Introduction
The euro cylinder is one of the most important components of your door's locking system. It's the part you insert your key into and, although relatively small, it plays a vital role in both the security of your home and the everyday operation of your door.
Whether you're replacing a worn lock, upgrading your home's security or choosing a cylinder for a new door, understanding the different sizes, types and security ratings can help you make the right choice.
What Is a Euro Cylinder?
A euro cylinder is the removable lock fitted to most:
- uPVC doors
- Composite doors
- French doors
- Patio doors
- Some timber doors
The cylinder sits inside the gearbox of the multipoint locking mechanism or lock case with escutcheons.
When you turn the key, a cam in the centre of the cylinder rotates, allowing the gearbox to operate the hooks, rollers, deadbolts and latch that secure the door.
Without a correctly functioning cylinder, the locking system cannot operate properly.
How Does a Euro Cylinder Work?
Although the cylinder appears simple from the outside, it contains a series of precision pins and springs.
When the correct key is inserted:
- The pins align.
- The plug inside the cylinder rotates.
- The cam turns.
- The gearbox is activated.
- The multipoint locking mechanism locks or unlocks the door.
If the wrong key is used, the pins remain misaligned and the cylinder cannot rotate.
How Are Euro Cylinders Measured?
Euro cylinders are measured from the centre of the fixing screw to each end of the cylinder.
Typical sizes include:
- 35/35mm (70mm overall)
- 40/40mm (80mm overall)
- 45/45mm (90mm overall)
- 35/45mm (80mm overall)
- 40/50mm (90mm overall)
The internal and external measurements are often different, which is why many cylinders are asymmetrical.
Accurate measurement is essential before ordering a replacement.
Why Correct Sizing Matters
Choosing the correct size isn't simply about making the cylinder fit.
If it's too long it may:
- Protrude beyond the handles.
- Become easier to grip.
- Increase vulnerability to attack.
- Look untidy.
If it's too short it may:
- Sit too far inside the handles.
- Make inserting the key awkward.
- Prevent correct operation.
- Cause fitting problems.
Ideally, the cylinder should sit flush with the handles or project by no more than around 2–3mm.
Types of Euro Cylinder
Several styles are available depending on the application.
Double Cylinder
Operated by a key from both sides.
Commonly fitted to front and rear doors.
Thumbturn Cylinder
Uses a key externally and a thumbturn internally.
Allows the door to be unlocked quickly from inside without using a key.
Half Cylinder
Used on:
- Garage personnel doors
- Meter cupboards
- Commercial applications
Only one side accepts a key.
Keyed Alike Cylinders
Allow multiple locks to operate using the same key.
Popular for homeowners wanting one key for the front door, back door and garage.
Understanding Security Ratings
Not every euro cylinder provides the same level of protection.
Standard Cylinders
Many older doors still use standard cylinders.
Although perfectly functional, they often provide limited protection against modern burglary techniques.
TS007 1 Star Cylinders
A TS007 1 Star cylinder provides improved protection against lock snapping.
To achieve the highest TS007 security rating, it should be used alongside a TS007 2 Star security handle.
TS007 3 Star Cylinders
A TS007 3 Star cylinder achieves the highest TS007 rating without relying on a security handle.
These cylinders are designed to resist:
- Lock snapping
- Drilling
- Picking
- Bumping
For many homeowners, a quality 3 Star cylinder offers the simplest security upgrade.
Which Euro Cylinder Should You Choose?
The right choice depends on your priorities.
A standard cylinder may be suitable if you're replacing a worn lock like-for-like.
A TS007 1 Star cylinder combined with a TS007 2 Star handle offers excellent protection.
A TS007 3 Star cylinder is ideal if you want high-level security without replacing your existing handles.
Whichever option you choose, correct sizing is just as important as the security rating.
Related guides:
Signs Your Cylinder Needs Replacing
Your euro cylinder may be reaching the end of its life if you notice:
- The key becoming difficult to turn.
- The key sticking.
- Difficulty removing the key.
- Rough or inconsistent operation.
- A snapped key.
- Internal wear.
- Lost or stolen keys.
- You've recently moved home.
- You want to improve your home's security.
Replacing the cylinder is often one of the quickest and most affordable security upgrades available.
It Might Not Be the Cylinder
A stiff key doesn't always mean the cylinder has failed.
Many similar symptoms are actually caused by:
- A dropped door.
- Poor alignment.
- A worn gearbox.
- A failing multipoint locking mechanism.
- Excessive pressure on the locking points.
Replacing a perfectly good cylinder won't solve these problems.
Correct diagnosis always comes before replacing parts.
Quality Makes a Difference
Euro cylinders vary considerably in quality.
A well-manufactured cylinder generally provides:
- Smoother operation.
- Better reliability.
- Longer service life.
- Greater resistance to attack.
- Improved key control.
- Better overall security.
Combined with a properly aligned door and quality locking mechanism, a good cylinder can provide many years of dependable service.
Don't Forget the Rest of the Door
Even the highest-security cylinder can't compensate for problems elsewhere.
For maximum security your door should also have:
- A correctly operating multipoint locking mechanism.
- Good door alignment.
- Secure, well-fitted handles.
- Properly adjusted keeps.
- Hinges in good condition.
Every component works together to keep your property secure.
Conclusion
The euro cylinder may be one of the smallest parts of your door, but it has one of the biggest influences on both security and everyday reliability. Choosing the correct size, selecting an appropriate security rating and fitting a quality cylinder can greatly improve how smoothly your door operates while providing increased protection against common methods of attack.
Whether you're replacing a worn cylinder, upgrading to a TS007 high-security model or simply trying to identify the correct size, taking the time to choose the right product will help keep your door secure and operating reliably for many years.
