Key Clamp Fittings: Complete Sizing & Selection Guide
Last updated: March 2026
Quick Answer
Key clamp fittings are galvanised tube connectors for building handrails, barriers, and structures. Match the fitting size to your tube outer diameter: Size B (34mm) is most common for handrails. All fittings are BS EN 1562 compliant for structural use.
Key Clamp Size Chart
| Size Code | Tube OD | Nominal Size | Common Uses |
|---|---|---|---|
| Size A | 26.9mm | 27mm / ¾" | Clothing rails, light structures |
| Size B | 33.7mm | 34mm / 1" | Handrails, barriers, most applications |
| Size C | 42.4mm | 42mm / 1¼" | Heavy-duty handrails, fencing |
| Size D | 48.3mm | 48mm / 1½" | Structural frames, scaffolding |
| Size E | 60.3mm | 60mm / 2" | Heavy structural, sign posts |
Which Size Do I Need?
For standard handrails: Size B (34mm) is the industry standard. It meets building regulations, is comfortable to grip, and offers the widest fitting choice.
For heavy-duty applications: Size C (42mm) or Size D (48mm) provides greater strength for industrial barriers, mezzanine rails, and high-traffic areas.
For decorative/light use: Size A (27mm) suits clothing rails, display stands, and non-structural applications.
How Key Clamp Works
Key clamp fittings grip the outside of standard steel tube using a grub screw mechanism. No welding, threading, or special tools required - just an Allen key. Fittings can be repositioned, making key clamp ideal for:
- Handrails and balustrades
- Safety barriers and guardrails
- Mezzanine flooring edges
- Pedestrian walkways
- Bike racks and shelters
- Retail displays and shopfitting
Frequently Asked Questions
Is key clamp strong enough for handrails?
Yes. Key clamp fittings manufactured to BS EN 1562 are rated for structural handrail applications. Size B (34mm) systems are commonly used in commercial buildings, schools, and public spaces.
What tube do I use with key clamp?
Standard steel tube (CHS - Circular Hollow Section) to BS EN 10255 or BS EN 10219. The tube must match the fitting size exactly. We recommend galvanised tube for outdoor use.
Can key clamp be used outdoors?
Yes. Our fittings are hot-dip galvanised (minimum 40μm coating) for corrosion resistance. Combined with galvanised tube, key clamp systems last 25+ years outdoors with minimal maintenance.
How do I calculate handrail materials?
Measure the total run in metres, add 10% for cuts. Count corners, ends, and mid-rail joints. Each junction needs a fitting (elbow, tee, or flange). We offer free take-off service - send us your drawings.
Browse key clamp fittings: Size B (34mm) | Size C (42mm) | Size D (48mm)