IC Cores and Keyways: What "IC Available" Means on a Spec Sheet
, by United Doors and Locks, 4 min reading time
An interchangeable core swaps out in thirty seconds with a control key. What SFIC and LFIC mean, why locks ship without cores, and why the keyway is the real control.
“IC available” appears on almost every commercial lock spec sheet, and it is the line most often skipped. It means the lock accepts an interchangeable core rather than a fixed cylinder — and it is the difference between rekeying a building in an afternoon and rekeying it over a week.
What an interchangeable core is
In a conventional lock, the cylinder is part of the lock. Rekeying means removing the lock, dismantling the cylinder, and repinning it. A locksmith with a pinning kit does this at a bench.
An interchangeable core is a self-contained cylinder that drops into a standard cavity and is retained by a cam. A control key — different from the key that operates the lock — releases the cam and the whole core lifts out. A new core drops in. Thirty seconds, no tools, no dismantling, door stays hung.
The practical consequence: after a key is lost or an employee leaves, you swap cores across the affected doors instead of scheduling a locksmith to repin them.
SFIC and LFIC
SFIC — small format interchangeable core. The figure-eight core, six or seven pins, originally a Best design and now an open industry standard. Multiple manufacturers make compatible cores and housings, keying kits are widely available, and you can hold a stock of cores and key them yourself. Locks such as the Schlage ALX80B SFIC storeroom lever lock and the ALX70B classroom version are supplied prepped for SFIC.
LFIC — large format interchangeable core. Manufacturer-specific and larger, with proprietary keyways. You get the same swap-in-seconds convenience, plus tighter key control, because cores and blanks come through controlled channels. What you give up is the open market: you are buying from one manufacturer for the life of the system.
Neither is better in the abstract. SFIC gives you flexibility and price competition; LFIC gives you key control and a single accountable supplier.
Ordering: locks come without cores
This catches people out. An IC-prepped lock is normally supplied less core — the lock arrives with a plastic construction core or none at all, and the working cores are ordered separately as part of the keying schedule.
So an IC order has three parts: the locks, the cores, and the keying instructions. Miss the third and you receive cores keyed to whatever the supplier's default is. On the LC1200 Series and DB1000 Series deadbolt, the IC variants are separate line items from the standard cylinder versions for this reason — check which you are quoting.
Construction cores are worth using deliberately. Builders get a construction key during the work, and when the building is handed over the permanent cores go in and every construction key becomes useless in one pass.
Keyways and why they matter more than the core
A keyway is the profile of the keyhole. Schlage C is the most common open keyway in North America, and blanks are available everywhere — convenient, and the reason it offers no protection against unauthorised duplication. Anybody can cut another key.
A restricted keyway uses a patented profile. Blanks are only sold to authorised dealers against documented authority, so a key cannot be copied at a hardware counter. If the point of your system is that keys cannot proliferate, the keyway is the control — not the core format.
For genuinely high security, a patented mechanism as well as a patented profile: Abloy Protec2 uses rotating discs rather than pins, which resists picking and bumping in a way conventional pin tumbler cylinders do not, with key control enforced by patent.
Master keying, briefly
Interchangeable cores make master keying practical to maintain. A typical hierarchy:
- Change key: opens one door.
- Master key: opens a group — a floor, a department.
- Grand master: opens every group.
- Control key: removes cores. Not an operating key at all.
Two cautions. Every level of masterkeying adds shear lines to each cylinder, which slightly reduces security and increases the chance of a key operating a lock it was not intended for — so keep the hierarchy as shallow as the building allows. And the control key must be held more carefully than the grand master: whoever has it can remove a core and replace it with one of their own.
When conventional cylinders are the right answer
IC systems carry a premium per lock and require a keying schedule to be designed and documented. For a single tenancy with six doors and one keyholder, a conventional cylinder is cheaper and entirely adequate.
The threshold is roughly this: if you have more than about fifteen doors, or any staff turnover, or more than one level of access, the IC premium pays for itself the first time a key goes missing.
Before you order
Decide the format (SFIC or LFIC), the keyway, and the hierarchy before the locks are ordered, because IC-prepped and conventional locks are different parts. Send us the room list and who needs access to what and we will draw up the keying schedule and quote the locks and cores together.