A key broke off in the lock: what to do now

The first sixty seconds

1. Stop touching it. Everything that goes wrong from here happens in the next few minutes.
2. Do not put the other half back in. It cannot push the broken piece out, and it will push it deeper and jam it against the pins.
3. Do not turn the lock. If the plug is rotated away from its resting position, the piece is trapped by the pin chambers and cannot come out at all. If it has already turned, leave it exactly where it is and say so when you call.
4. Look at how much is showing. Sticking out of the keyway is a very different situation from flush or buried, and it is the first thing anyone will ask you.

If a piece is sticking out

This is the one version you can often solve yourself.

• Use fine needle-nose pliers or firm tweezers — something that grips the flat of the blade, not something that crushes it.
• Pull straight out, along the line the key went in. No twisting, no rocking, no levering against the face of the lock.
• A very light spray of a dry lubricant made for locks — graphite or a PTFE type — can help it slide. Give it a moment to work in.
• If it does not move on a firm steady pull, stop and call somebody. Force at this point breaks the fragment again deeper inside.

What not to do, and what it does to the lock

• Superglue. The most expensive idea on this page. Glue wicks straight into the pin chambers, sets the fragment to the plug and the plug to the housing, and turns a five-minute extraction into a cylinder that has to come off the door. A glued key also has no strength across its length and snaps again immediately.
• Household oil or all-purpose penetrating spray. Wet lubricants attract dust and turn the inside of a cylinder into grinding paste. The lock gets stiffer over the following weeks — which is how it broke a key in the first place.
• Pushing with a thin screwdriver, a paperclip or another key. Every one of these drives the fragment deeper. Deeper is worse.
• Hacksaw blades levered in by hand. Professionals do use a saw-toothed extractor, but the amateur version snaps the blade off inside the keyway and now there are two things stuck in your lock.
• Drilling it out yourself. You will destroy the cylinder, and often the housing around it, to remove a piece of brass that would have come out with the right hook.
• Forcing the door instead. A snapped key does not mean you have to get in through the frame — see locked out of your house at night before anybody kicks anything.

When to call somebody

• The fragment is flush with the face of the lock or completely inside it.
• The plug has been turned since the key broke.
• The key broke in a car ignition, a mortise lock, a storefront lock or a high security cylinder.
• You are locked out and the broken key was the only one.
• You have already tried something and it did not come out.
• The key snapped in a padlock or a storage unit you need access to today.

What a locksmith actually does

1. Confirms the property or vehicle is yours. Photo identification and something that connects you to it, before any tool comes out.
2. Returns the plug to the resting position. The fragment can only leave the keyway when the plug is lined up with the housing, so this comes first if the lock was turned.
3. Uses a key extractor. These are thin steel tools with a hook or a spiral edge that slide alongside the blade in the keyway, catch a cut, and draw the piece back out. Two are often used together to keep the fragment straight. It is fiddly and it is quick.
4. Cuts you a working key. From the surviving half where enough of it remains, or by decoding the cylinder and cutting to that. You leave with a key, not just a cleared lock.
5. Looks at why it happened. A cylinder full of grit, badly worn pins, a misaligned latch loading the key on every turn — those get fixed or the next key breaks too. That is lock repair work.

Stopping the next one

• Treat stiffness as a warning. A lock that needs a wiggle, a lift or a shove is a lock that is going to snap something. It is a short service job before it breaks and a bigger one afterwards.
• Retire worn keys. Copies of copies get progressively vaguer and put more strain on both key and lock. Where the code is available, a key cut fresh to the original specification is stronger than a copy of a copy.
• Use dry lubricant, once or twice a year. Not oil, not general-purpose spray.
• Stop using keys as tools. Prying, scraping and opening packaging is how a blade develops the microscopic bend that fails six months later.
• Fix the door, not just the lock. If you have to pull the door towards you to turn the key, the frame is loading the bolt every single time. See when the key turns but the door will not open.