Lock cylinder buying guide

Lock cylinder buying guide

Sebastian, self-taught DIY-er, Exeter

Guide written by:

Sebastian, self-taught DIY-er, Exeter

"Oops! The key broke off in the lock on the front door" or "Help! My key won't turn in the lock!" Lock cylinders are a real minefield... half-cylinders, round, button, high security, 30x40... Stop! Let's get back to basics.

Important features

  • Classic cylinder
  • Half-cylinder
  • Disengageable
  • Button
  • Size
  • Type of protection
  • Key type
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A quick overview of the various types of cylinders...

The most common type of lock cylinder (also called a barrel), is the European cylinder. It's always the same general shape, but it comes in a range of different materials, sizes, and brands and importantly with different types of keys and locking mechanisms.

A European cylinder can be either classic, disengageable, button or half-cylinder.

It may offer safety features such as anti-pick, anti-drill, anti-smash and anti-copy. Certain brands also produce completely round lock cylinders, distinct from the European type and much less common.

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Types of keys

How to choose the length of your cylinder?

The first and most important characteristic when replacing a lock cylinder is the length. The cylinder consists of a keyhole on each side and a bit in the middle activated by the key.

The length is measured from the centre of the bit up to the keyhole. The great majority of cylinders are 60mm in total length, and are known as 30-30 because it's 30mm between the bit and the keyhole on either side. However, variations are possible, including:

  • 30-40;

  • 40-40;

  • 40-50 etc.

The reference points are always the centre of the bit and the keyhole. Knowing these values alone will allow you to change your cylinder without going wrong!

The bit, when the key isn't in the cylinder, is usually at7 o’clock (clock face position) when viewed from the front. It can also be at 3, 9 or 12 o'clock on other more specific locks. Some cylinders have an adjustable bit.

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Keys, cylinders... what level of security do I need?

Depending on the cylinder, your key will have a range of notches and recesses, bumps and hollows. The profile of the key, sometimes cross- or star-shaped but typically flat, can becut on one or both sides. It's a combination of size and profile that carries the "code" to activate the pins inside the cylinder and allow you to operate the lock. The correct profile lets the key enter the cylinder, the correct series of notches lets you turn it and lock up!

The more pins, the harder the lock is to pick - the number can be anywhere from 5 to 36.

You can increase the complexity of your cylinder when replacing it to increase the security level of the lock. The shape of the key is a clue to the complexity of the cylinder:

  • A flat key notched on one side is the standard, found on keychains the world over;

  • A flat key notched on both sides indicates a higher security level since the cylinder has more pins;

  • Paracentric keys are similar to the previous two types, except they're notched on the cutting edges for better protection against picking;

  • Reversible keys, as the name suggests, can be inserted in either direction;

  • Pump keys are star-shaped in form and offer a high level of security.

The number of keys sold with the cylinder varies - often 3 or even 5 for more sophisticated models. Depending on the type, keys can be copied more or less easily. Flat keys can be reproduced in any small key cutter's, paracentric and reversible types are offered in some more professional shops, and pump keys can only be cut by a select few including the original manufacturers. Some are "uncopiable" or at least require you to provide a card supplied with the cylinder to get them reproduced.

Attention, keys guaranteed for life can only be reproduced in the factory: think of the delay!

Is it just the complexity of the mechanism that makes a cylinder secure?

No, that's not all! A cylinder can be drilled to blow the pins or broken with a hammer from the outside. For this reason, you can get locks with a steel pellet just below the keyhole; a washer is also incorporated to avoid drilling - so the drill spins on empty! It can also be made of a highly durable alloy to withstand breaking by force... On this point, it's important to make sure the cylinder doesn't protrude out from the door. It must be flush to avoid giving purchase to pulling tools.

So, a cylinder can therefore be protected against:

  • Tearing - using pliers;

  • Percussion-based breakage - hammers etc;

  • Drilling;

  • Picking - with a bent wire;

  • Key copying

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Half-cylinder, disengageable cylinder, button... What's the deal?

Allow us to explain!

  • Conventional cylinder: there's a keyhole on both sides but can only be operated with one key inserted at a time.

  • Half-cylinder: specifically designed for garage doors, these cylinders only have a keyhole on one side, giving them the format 30-10mm.

  • Disengageable: a key inserted on one side doesn't prevent the lock being opened from the other, super convenient if there are lots of you in the house. (Although conventional cylinders, since they can't be turned with a key inside, are useful if you don't want anyone to come in - even with a key!)

  • Button: a button is attached to the cylinder, removing the need for a key from the inside.

Pay particular attention to the small locks on bay windows and gates: since the bit is smaller, if you can't find the model of your choice, you might have to take matters into your own hands: file the bit down so it fits easily inside the lock!

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What different types of lock mechanisms are there?

From the simplest to the most sophisticated mechanism, these are available in all sizes and formats of cylinder!

  • Pins: the most common mechanism; the more pins, the higher the security level - most cylinders have six pins. Choose a cylinder with an anti-pick security feature. Nickel-plated mechanisms (highly durable alloy) are safer. Depending on the arrangement of the pins, it may be difficult to copy the key.

  • Balls: this type of mechanism is impervious to drilling.

  • Discs: if you're just a rookie-level user, there's no need to go out of your way for this fancy mechanism offering a very high level of security.

  • Pump: with improved durability and resistance to picking, this type of mechanism is also more expensive than the ball or pin systems.

Can you have one key for several cylinders?

Oh yes!...

But you'd better keep track of it!

You just need interchangeable cylinders. They all share one key, lightening your keychain considerably! Of course, they can still have a range of mechanisms.

Final advice before we lock up for the night?

Replacing a cylinder is quite simple, it's held in place by a screw, accessible from the edge of the door, which passes through the lock. You unscrew it (after removing the key of course!), then you just have to pull the cylinder out.

A lock cylinder is only as good as the door it protects. No need to buy a high-security lock if your door's made of cardboard and can be knocked down by a feather! The strikeplate and lock housing are equally important, and must be robust and securely mounted.

To summarize, choose your cylinder according to:

  • The model already in place, if it's a replacement;

  • Size;

  • Type ;

  • Security features;

  • Key type.

Don't hesitate to use a lubricant product if your locks are sticking!

To find out more about locks and related topics, follow our editors' advice and check out their other guides:

How to choose your hammer?How to choose your drill bits?How to choose your front door?How to choose your drill?How to choose your screws?How to choose your lubricants, grease and oil?How to choose your garage door?How to choose your gate operator?

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Guide written by:

Sebastian, self-taught DIY-er, Exeter

Sebastian, self-taught DIY-er, Exeter

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