A broken key in the lock: what to do and what to avoid

A key breaks when the metal is asked to do more than it can. Most keys are made from brass or nickel silver, which are soft enough to cut easily and strong enough for daily use, but not strong enough to resist a hard twist when a lock is jammed. The weak point is usually where the blade meets the head, or at a deep cut along the blade, where the metal is thinnest.

When the break happens, one of two things is true. Either a piece of the blade is sticking out of the keyway and you can still see it, or the whole blade has snapped off flush and sits inside the cylinder. Either way, the pins in the lock may be holding the piece in place, and the cylinder is blocked for any other key.

Take a breath. A broken key is one of the most common calls any locksmith gets, and it is rarely a disaster. The lock is almost always fine, and the broken piece can be removed with the right tools. What matters now is not making it harder.

It also helps to know what is going on inside. A pin tumbler cylinder holds rows of pins that must all be lifted to one exact height. A broken piece still touches several of those pins, so the cylinder feels blocked even though nothing inside is truly jammed. Once the piece is drawn out cleanly, the pins fall back to rest and the lock usually behaves as if nothing happened.

Wear is the usual reason. A key that has been used thousands of times develops tiny cracks along the cuts, a kind of metal fatigue. One day a little extra twist is all it takes. Keys that have been copied many times can be thinner or cut more deeply than the original, which makes them more fragile.

A lock that is already stiff adds strain. Cold weather, dust, a misaligned door or a worn cylinder can all make the key harder to turn. A person who leans harder to compensate puts extra stress on the blade. Keys also break when used as tools, such as for opening a package, tightening a screw or prying something loose.

A key left in a lock and then bumped, or a key stuck in a door that is slammed, can snap as well. The pattern repeats: a little wear, a little resistance and a little force. If your key has a visible crack, a bend or a worn shoulder, replace it before it breaks, rather than after.

Seasons play a part in the North State. Cold mornings in the mountain towns make metal brittle and lock oil stiff, and a key that turned easily in August may resist in January. In the valley, summer heat expands doors and frames, tightening the fit of the bolt in its strike. Both swings put extra load on the key, and a worn one can give up at exactly the wrong moment.

First, stop turning and stop pulling. Do not try to turn the lock further with the broken piece. Look at the key. If part of the blade sticks out far enough that you can see the end clearly, you may be able to grasp it. If nothing is visible, leave it alone.

Second, take stock of your safety. If you are locked out of a car with a child or pet inside, or out of a home with someone who needs help, contact emergency services first. Otherwise, move to a safe spot out of the weather, and take a photo of the lock with your phone so you can describe it.

Third, hold on to every piece. The part in your hand has information, such as the key code stamped on the bow or the cut pattern on the blade. A locksmith can use the broken piece to cut a new key. If the piece is still in the lock, remember what the head looks like, and whether it is a standard key or has a chip in the head.

If you are outside in bad weather, think first about your comfort and safety. Get your coat on, get out of the wind, and make sure you have a way to stay warm while help is arranged. A broken key is a problem for the lock, but you are the one who matters. Once you are settled, you can think clearly about the next step.

• Stop turning, stop pulling and stop pushing.
• Keep every piece of the key, including the head.
• Photograph the lock and the key for reference.
• Call emergency services first if a person or animal is in danger.
• Avoid putting anything else into the keyway.

The internet is full of tricks involving superglue, tape, a paperclip or a bent hairpin. Please avoid all of them. Glue can run into the cylinder and weld the pins in place, turning a simple extraction into a full lock replacement. A paperclip or hairpin can push the broken piece deeper, or bend the thin springs behind the pins.

Pliers are a risk too. If a piece sticks out slightly, clamping it with pliers and pulling can snap it off flush, or tear the pins as it comes out. Needle nose pliers have their place in careful hands, but the grip must be right and the piece must be loose. If you feel resistance, stop.

Do not hammer, drill or spray the lock with heavy oil. Hammering shocks the pins and can damage the door. Drilling destroys the cylinder, usually forcing a full replacement. Thick lubricants can gum up the lock and make extraction harder. A light touch or no touch is better than a heavy one.

One more habit to avoid is trying a spare key in the lock while the broken piece is still inside. A second key pushing in alongside a broken piece can jam both together or push the piece back further. Wait until the keyway is clear. A spare is for after the extraction, not before it.

If a quarter inch or so of the blade is exposed, a gentle approach may work. Check that the lock is in the position where the key goes in and comes out, usually with the cylinder in the neutral, upright position. If the key broke while turning, the cylinder may be rotated partway, which holds the piece firmly.

With clean, dry fingers or a pair of fine tweezers, take a firm grip on the exposed end and pull straight out along the line of the keyway. Do not twist or rock. Give it a few careful tries. If the piece moves, great. If it does not, stop at once. Extra pulling can snap it off flush and take away your last handle on it.

Many people want to use a small blade or the edge of a tool to hook the key. We understand the impulse, but the pins and springs inside are delicate, and a hook can push them into a worse position. If the exposed piece does not come out easily, leave it for a professional.

If you do manage to pull the piece out, resist the urge to test the lock at once with the same key. A key that has just broken is likely to break again, because the crack that failed once may be present elsewhere on the blade. Use a fresh, undamaged key, ideally one cut from the original, and see whether the lock turns smoothly.

If the broken piece sits flush with the face of the lock, or deeper, there is nothing to grip. This is where professional extractors come in. They are thin, hardened tools with tiny hooks or serrations, designed to catch the cut edge of the key and draw it out without disturbing the pins.

A locksmith will usually begin by clearing the keyway of any debris and inspecting the position of the piece with light and magnification. The tool is slid in along the keyway, hooked onto the broken piece, and pulled out in a straight line. Often it takes several careful tries. Some pieces come out in one go, and others need patience.

If extraction is not possible without damage, there are other options. The cylinder can be removed from the door and opened on the bench, where the pins and the piece can be handled safely. This is a delicate job that is much easier with the cylinder out of the door. Afterwards, the cylinder is cleaned, tested and refitted, or replaced if it is damaged.

Owners sometimes wonder whether the lock must be replaced after an extraction. Most of the time it does not. The tools used are thin and gentle, and the pins are designed to take thousands of insertions. If the cylinder is scored or a pin is bent, we will say so plainly and explain whether a repair or a replacement makes the most sense for that door.

Once the broken piece is removed, the lock is tested. We check that a clean key turns smoothly, that the pins move freely and that no part of the cylinder is bent or scored. We also ask why the key broke. If the lock was stiff, a good cleaning and the right lubricant may be all it needs.

Then comes the new key. A broken key can be duplicated from the two halves if they fit together, or cut by code, or made from a spare. If you have no spare, a locksmith can cut a new key from the lock itself. We encourage you to make a spare at the same time, and to store it safely, using the ideas in storing spare keys safely.

If the broken key was a copy, consider going back to the original code. Copies of copies have small errors that add up and place extra strain on the lock. Our notes on why duplicate keys sometimes fail explain this.

Many people ask how a new key is made when the original is in two pieces. If the pieces can be matched, the cut pattern can be traced. If they cannot, the pin heights inside the lock reveal the cut pattern, and a key can be produced from that information. In every case, the aim is a clean, accurate key made without wear from the older ones, so the lock gets a fresh start.

Vehicle keys add complications. Many modern car keys have a plastic head with a chip, or a fold out blade, and the break may happen at the hinge. An ignition with a broken piece inside is more delicate still, since the cylinder is part of the steering column. An automotive locksmith can often extract the piece without removing the column, and can then cut and program a new key.

Padlocks, mailbox locks and cabinet locks are smaller, and the keys are more fragile. The principles are the same: do not force, do not glue, keep the pieces. For padlocks used on gates, trailers and storage, a broken piece in a cold lock is common in winter, and thawing may loosen it before you try anything else.

If you carry keys while hiking, fishing or boating, they take extra abuse. Salt, sand and sudden knocks can weaken a key. Our guide on carrying keys while hiking, fishing and boating has ideas for protecting them.

Car keys carry a further cost when they break. If the chip is in the head and the head is intact, it may be possible to transfer the chip to a new blade. If the chip is damaged, a new transponder key must be programmed to the vehicle. Our notes on transponder keys explained go through how that works.

The strongest prevention is a healthy lock and a healthy key. Keep the keyway clean, use the right lubricant, and replace keys that show cracks, bends or heavy wear. If a lock has started to feel stiff, deal with it before it becomes a snapped key. Our article on keys that will not turn lists what to check.

Choose a sensible key ring. Heavy bunches of keys hanging from a lock put sideways strain on the cylinder as the key turns. Remove the lock from the weight of the ring by holding the key itself, not the whole bunch. Avoid using the key as a screwdriver or a scraper.

Make spares before you need them. A spare cut from the original is a small step that turns a broken key from a crisis into an annoyance. Keep one at home in a safe place, and consider leaving one with a trusted person. Preparation is the quiet backbone of good lock care.

Think too about how you carry and use keys on a daily basis. Do not leave a key sitting in a lock overnight, since a bump or a gust of wind against the door can stress it. Take the key out of the lock before you open the door, and take it out of the ignition before you leave the vehicle. A few small habits protect a key far better than most people expect.

When you call or write, describe the lock, the part of the key that broke, and what you have done so far. Tell us if the lock is on a car, a house, a business or a padlock. If it is a vehicle, say the make and year, since that affects the key type. Photos help.

The phone line is coming soon, so the way to reach our team right now is the request form. Include where you are and what happened. If it is urgent or someone is in danger, contact emergency services directly.

We handle this work as part of lock repair, and for vehicles under automotive locksmith service. If you are locked out as well, see house lockout or car lockout.