Housing connectors—also known as funnel connectors or cup connectors—are among the most robust connecting solutions in modern cabinetry. Their conical wedge locking mechanism delivers exceptional pull-out resistance and vibration stability, making them the preferred choice for high-end custom furniture, thick-panel applications, and heavy-duty commercial cabinetry. But their performance depends entirely on correct sizing: the wrong housing diameter, screw length, or panel compatibility will compromise the entire connection.
This guide provides a systematic approach to housing connector sizing based on panel thickness, load requirements, and application type. Drawing on 15 years of manufacturing experience supplying connectors to furniture makers across 40+ countries, we cover every sizing consideration from housing diameter to CNC tooling requirements.
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Understanding Housing Connector Dimensions
Key Dimensional Parameters
Housing connector sizing involves multiple interrelated dimensions. Understanding each parameter is essential before selecting a specific model.
Primary Dimensions:
| Parameter | Description | Impact |
| Housing outer diameter (D) | Diameter of the housing body that fits into the panel bore | Determines bore size and panel compatibility |
| Housing depth (H) | Depth of the housing body embedded in the panel | Must not exceed panel thickness minus safety margin |
| Screw thread diameter (d) | Diameter of the conical tightening screw | Determines pull-out force and torque requirements |
| Screw length (L) | Total length of the tightening screw | Must match panel thickness and housing depth |
| Connecting bolt length | Length of the bolt linking both panels | Determined by combined panel thicknesses |
| Flange diameter | Diameter of the housing flange that sits on the panel surface | Affects surface appearance and load distribution |
Complete furniture connector specifications
Housing Diameter Classes
Housing connectors are available in several diameter classes, each suited to specific panel types and load requirements:
| Diameter Class | Housing OD Range | Typical Bore Size | Best For |
| Small | 8-10mm | 8.2-10.2mm | Thin panels (12-15mm), light loads, decorative furniture |
| Standard | 12-15mm | 12.2-15.2mm | Standard panels (16-18mm), general cabinetry |
| Large | 18-20mm | 18.2-20.2mm | Thick panels (22-25mm), medium-heavy loads |
| Heavy-Duty | 25mm+ | 25.2mm+ | Extra-thick panels (25-30mm+), heavy commercial use |
Panel Thickness Compatibility
Minimum Panel Thickness Requirements
The panel must be thick enough to accommodate the housing body with adequate remaining material for structural integrity.
Panel Thickness Guidelines:
| Panel Thickness | Compatible Housing Class | Remaining Panel Behind Housing | Suitability |
| 12mm | Small (8-10mm) only | 2-4mm | Light-duty only, decorative |
| 15mm | Small to Standard (10-12mm) | 3-5mm | Light to medium applications |
| 16mm | Standard (12mm) | 4mm | General cabinetry, most common |
| 18mm | Standard to Large (12-15mm) | 3-6mm | Standard cabinets, good all-rounder |
| 22mm | Large (15-18mm) | 4-7mm | Medium-heavy applications |
| 25mm | Large to Heavy-Duty (18-20mm) | 5-7mm | Heavy cabinets, recommended minimum for housing |
| 30mm+ | Heavy-Duty (25mm+) | 5mm+ | Commercial, max load |
Critical Rule: Never use a housing connector where the remaining panel thickness behind the housing bore is less than 3mm. Below this threshold, the panel risks blowout during installation or splitting under load.
Connector solutions for all panel types
Thick Panel Applications (25mm+)
Housing connectors truly excel in thick-panel applications where other connector types struggle. The conical wedge locking mechanism generates proportional holding force—thicker panels allow larger housings, which in turn provide exponentially greater pull-out resistance.
Why Housing Connectors Excel in Thick Panels:
| Factor | Housing Connector | Cam Lock | Euro Connector |
| Pull-out force (25mm panel) | Very High | Medium-Low | Medium |
| Panel utilization | Full thickness engaged | Surface-only engagement | Partial depth |
| Load distribution | Radial expansion across bore depth | Point loading at cam | Thread shear in panel |
| Vibration resistance | Structure-locked | Friction-dependent | Thread-dependent |
| Multiple disassembly | Maintains strength | Degrades | Degrades |
For panels 25mm and above, housing connectors with 18-25mm housing diameters provide locking strength that no other connector type can match.
Screw Length Selection
Matching Screw Length to Application
The conical tightening screw length is critical—too short and the wedge won't fully engage, too long and the screw bottoms out or protrudes.
Screw Length Selection Table:
| Panel A Thickness | Panel B Thickness | Housing Depth | Recommended Screw Length |
| 16mm | 16mm | 12mm | 30-32mm |
| 18mm | 18mm | 14mm | 34-36mm |
| 18mm | 25mm | 14mm | 40-42mm |
| 25mm | 18mm | 18mm | 38-40mm |
| 25mm | 25mm | 18mm | 44-46mm |
| 25mm | 30mm | 20mm | 48-52mm |
| 30mm | 30mm | 22mm | 52-56mm |
Screw Length Formula:
```
Minimum Screw Length = Housing Depth + Panel B Thickness - Counterbore Depth + Engagement Length
Recommended: Add 2-4mm safety margin beyond minimum
```
Common Sizing Errors:
| Error | Consequence | Prevention |
| Screw too short | Incomplete wedge engagement, loose joint | Calculate using formula above |
| Screw too long | Protrudes through panel B, or bottoms out in housing | Verify panel B thickness before selection |
| Wrong thread pitch | Cross-threading, reduced pull-out | Match screw thread to housing specification |
| Incorrect head type | Tool incompatibility, stripped head | Verify hex socket size (typically 4mm or 5mm) |
Connector screws and accessories
Load-Based Size Selection
Matching Housing Size to Load Requirements
The required housing connector size is ultimately determined by the loads the joint must withstand.
Load-Based Sizing Guide:
| Application | Typical Load | Recommended Housing Class | Minimum Panel |
| Display cabinet shelves | <15kg per joint | Small (8-10mm) | 12mm |
| Standard kitchen cabinets | 15-30kg per joint | Standard (12-15mm) | 16mm |
| Heavy kitchen cabinets | 30-50kg per joint | Large (15-18mm) | 18-25mm |
| Wardrobe frames | 25-40kg per joint | Standard-Large (12-18mm) | 16-25mm |
| Commercial shelving | 50-80kg per joint | Large to Heavy-Duty (18-25mm) | 25mm+ |
| Hotel furniture (high use) | 30-60kg per joint | Large (15-20mm) | 22-25mm |
| Industrial cabinetry | 80kg+ per joint | Heavy-Duty (25mm+) | 30mm+ |
| RTA flat-pack furniture | 10-25kg per joint | Standard (12-15mm) | 16-18mm |
Joint Load Distribution
A single furniture joint may contain one or multiple housing connectors. Understanding per-connector versus per-joint loading prevents undersizing.
Load Distribution Guidelines:
| Joint Type | Connectors per Joint | Load Sharing | Per-Connector Load |
| Single connector | 1 | 100% on single connector | = Joint load |
| Two connectors (vertical) | 2 | 50% each if centered | = Joint load ÷ 2 |
| Two connectors (horizontal) | 2 | Uneven—upper takes 60-70% | = Joint load × 0.6-0.7 |
| Three+ connectors | 3+ | Even distribution (±15%) | = Joint load ÷ N |
| Corner joint | 2-3 | Complex—analyze per joint | Varies by geometry |
Recommendation: Always design for the worst-case per-connector load plus a safety factor of at least 2.5x for residential and 3.5x for commercial applications.
Request load calculation support from our engineering team
CNC Bore Requirements
Precision Boring Specifications
Housing connectors require CNC-precision boring for proper installation. Unlike cam locks that tolerate manual drilling tolerance (±0.1-0.15mm), housing connectors demand tighter tolerances for the conical wedge to function correctly.
Bore Specifications by Housing Class:
| Housing Class | Bore Diameter | Tolerance | Bore Depth | Surface Finish |
| Small (8-10mm) | Housing OD + 0.2mm | ±0.05mm | Housing depth + 0.5mm | Smooth, no tear-out |
| Standard (12-15mm) | Housing OD + 0.2mm | ±0.05mm | Housing depth + 0.5mm | Smooth, no tear-out |
| Large (18-20mm) | Housing OD + 0.2mm | ±0.05mm | Housing depth + 1.0mm | Very smooth |
| Heavy-Duty (25mm+) | Housing OD + 0.3mm | ±0.05mm | Housing depth + 1.0mm | Very smooth |
Why CNC Precision Matters:
The conical wedge locking mechanism depends on the housing expanding radially to grip the bore wall. If the bore is:
- Too tight: Housing won't seat properly, risking panel splitting
- Too loose: Insufficient radial expansion → reduced pull-out force
- Out of round: Uneven expansion → stress concentration → potential panel failure
- Too shallow: Housing protrudes → panels won't close flush
Tooling Recommendations:
| Bore Diameter | Recommended Tool | Spindle Speed | Feed Rate |
| 8-10mm | Carbide brad point bit | 12,000-18,000 RPM | 2-4 m/min |
| 12-15mm | Carbide router bit or boring head | 10,000-15,000 RPM | 1.5-3 m/min |
| 18-25mm | CNC boring head with insert tooling | 8,000-12,000 RPM | 1-2 m/min |
| 25mm+ | CNC boring head, roughing + finishing | 6,000-10,000 RPM | 0.8-1.5 m/min |
Material Compatibility
Panel Material Considerations
Different panel materials interact differently with housing connectors. Material density, internal structure, and surface quality all affect connector performance.
Panel Material Compatibility Matrix:
| Panel Material | Density | Housing Holding | Special Considerations |
| MDF (Medium Density Fiberboard) | Medium | Good | Uniform structure, predictable bore quality |
| HDF (High Density Fiberboard) | High | Very Good | Excellent bore definition, high pull-out |
| Particle board | Low-Medium | Fair-Good | Risk of bore wall collapse, use larger housing |
| Plywood (multi-ply) | Medium-High | Good-Very Good | Layer orientation affects expansion grip |
| Solid wood (soft) | Low | Poor-Fair | Grain direction critical, pre-drill carefully |
| Solid wood (hard) | Medium-High | Good | Good holding, but grain variability affects consistency |
| MFC (Melamine Faced Chipboard) | Medium | Fair-Good | Surface chipping risk at bore entry |
Material-Specific Sizing Adjustments:
| Material | Adjustment |
| MDF/HDF | Standard sizing applies; excellent results |
| Particle board | Consider one size up from load-based recommendation |
| Plywood | Standard sizing; ensure bore perpendicular to face |
| Solid wood | Increase housing diameter by 2-3mm; align bore with grain |
| MFC | Use sharp tooling; consider pre-scoring for bore entry |
Connectors optimized for various panel materials
Application-Specific Sizing Examples
Example 1: Standard Kitchen Base Cabinet
Scenario: 18mm MFC panels, base cabinet construction
| Parameter | Selection | Rationale |
| Panel thickness | 18mm (both panels) | Standard kitchen cabinet spec |
| Housing class | Standard (12mm) | Adequate for kitchen loads |
| Housing OD | 12mm | Fits 18mm panel with 6mm remaining |
| Screw length | 34mm | 12mm housing + 18mm panel + 4mm engagement |
| Bore diameter | 12.2mm (±0.05mm) | Standard clearance for 12mm housing |
| Connectors per cabinet | 8 (4 per side) | Even load distribution |
| Estimated per-connector load | 12-18kg | Well within standard housing capacity |
Example 2: Heavy Commercial Display Cabinet
Scenario: 25mm plywood panels, high-load retail display
| Parameter | Selection | Rationale |
| Panel thickness | 25mm (both panels) | Required for heavy retail loads |
| Housing class | Large (18mm) | Needed for 50kg+ per shelf |
| Housing OD | 18mm | Fits 25mm panel with 7mm remaining |
| Screw length | 44mm | 18mm housing + 25mm panel + 1mm tolerance |
| Bore diameter | 18.2mm (±0.05mm) | Tight tolerance for maximum grip |
| Connectors per shelf | 4-6 | Distributed load for glass shelves |
| Safety factor | 3.5x | Commercial public-space requirement |
Example 3: RTA Flat-Pack Bookshelf
Scenario: 16mm particle board, consumer assembly
| Parameter | Selection | Rationale |
| Panel thickness | 16mm particle board | Cost-driven material choice |
| Housing class | Standard (12mm) | Consumer-friendly assembly |
| Housing OD | 12mm | Fits 16mm panel with 4mm remaining |
| Screw length | 30mm | Simple assembly, reduced over-torque risk |
| Bore diameter | 12.2mm (±0.05mm) | Factory CNC pre-bored |
| Connectors per unit | 12-16 | Complete knock-down assembly |
| Special note | Pre-inserted housing | Eliminates consumer boring requirement |
Common Sizing Mistakes and Solutions
Top 5 Sizing Errors
| Mistake | Why It Happens | Consequence | Correct Approach |
| Housing too large for panel | Not accounting for remaining panel thickness | Panel blowout, split | Minimum 3mm remaining behind housing |
| Screw length mismatch | Generic screw selection | Incomplete wedge lock | Calculate per specific panel combination |
| Ignoring material density | One-size-fits-all approach | Poor grip in soft materials | Upsize for low-density panels |
| Bore tolerance too loose | Manual drilling instead of CNC | Reduced radial expansion → weak joint | Use CNC boring with ±0.05mm tolerance |
| Undersizing for load | Only considering panel thickness | Joint failure under load | Size by load requirement first, then verify panel compatibility |
Technical sizing consultation available
Sizing Decision Flowchart
When selecting a housing connector size, follow this decision sequence:
Conclusion
Correct housing connector sizing is the foundation of reliable cabinet construction. Unlike simpler connector types that tolerate sizing variation, housing connectors require precise matching of housing diameter, screw length, panel thickness, and bore specification. Getting these parameters right unlocks the full potential of the conical wedge locking mechanism: exceptional pull-out resistance, vibration stability, and long-term durability.
Key takeaways:
At Shaxi Hardware, we manufacture housing connectors across the full size range—from 8mm small housings for thin decorative panels to 25mm+ heavy-duty housings for industrial cabinetry. Our engineering team provides detailed dimensional drawings, CNC tooling recommendations, and application-specific sizing support.
For custom housing connector specifications, dimensional drawings, or technical sizing consultation, contact our engineering team directly.
Request housing connector sizing consultation
Additional Resources
- [Link to: /collections/connecting-fittings – Connecting Fittings Product Line]
- [Link to: /collections/furniture-connecting-fittings – Furniture Connecting Fittings]
- [Link to: /collections/connecting-fittings-solutions – Connector Solutions Overview]
- [Link to: /collections/shelf-support – Shelf Support Range]
- [Link to: /pages/contact – Engineering Support & Custom Specifications]
- [Link to: /pages/about-us – About Shaxi Hardware]
About Shaxi Hardware
With over 15 years of experience manufacturing furniture hardware, Shaxi Hardware serves brands and manufacturers across 40+ countries. Our ISO 9001 certified production facility specializes in housing connectors, furniture connectors, shelf supports, plinth feet, and adjustable connecting levellers. All products undergo rigorous quality control testing for dimensional accuracy, load capacity, and material integrity. We provide comprehensive technical documentation including dimensional drawings, CNC tooling guides, and application-specific sizing recommendations.
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