integrated invisibly within the hinge cup or hinge arm. Soft-close concealed cup hinges / cabinet hinges are intended for doors with handles.
The push-to-open system (tip-on) is designed for handleless fronts. Here, the user presses against the door, prompting a spring-loaded plunger to pop the door ajar. Note: this function requires unsprung hinges (without self-closing springs). A soft-close hinge would fight directly against the push-to-open plunger. Never combine soft-close hinges with tip-on plungers.
Installation and Adjustment Under System 32
System 32 is an international standard in cabinet construction. It specifies that vertical rows of holes in carcase sides are spaced at exactly 32 mm intervals. The distance from the front edge of the carcase to the front row of holes is standardised at 37 mm. The standard hole diameter for shelf supports and mounting plates is 5 mm.
When replacing mounting plates, they will generally align with this 32 mm grid. When drilling the cup into the door, the standard drilling distance from the door edge to the perimeter of the 35 mm hole (the cup distance) is typically between 3 mm and 6 mm.
3D Adjustment
Once hung, doors rarely align perfectly straight straight away. High-grade concealed hinges feature adjustment screws on the hinge arm, allowing you to align the door reveals in three dimensions:
- Lateral adjustment (side-to-side reveal): The front screw on the hinge arm shifts the door left or right. This ensures the door runs parallel to the carcase outer edge and avoids clashing with neighbouring doors in half-overlay setups.
- Depth adjustment: The rear screw on the hinge arm (often featuring an eccentric cam) moves the door closer to or further from the carcase. This sets the front gap between the door and carcase, which should typically sit around 1.5 mm.
- Height adjustment: Carried out on the mounting plate. By loosening the fixing screws or turning an integrated eccentric cam on the plate, the door can be shifted vertically by several millimetres up or down.
Load Capacity: How Many Hinges Per Door?
The number of hinges required depends on the weight and height of the MDF or chipboard door front. Excessive weight will cause the door to drop and accelerate wear on the pivot joints. Use the following technical guidelines:
- Up to 900 mm height / up to 7 kg: 2 hinges
- Up to 1600 mm height / up to 14 kg: 3 hinges
- Up to 2000 mm height / up to 20 kg: 4 hinges
- Up to 2400 mm height / up to 26 kg: 5 hinges
The distance between the top and bottom hinges should be maximised to reduce leverage forces and maintain maximum stability.
Internal Cabinet Accessories
Planning kitchen cabinetry involves not only the hinges, but also the intelligent use of interior space. For example, if you install a plate rack insert for wall units above a sink, ensure the hinges offer sufficient corrosion resistance or are adjusted so the door can remain slightly open when not in use to encourage air circulation. For base units, under-mount concealed drawer runners are frequently chosen to sit invisibly beneath the timber drawer box. Here too, the cabinet door hinges must swing wide enough to clear the path of the drawer runner completely.
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FAQ: Frequently Asked Questions About Cabinet Hinges
How do I measure a kitchen cabinet hinge correctly? First, measure the diameter of the recessed cup in the door (usually 35 mm). Next, measure the centre-to-centre distance between the two fixing screws beside the cup (e.g. 45 mm or 52 mm). Finally, check how the door rests against the carcase edge (full overlay, half overlay, or inset) to determine the required hinge arm crank.
Can I replace a broken Blum hinge with a different brand? Yes, provided the core technical specifications match. The cup diameter (35 mm) and the overlay type (e.g. full overlay) must be identical. If the drilling pattern (screw spacing) differs, new pilot holes must be drilled into the door. When switching brands, always replace the carcase mounting plate as well, as clip-on mechanisms vary between manufacturers.
What is the difference between soft-close and push-to-open? Soft-close relies on a hydraulic damper that catches a swinging door and pulls it quietly shut. Push-to-open uses a mechanical release catch for handleless doors, pushing the door open slightly after a light press. Both require different hinge types: soft-close requires sprung hinges, whereas push-to-open strictly requires unsprung (free-swinging) hinges.
Why is my cabinet door no longer sitting flush? This is usually down to shifted geometry or a loosened fitting. First, verify that all screws on the mounting plate are tight. Next, adjust the depth screw (rear screw on the hinge arm) to bring the door closer to the carcase. If the door sticks out at the top or bottom, use the lateral adjustment (front screw) to restore parallel reveals.
What drill bit do I need for a standard hinge? For the cup, you will need a 35 mm Forstner bit. For the mounting plate screws in the carcase (System 32), a 5 mm wood drill bit is used for Euro screws. For standard wood screws, a 3 mm pilot drill bit is sufficient.
What does System 32 mean in cabinet making? System 32 is a standardised manufacturing convention. It specifies that vertical rows of holes in cabinet side panels are spaced exactly 32 mm apart, with the front row positioned 37 mm in from the edge. Virtually all modern mounting plates and shelf supports conform to this grid.
How much weight can a standard concealed cup hinge hold? A single hinge is not rated in isolated kilograms; load capacity comes from the complete hinge assembly. Two standard hinges will reliably support a 19 mm chipboard door up to 900 mm in height and roughly 7 kg in weight. For heavier or taller doors (such as mirrored fronts), increase the hinge count in accordance with the technical guidelines (up to 5 hinges for doors up to 2400 mm).