A key is a tiny precision part
A house key looks like a simple piece of metal, but it is a precision part. The ridges and valleys cut along its blade are measured in fractions of a millimeter. Each cut must lift a pin inside the lock to exactly the right height. If any cut is a hair too deep or too shallow, the pin sits wrong and the lock will not turn smoothly, or will not turn at all.
Because the tolerances are so small, even slight wear matters. Every time you insert and remove a key, the metal rubs against the pins inside the lock. Over months and years, the high points on the key wear down and the pins wear as well. Dirt, grit and moisture speed it along. The result is a key that no longer lifts the pins accurately.
Brass, the metal used for most house keys, is relatively soft. That is a good thing for the lock, since the key wears instead of the cylinder, but it means keys do not last forever. A key you have used daily for ten years is a worn key, whether or not it looks it. The same is true for a key you have used less often but kept in a pocket with coins and other keys.
The good news is that a worn key is the easiest problem to fix. The less good news is that people often ignore the early signs until the key breaks. Our page on a broken key in the lock describes how that goes and why it is worth avoiding.
Copies of copies and why they degrade
Most keys in a household are not originals. They are copies, and many are copies of copies. Each time a key is duplicated, the new key is cut by tracing or measuring the old one. Small errors creep in. A key cut from a worn original inherits the wear, and then adds a little error of its own. By the time you are using a third- or fourth-generation copy, the cuts may be noticeably off.
This is why a new key from a hardware store sometimes does not work well at first, or does not work at all. The machine may have been poorly adjusted, the blank may have been the wrong type, or the original may have been too worn to copy cleanly. A copy that is rough around the edges, with burrs left from cutting, can also catch inside the lock and wear it faster.
The best practice is to keep a good original, or a precisely cut key from a reliable source, and use it only to make copies. Avoid making copies from a copy that is already rough. If you have a key that has always been a little stiff, replace it with a clean one rather than continuing to use it. Our page on key cutting and copy quality explains what a good copy looks like and what to check.
If you have a spare key that has never worked well, test it now, on a calm day with the door open, not when you are locked out and relying on it.
- Each generation of copy adds small errors
- Burrs left from cutting can catch inside the lock
- A worn original makes a worn copy
- Test spare keys with the door open, before you need them
Signs the key is the problem
There are a few clues that the key, rather than the lock, is at fault. The first is that only one key misbehaves. If you have two or three keys to the same lock and one of them sticks while the others turn smoothly, the sticky one is almost certainly worn or poorly cut. The second is that the key looks different. Compare it to a newer key side by side. If the ridges are rounded, the tips are shortened or the edges are shiny and worn, the key is tired.
A third clue is that the problem began after a copy was made. If a key from a particular copy has never worked well, the copy is the issue. A fourth is a bent or twisted key. A key that has been used as a lever, bent in a pocket or stepped on may have a slight bow that makes it hard to turn. Trying to straighten it often makes things worse, since brass can crack when bent back.
A fifth is visible damage: a crack at the bow, a chipped tip, a worn stamping. These are signs the key may break soon. If a key shows any of these, retire it. Use a good copy and keep the old one only if it is an original that can be used as a pattern, or discard it.
None of these signs is a reason to panic. They are simply a reason to replace the key now, while it is still a convenience and not an emergency.
Signs the lock is the problem
If all your keys, including new ones, feel rough in the same lock, the lock is likely the cause. A cylinder that has worn, collected grit or corroded will make every key feel gritty. Other signs include a key that goes in but will not turn without jiggling, a key that turns only when you pull the door toward you or lift it, a plug that feels sluggish or springy, or a lock that works in the morning and not in the evening.
Humidity and salt air are common culprits in South Florida. Moisture can cause pins to stick, springs to weaken and metal to corrode. Warm weather expands brass and steel slightly, and a lock that feels fine in winter may be stiff in summer. Dirt and old lubricant can combine into a sticky film that makes the pins sluggish.
Another possibility is that the cylinder has been damaged by earlier use, for example by a forced attempt, a key that was broken off and extracted or a lubricant that has gummed up. A technician can inspect the cylinder and tell you whether cleaning, rekeying, repinning or replacement is appropriate.
Our pages on a lock that will not turn and salt air and lock corrosion in South Florida go into these causes in more detail.
Signs the door is the problem
Sometimes neither the key nor the lock is at fault. The door itself has shifted. In humid climates, doors swell and frames move. A hinge may sag, causing the door to drop slightly and the deadbolt or latch to land off center in the strike plate. You turn the key and nothing happens, or the key turns but the bolt will not extend, because the bolt is pushing against the frame.
A telltale sign is that the lock works smoothly when the door is open and stiffens when the door is closed. Another is that lifting or pushing on the door while turning the key makes a difference. A third is a visible gap that is uneven along the edge of the door, wider at the top and narrower at the bottom, or the reverse.
In these cases, replacing the key or the cylinder will not fix the problem. The solution may be adjusting the hinges, repositioning the strike plate or correcting the frame. A technician can assess the alignment as part of a lock visit. Read hinges and door sag in Florida and door frame and jamb problems in humid climates for more.
If you suspect the door is the problem, avoid forcing the key. Forcing against a misaligned bolt can bend the key or damage the lock.
What not to do when a key sticks
When a key will not turn, the natural instinct is to force it. Resist that. A worn or bent key under force can snap, leaving a piece inside the lock. That turns a small problem into a larger one. The same applies to using pliers, a hammer or a pry bar. These can damage the key, the cylinder and the door.
Avoid spraying heavy oils into the lock. Household lubricants can attract dust and gum up over time, making the problem worse. If you want to lubricate, use a product made for locks and apply it sparingly. Our page on lock lubricant and maintenance basics describes what to use and what to avoid.
Do not try to file or reshape a key yourself. Small changes to the cuts can ruin a key and may damage the pins inside the lock. If a key is rough, have a new one cut.
If a key is stuck and will not come out, do not yank on it. Stop, and call. See a key stuck in the lock for what is likely happening and what a technician checks. A calm approach saves the key, the lock and your day.
Getting a good replacement key
A good replacement starts with a good pattern. If you have an original key that is not badly worn, use it. If every key you have is a copy, choose the one that works best and that looks least worn. A locksmith can often cut a key by matching the lock itself, which avoids copying copies, though that may require an on-site visit.
Quality of the blank matters too. A blank that is the right brand and profile for the lock will fit better than a generic one. Some keyways are common and some are less common, such as restricted keyways that require authorization to duplicate. Our page on restricted keyways and key control explains the difference.
After a new key is cut, test it with the door open, and again with the door closed. It should slide in smoothly, turn without force and withdraw cleanly. If it does not, bring it back. A good copy should feel like the original. If new keys still feel rough, the lock itself may be the issue.
Keep a spare in a safe place and number or label your keys discreetly so you know which is which. Do not put an address on a key ring that could be lost.
Why keys wear faster in South Florida
Climate plays a real part in how quickly keys and locks age. Humidity keeps moisture in the air year round, and that moisture finds its way into keyways. Near the coast, salt in the air adds a corrosive element. Together they dull brass, gum up pins and create a fine grit inside the cylinder. A key moving through that grit wears faster than one moving through a clean lock.
Heat matters too. A key left on a dashboard or in a hot car can warm and cool repeatedly, and while brass is stable, the plating on some keys can flake. A key ring packed with heavy items, such as many keys, a bulky fob and a bottle opener, pulls down on the key as it sits in the lock and presses it against the pins. Over years that extra load wears the key and the lock unevenly. Trimming a key ring to what you need reduces that strain.
Pocket habits play a part. Keys carried loose with coins or tools pick up scratches and burrs. Keys used to open packages, scrape paint or pry at things get bent and nicked. It is worth keeping the house key separate from a general-purpose key ring if you can, or at least keeping the ring light.
None of this requires fussy care. It simply means that in a damp, salty, warm environment, keys and locks are worth checking a little more often than they would be somewhere dry. A quick test of each key with the door open takes seconds, and it catches most problems before they become a lockout.
When rekeying or replacing is the better fix
If a lock is worn but still sound, rekeying or repinning can restore smooth operation along with new keys. Rekeying replaces the internal pins to match a new key, and it often resolves roughness at the same time as changing who has access. It is a good option when you also want to retire old copies.
If the cylinder is badly worn, corroded or damaged, replacement is the better choice. A new cylinder or a new lock set provides fresh pins and a smooth action. If the lock is low-grade and has been in use for many years, replacement may offer better security as well. Our page on rekey versus replace locks explains how a technician decides.
If the door is the issue, adjusting hinges and the strike plate is the fix. A technician can combine these steps in one visit if they are needed. Quotes are given only by phone, and anything complex needs an on-site visit. A service call charge applies to dispatch and is explained before anyone is sent.
When you are ready, call and describe what the key is doing: sticking, grinding, turning part way, needing a lift. The more specific you are, the better the guidance.
A simple maintenance routine
A little attention goes a long way. Once or twice a year, check each key on its lock with the door open. Does it go in smoothly. Does it turn without effort. Does it come out cleanly. If any key does not, replace it. Clean visible grit from the keyway with a dry cloth or a short burst of compressed air. If you use a lubricant, use one made for locks, and use a small amount.
Replace keys that show obvious wear. Keep an original or a high-quality copy for making future duplicates and store it safely. When you have a key made, ask for it to be tested. If you share keys with others, such as a cleaner or a caretaker, label them and keep track.
If you rent out a property, replace tenant keys at turnover or rekey the locks. That resets wear and access in a single step. Our page on duplicate keys and who has copies explains how to track them.
If you notice a lock that is changing, do not wait for it to fail. A short call is easier than a lockout, and a replacement key is easier than an extraction. Call when you are ready, and describe what you have noticed.
Questions people ask
Why does a new copy of my key not work as well as the original?
Copies are cut by tracing or measuring the original, so errors can creep in, especially if the original is worn or the machine is off. A rough cut with burrs can also catch inside the lock. Using a good original as the pattern and testing the copy with the door open helps. If a copy is rough, have it recut.
How can I tell whether the key or the lock is worn?
If only one of several keys sticks, the key is likely the issue. If all keys, including new ones, feel gritty, the lock is probably worn, dirty or corroded. If the lock works with the door open but stiffens when closed, the door alignment may be the cause. A technician can check all three in one visit.
Can I straighten a bent key?
It is better not to. Brass can crack when bent back, and an apparently straight key may still turn poorly. A bent key under force can also snap inside the lock. Replace it with a clean copy cut from a good original, and keep the bent key only if it is the only pattern available.
Is it safe to spray oil into a sticking lock?
Heavy household oils can attract dust and gum up the pins over time. If you lubricate, use a product made for locks and apply a small amount. Do not force the key. If the lock stays stiff after cleaning, call a technician to check for wear, corrosion or a door alignment problem before the key breaks.
When should I rekey instead of just cutting a new key?
Rekey if you want old copies to stop working, if the cylinder is worn but sound, or if you do not know who holds keys. Cutting a new key is fine if you only need a clean spare and the lock works well. A technician can advise, and complicated cases are assessed on-site after a phone discussion.
How are charges handled for a key and lock check?
Quotes are given only by phone. A dispatcher explains how charges work, including the service call charge, before anyone is sent. Straightforward key problems can be described and discussed by phone, while worn cylinders, door alignment or multiple locks need an on-site visit before a firm number is possible.
Describe the situation by phone and we will tell you what the job involves. Quotes are given by phone. Jobs that cannot be quoted without seeing them need a technician on site, and the service call charge is explained on the phone before anyone is dispatched.