Mobile Locksmith · Phoenix & the Valley
IC Core Locks and Control Keys Explained
An interchangeable core (IC) lock has a removable lock core, the part that holds the pins and takes the key, which slides out of the lock when you turn a special control key. Put in a different core and the lock now works with different keys, without taking the lock apart. The control key is not a door key and is not meant to open anything. Its only job is to take cores out and put them in.
That makes IC systems quick to rekey, and it makes the control key the most important key in the building. This page covers the two core sizes, which locks use them, the three key types, what a core rekey involves, and what happens when the control key goes missing.
Do not force the core. Photograph the lock, the core face and any keys you have, then call us. Getting a core out without its control key is a locksmith job. It may involve decoding, drilling or replacing the core, results vary, and we will tell you what we expect once we have seen the door.
What an interchangeable core is
In an ordinary lock the keyed cylinder is part of the lock. To change the keys, someone has to take the lock or cylinder apart and re-pin it. In an IC lock the keyed part is a self-contained unit, the core, that sits in a housing inside the lock and is held there by a retainer. Only the control key releases the retainer.
Pull a core, slide in another one that works with different keys, and the lock is rekeyed. The core you removed can be recombined later on a bench and kept as a spare. Many people call these “Best locks,” because Best, now part of dormakaba, developed the small core that other manufacturers went on to adopt.
SFIC and LFIC: the two core sizes
All IC cores do the same job, but they come in two sizes, and the sizes do not mix.
Which locks take IC cores
The lock needs a housing made for the core. These are the usual places.
- Knob and lever locks. Many commercial cylindrical locks can be ordered with an IC housing. Best’s 9K lever, for example, comes with a standard cylinder or a small-format core.
- Mortise locks. IC housings exist for mortise cylinders, and heavy-duty mortise locks such as Best’s 40H take small-format cores. See mortise locks.
- Exit device cylinders. The rim cylinder on a panic bar can be an IC housing. See panic bars and exit devices.
- Deadbolts, padlocks, cabinet and cam locks, and electrified locks. Schlage’s FSIC, for instance, fits its mechanical, electrified and electronic locks, deadlocks, cabinet locks and padlocks.
Whether an existing lock can be converted depends on the lock: sometimes only the cylinder changes, sometimes the whole lock does. We check the hardware on site before quoting.
Operating, control and construction keys
The rule behind this: a control key should never operate the lock, and an operating key, even a master, should never remove a core. If either happens, something is wrong with the keying or with the key.
How a control key removes a core
Think of the core as having two release points. The operating key reaches the first, which turns the lock. The control key reaches a second, separate one. Turn the control key a short way and the retainer moves clear, so the core slides out of its housing.
The mechanism differs by maker. In small-format cores the control key lines the pins up at a second position, separate from the one the operating key uses. Some large-format designs give the control key an extra cut that works a separate lug. The idea is the same everywhere: a key different from the daily key releases the core.
Why a core will not come out
If a core will not budge, the cause is usually one of these.
- The wrong key. An operating key, even a master, turns the lock but never releases the core. Only the control key does that.
- A control key from another system. Control keys are specific to a format and a system. One from the building next door, or from a different core format, will not release yours.
- A worn or badly copied control key. The thin blades on small-format keys distort when copied carelessly, and a key that is slightly off can fail to engage the release.
- It may not be an IC lock. A conventional cylinder has no release for a control key to work.
Forcing it can wreck a core that could have been saved, so stop and call us.
Why businesses choose IC
- Rekeying without opening the lock. Swap the core and the door is rekeyed.
- Spare cores on the shelf. A lost key or a departing employee becomes a core swap. The pulled core is recombined later.
- Many doors in one system. Master and grand master keying work well with IC across a large building.
- Construction keying. Contractors work on temporary cores, so nobody has to rekey the building afterward.
- In-house swaps. Falcon, for one, states that staff who are not locksmiths can swap cores with the control key. Pinning cores and cutting keys still takes the right kit and records.
IC is common in schools, government buildings and offices, and in other buildings where keys change often. See our school locksmith page for campus work. It is not right for every building. With a few doors and little turnover, a conventional cylinder, ideally on a restricted keyway, is simpler. IC tends to pay off with many doors, frequent key changes or a master key hierarchy.
IC cores and key control
An IC core makes rekeying fast. It does not, by itself, stop anyone from copying a key. That depends on the keyway. On an open keyway, blanks are sold by locksmith suppliers, so keys can be copied by anyone who can buy and cut them. Restricted and patented cores exist, from makers such as Schlage and Medeco, and pairing one with signed key records is what gives you real control. Our master key systems page explains restricted keyways and why a “Do Not Duplicate” stamp does not do the job.
What a core swap or rekey involves
Swapping a core
With the control key, you pull the old core, slide in a spare that already works with the keys you want to issue, and test it. It is quick, and it is the part a customer’s own staff can often do.
Rekeying (recombining) a core
Recombining means changing the pin stack inside the core to match new keys. On a small-format core the core is pulled, all the pins and springs are removed, the new stack is loaded from the keying schedule, a new spring cover is seated and every key is tested. Large-format cores are closer to re-pinning a conventional cylinder. Pin sizes come from the bitting list. In a master keyed system the stack also carries extra pieces for each level, so the schedule has to be right. Falcon states that it can supply cores already combined to match an existing Best or Arrow system when it is given the bitting list.
What takes more than a control key: pinning the cores needs a kit and the bitting records, and new keys need the correct blanks (small-format keys have thin blades that distort in a careless copy). That part is normally locksmith work. Our commercial rekey and master key systems pages cover the wider job.
If the control key is lost
When the control key is gone, getting a core out becomes a locksmith job. Results vary, and we will not promise a clean outcome before we have seen the door. These are the realistic options.
- Records. Start with whatever records you have, such as a keying record or bitting list from the original installation. Whether a replacement control key can be obtained, and what proof of ownership it takes, depends on the brand.
- Removing the core without the key. Sometimes a locksmith can get a core out without damaging it. Sometimes the work involves decoding the combination so a key can be made. Sometimes the core has to be drilled, which destroys it. Which one applies depends on the lock, the format and the core’s condition.
- Replacing cores or housings. If a core cannot be saved it is replaced, and a damaged housing is replaced too.
- A new control key afterward. Treat a lost control key like a lost master, because whoever holds it can remove your cores. The fix is a new control key combination, which means recombining or replacing the cores.
Looking after the control key
In a master keyed IC system the control key is a single point of failure, so treat it that way.
- Record its stamp or identifier and who holds it.
- Keep it locked up, with a sign-out sheet.
- If you keep a spare control key, record it and store it separately.
- Do not lend it to vendors or cleaning crews. If a core needs pulling, have someone from your side do it, or call us.
- If you cannot say where it has been, count it as lost.
Mixed core formats
Many buildings end up with more than one kind of lock: small-format cores on some doors, large-format on others, conventional cylinders in an addition. A few rules help.
- A core fits only a housing made for its format. For large-format, that usually means the same maker as well.
- Control keys are specific to a system and a format.
- Whether one set of keys can run across formats depends on the keyway family. Some restricted families are made to span conventional, large-format and small-format cylinders. Schlage says its Everest 29 SL does. Other systems cannot, so check before mixing formats.
- When adding doors, matching what is already installed usually matters more than choosing the best brand.
- The face of the core, close up, with any letters or numbers stamped on it.
- The whole lock, front and side, including any brand name on the lock body or around the cylinder.
- Both sides of the key head, with any stamps, letters or brand names. Your operating keys and your control key.
- A spare core, if you have one.
- How many doors have IC locks, and how many spare cores you hold.
- Where the control key is kept and who has used it.
On some systems the control key’s head is shaped differently from the operating keys, so an odd key in the drawer that opens nothing may be the control key. Our guide to key types shows what common keys look like.
Working on an existing IC system
Send photos of the core, the lock and your keys through the commercial quote page, or call (602) 301-5243, and we will tell you what is involved and whether your system can be serviced on site. That depends on the format, the keyway and whether you have the control key. Restricted keyway systems are controlled by the manufacturer, so ask us early whether we can get keys and cores for yours. If the job is a very large multi-building system, tell us up front and we will say whether one technician is the right fit. Our commercial locksmith page lists everything else we do for businesses.
Frequently asked questions
Control key needed: what does that mean?
It means the core is held in the lock by a retainer that only the control key releases. Your normal door key, even a master, will not remove it. If you do not have the control key, check with whoever installed or last serviced the system, then call us with photos of the lock and the keys. Without it, getting the core out is a locksmith job.
I can’t get the core out. What is wrong?
The most common cause is the wrong key: an operating or master key instead of the control key, or a control key from a different system or core format. A worn or badly copied control key can also fail. Do not force it or use pliers, which can damage the core. Photograph the lock and the key and call us.
Do I need the control key to rekey an IC core?
For a normal rekey, yes. The core has to come out, and the control key does that. With it, rekeying means recombining the core, which needs a pinning kit and the bitting records. Without it, rekeying turns into a different job that may involve decoding, drilling or replacing cores, and results vary.
IC core vs standard cylinder: which is better?
IC suits buildings with many doors, frequent key changes or a master key hierarchy, because a rekey becomes a core swap. A standard cylinder, ideally on a restricted keyway, is simpler for a few doors with little turnover. Door count, staffing and what is already installed decide it. We will tell you which we would pick.
What is the difference between SFIC and LFIC?
SFIC is the small figure-8 core in a standard size that many makers build to, usually 6 or 7 pins. LFIC is the large format, and each maker’s version, such as Schlage’s FSIC, is built for its own housings, with limited crossover between makers. Small-format rekeying uses a special kit and new spring covers. Large-format is closer to pinning a standard cylinder.
Can I convert my existing locks to IC?
Sometimes. If the lock has a replaceable cylinder, such as a mortise lock or the rim cylinder on an exit device, it can often take an IC housing. If the cylinder is built into the lock, the whole lock may need replacing. We check the hardware on site before we quote, so you know which doors are which.
How do I know if my lock uses an IC core?
Look at the face of the cylinder. A small-format core has a figure-8 outline, and a large-format core is a larger version, though not every lock shows it clearly. Photos of the lock face, the lock body and both sides of the key heads let us tell you what you have. A key in your records that opens no door may be the control key, which is a strong sign of an IC system.
Related commercial services
Talk to the locksmith who does the work.
Call (602) 301-5243, Monday to Friday, 8:30am to 6pm. For bigger projects we look at the doors first and agree on the price before any work starts.
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