Spare Key Making for Homes and Cars

Why spare keys fail more than people expect

Most people assume a copy is as good as the original. In practice, copies fail at a surprising rate, and the reason is usually accumulated error. A key is a small piece of metal with cuts measured in thousandths of an inch. A copy made from a worn original inherits the wear. A copy made from that copy carries both the wear and any cutting error from the first duplicate. After a couple of generations, a key may turn stiffly, catch on the way in, or work only when you lift or jiggle the door.

The lock suffers too. A poorly cut key drags across the pins inside the cylinder, and that wear shortens the life of the lock. A key that works badly on the first day sometimes seems fine, then breaks off in the cylinder months later when the metal fatigues. Nobody connects the broken key with the copy shop visit, but the connection is real.

The remedy is not complicated. Make copies from the best key you have, not the oldest. If your only key is worn, there is another path that does not depend on its cuts at all, and the technician can discuss it with you on a call.

Copying from a worn key and the alternative

If your house key has been in use for years, the edges are probably rounded, the grooves may be dirty, and the cuts may no longer match the original. A duplicating machine traces the key you provide. It cannot know what the key should have looked like. It simply reproduces what it reads. A worn key becomes a worn copy.

A locksmith can instead read the cuts of the lock itself or work out the key cuts from the cylinder. This produces a fresh key to the original specification, which usually works better than a trace of a tired one. It is a different process from simple duplication and may need a visit to the lock. For some situations, rekeying the lock to a new key is a cleaner option, and you can read how that works on the rekeying page.

If a key is bent, it should not be duplicated. Do not try to straighten it with pliers, since that can crack the metal. A bent key may be near the end of its life, and the correct approach is to replace it from the lock's information rather than trace a damaged shape.

Key blanks and why quality matters

A blank is the uncut key before any grooves are made. Blanks vary in alloy, finish, thickness and accuracy. A good blank is made from a brass alloy that holds its shape, has a clean finish and matches the specification for the keyway. A poor blank may be softer, slightly off-size, or rougher, which makes the finished key wear faster and bind more often.

For house keys, the usual blank is brass or nickel-plated brass. Nickel plating helps resist corrosion, which matters near the coast where salt air attacks metal. In humid South Florida, a key kept in a pocket, a car or a beach bag deals with moisture all the time. Surface corrosion can build up in the keyway of both the key and the lock, and a better finish helps.

For car keys, the blank is only part of the story, since many modern keys include a chip. A cut blade alone will open the door on some cars but not start the engine. If your car key has a plastic head, it probably contains a transponder, and the chip must be programmed. The related page on transponder key programming goes into that work.

• Ask which blank is used and whether it matches your keyway.
• Prefer a blank with a clean, uniform finish, without burrs or rough edges.
• Test every new key in the lock before you leave, not later at home.
• Keep the original key out of daily use once spares exist, so it stays accurate.

Test the copy properly

A copy that slides in and turns once is not necessarily a good copy. Test it several times. Insert it fully, turn it, remove it, and repeat. Check that it turns without force, that it does not catch on the way in or out, and that the door latches and unlocks as it should. Test on the actual lock you intend to use it on, with the door open and then with the door closed and the lock under load from the weather stripping.

If the key needs wiggling or lifting, it is not a good copy. Do not accept the explanation that it will wear in. A well cut key should work smoothly from the first turn. If it does not, have it recut or made again from a better source.

Doors that sag, which is common in older homes in humid climates, can make any key feel stiff. Part of testing is checking whether the problem is the key or the door. Try the original key in the same lock. If the original works and the copy does not, the copy is the issue. If both feel stiff, the lock or the door may need attention, and a technician can advise.

Who needs spares and how many

A household usually needs one key per adult, plus a spare kept in a safe place, plus a key for a trusted neighbor or relative who might need to reach the home in an emergency. Beyond that, extra copies multiply risk, because every key is a path into the home. Think of copies as access you hand out, and keep a short list of who holds one.

Families with teenagers, caregivers, cleaners or contractors often end up with many copies and no record. That is a common reason for rekeying later. If you cannot say who holds a key to your front door, it may be time to start fresh, and there is a related discussion in the guide on rekey versus replace.

For cars, two keys is a reasonable minimum. A second key lets you recover if one is lost, and it spares you the longer process of an all keys lost call. If your car has only one key, adding a second is a good use of an appointment.

Labeling without creating a risk

It is tempting to label a key with your address so it is easy to find. Do not. A lost key with an address attached is an invitation. If someone finds it, they know exactly where to use it. Instead, use a marking only you understand, such as a color or a number that means something to your family, and keep the master list at home.

A good system is short. Mark keys by door or by purpose using a coloured cap or a small tag, and keep a written list in a drawer or a document that says what each mark means. When a key goes missing, you know which lock is affected and how serious the situation is.

Keep car keys away from the house key ring when you hand a vehicle to a valet or a repair shop. A valet does not need your house key, and a repair shop does not either. Separate rings avoid the temptation of making a copy, and they avoid a lot of avoidable worry.

Where to store spares, and where not to

Storing a spare under a mat, in a flower pot, on top of a door frame or in a fake rock is a habit that many people share and burglars know about. The topic gets its own guide, why hiding a spare key fails, and the short version is that a hidden key is not really hidden. Anyone who wants to look will look in those places first.

Better options include giving a spare to a trusted person who lives nearby, keeping one in a secure place inside your home, or using a good quality lockbox with a combination you control. Our lockbox and key safe guide covers what to look for. A lockbox is not a perfect answer, but it is more reasonable than a hiding place that anyone can discover.

For vacation homes and rentals in the area, spare keys travel more than most. Keep a record of who has one, and change locks or rekey between significant changes of guests or caretakers. This costs less than a security problem, and it keeps the control with you.

Examples of spare key problems

A retired couple in an east Delray home has used the same house key for many years. When they ask for a copy from a hardware store, it works poorly, and the new copy sticks in the lock. The technician examines the original, finds it badly worn, and offers to cut a fresh key from the lock's information. The new key turns easily, and the old key is retired.

A property manager in Boca Raton hands out a key for each new tenant but never collects them. After a few turnovers, nobody knows how many copies exist. The manager chooses to rekey the unit and make a small set of new keys, which restores control at a reasonable level of effort. Our apartment turnover rekey page describes this routine.

A family returns from a trip to find that their car's only key has been lost on the beach. They did not have a spare. The process of replacing the key takes longer than a simple duplicate would have, and costs more of their day. They now keep a second key at home.

Different keys, different duplication paths

Not every key in your pocket is copied the same way. A standard house key is cut on a duplicating machine that follows the original. A dimple key, which has round indentations instead of ridges on the blade, needs a different machine. A key for a high security cylinder may have a side track or a sidebar profile that standard equipment cannot reproduce. A padlock key, a mailbox key and a file cabinet key are often small blanks that need their own holders and cutters.

Car keys add more layers. A basic metal car key can be copied like a house key. A key with a plastic head probably contains a chip, and a remote head key adds buttons. A smart key is a different category altogether, covered on the push-button start key page. Before you pay for a copy, know which category yours belongs to.

Tell the technician what the key opens and whether it has any markings, numbers or colors. Those details narrow the options quickly. If you carry a key you cannot identify, bring it along. Many keys that look unusual turn out to be ordinary once a trained eye sees them, and some that look ordinary turn out to be controlled.

Humid air, salt and key wear in South Florida

Keys here live a hard life. A key ring may go from an air-conditioned car to a humid walkway to a beach bag in one afternoon. Moisture and salt build up in the grooves, and brass can darken and pit over time. A pitted key can catch inside the cylinder, and the residue that comes off can gum up the pins.

A simple habit helps. Wipe keys with a dry cloth after a beach trip, and let them dry before they go back in a pocket. If a key looks green or white at the edges, that is corrosion, and it is a good reason to make a fresh copy before the key fails in the lock. See the guide on caring for locks in salt air for related habits.

Consider making copies of your most-used keys on a regular basis, and retire the oldest. A key that has been in daily use for years is a candidate for replacement long before it breaks. Making a fresh set while the old key still works is a calm, low-stress task, compared with doing it after a failure.

Keys that cannot be copied everywhere

Some keys are marked with a notice that says do not duplicate. That marking is not a legal block in most cases, and a shop that copies the key may do so without issue, but it is a signal that the key belongs to a managed system. A building with a master key system or a restricted keyway wants to control who has copies, and a stray duplicate undermines that.

Truly restricted keys are different. They use controlled blanks that are only supplied to authorized people, and copies require a request from someone with the right to make it. The page on restricted key duplication explains how authorization works.

If you are not sure whether your key is restricted, ask. A technician can look at the key and tell you whether it is a standard blank or a controlled one. If it is controlled, the process is different, and it is better to learn that before you plan around a quick copy.

Quotes, service calls and what to ask

Pricing for key duplication depends on the key type. A plain house key is different from a high security key, and both differ from a car key with a chip. Quotes are given by phone, after the technician learns what you have. Complicated jobs may need an on-site visit, and a service call charge applies for dispatch and is explained on the phone before anyone is sent.

When you call, describe the key. Say whether it is a house key, a car key, a padlock key or a mailbox key. Mention any markings on the head. Say how many copies you want, and say whether the original is worn. These details help the dispatcher choose the right approach.

Ask whether the work is cut on site, whether the key is tested in the lock, and whether you will get the original back with the copies. Ask also what happens if a copy does not work. A trustworthy locksmith will say it plainly and will recut or remake a copy that fails.

When you are ready to make spares for your home, your car or your business, call and explain what you have. The person on the phone can explain the options and what the visit would involve.

Questions people ask

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