A standard euro cylinder is a barrel that fits into the lock mechanism. The 80mm length is a combination of two measurements, one from the center of the fixing screw to the outside of the door (the external measurement) and one to the inside (the internal measurement).

• Total Length: 80mm

• Split Measurement: The cylinder could be a symmetrical “40/40” split or an asymmetrical split like “35/45,” “30/50,” or even “45/35.” The first number usually corresponds to the external measurement.

Why the split matters: The correct split measurement is essential for proper security and function. If the cylinder protrudes too far on the outside, it becomes a major vulnerability to a common burglary method called “lock snapping.”

Key Security Features

Given that the cylinder is often the weakest point in a UPVC door’s security, an 80mm cylinder should be chosen with a focus on its resistance to common attacks. High-security cylinders are designed to combat:

• Lock Snapping: This is a technique where a burglar applies brute force to snap the cylinder in half. Anti-snap cylinders are designed with a sacrificial front section that will break away while leaving the core of the lock intact, preventing the burglar from gaining entry.

• Drilling: An anti-drill cylinder has hardened steel pins and plates that make it extremely difficult for a burglar to drill through the lock.

• Picking: This is the traditional lock manipulation method. An anti-pick cylinder uses a more complex pin system to resist picking tools.

• Bumping: This involves a specially cut key that, when “bumped” with a blunt object, can open the lock. An anti-bump cylinder has a unique design to prevent this.

Types of 80mm Casement Door Cylinders

The primary types of euro cylinders are defined by their operation:

• Double Cylinder (Key-to-Key): This is the most secure option for an external door, as it requires a key to operate from both the inside and the outside. This is a good choice for a door with a glass pane, as a burglar cannot simply break the glass and turn a knob from the inside.

• Thumbturn Cylinder: This type has a key on the outside and a thumbturn knob on the inside. It allows for quick and easy locking/unlocking from the inside without a key, which can be useful for fire safety or convenience. However, it can make the door vulnerable if a burglar can reach the thumbturn by breaking a nearby window.