Servicing Interchangeable Cores

May 2, 2018
Code production, pinning procedures, service tips, tools, and resources to help you thrive

Market changes we discussed last month create remarkable new commercial opportunities for the locksmithing industry. SFIC dominance in large systems, plus distribution upheaval are driving rapid change. (See Interchangeable Core Systems Bring Opportunities for Growth,

You can now purchase original equipment materials to service school districts, colleges and universities, military bases, hospitals, utilities, manufacturing plants and transportation hubs that use Small Format I/C cores.

When Frank Best developed the SFIC system in the 1920s, his market focus was on large organizations with their own professional lock shops. Since independents didn’t generally serve this market, trade distribution channels just didn’t exist.

As the I/C core market grew, other brands and aftermarket suppliers offered their own versions of I/C cores, keys and pin segments. One of the most successful has been LAB Security Systems, founded by Robert Labbe in 1956. Today, LAB produces more than 1.3 billion pin segments annually, serving much of the industry for large and small format I/C and standard cores.

Eventually, the SFIC core became the “open architecture” standard, from North American sources. Pockets of LFIC systems followed some very successful construction hardware dealers, who effectively served their customers.

The following article reviews code production, pinning procedures, service tips, tools, and resources to help you thrive in this rapidly changing market. We’ll focus on standard SFIC cores since they dominate the I/C market, and the procedures are common throughout the industry.


Codes are typically produced and recorded by the manufacturer. It is extremely wise to stay with their system and not get creative. In one case a locksmith was excited to discover he could gain many additional key changes by using the GM code for operating cuts in one of the barrels. A few months later, he was looking for a new job, as his employer was forced to relock an entire campus.

Manufacturers don’t duplicate a GM or Control system within reasonable distance for a given keyway.   These geographical restrictions are not published, so go to the source rather than inventing your own systems. Your worst nightmare is duplicating a large system across the street.

Factory or distributor-sponsored masterkey training sessions are strongly recommended. You will learn important details and gain valuable practice so you can avoid “account killing” mistakes.  Here are links to ASSAABLOY (ASSA, Corbin/Russwin, Medeco, Sargent), Best and Schlage authorized training sessions: Many are offered at very low cost.

The Locksmith Security Association of Michigan website below, contains a large library of training manuals, and an excellent Master Key System Design Guide. The Best Core and Key Service Manuals available on the factory website below, may be the most detailed. The Best “Support” section has an extensive “Knowledge Base.”

How does SFIC pinning work ?

There are three basic SFIC systems; the A2, A3, and A4. Many manufacturers do have additional levers, sidebars, notches or other devices, not covered here.

The A2 system is overwhelmingly dominant since it provides 16,384 useable key cuts plus masters in a 7-bbl system (4 to the 7th power) with no restrictions, has a great deal of flexibility, and logical mathematical progressions. The cuts go from 0 to 9 and are in .125” increments, using only even or odds in a given bbl (giving .250” minimum between cuts). Cuts in a given bbl are rotated from the GM.  Look over the Best training manual and you’ll see the change key rotations and progression on a sample code sheet. This mathematical logic often allows you to reconstruct a degraded system. A note of caution: A number of independent locksmiths have lost accounts by inventing their own rotation protocol.

The Best website has excellent A2 & A4 pinning worksheets. The link below also has a simple pinning chart, showing the pin stack when the CT, GM, and the change key are input. A smartphone version is also available from (

Never never never ever mix even and odd codes within a given barrel in an A2 system. A specific bbl will use all even or all odd codes. When you’re doing the math, a bbl may have even and odd pin segments (rather than codes), so don’t confuse those two issues.

The A3 system provides a whopping 279,936 codes in a 7 bbl SFIC core. New A3 systems are no longer available as the .0180 spacing is too close between cuts to be secure as core and pins wear.

The A4 system provides 78,125 operational codes in a 7 bbl SFIC core (5 to the 7th power) with .021” spacing. Scrambled codes are printed by manufacturer. Since the A4 system uses all the codes in a given bbl, you don’t have the option to re-key by simply changing two or three bbls from even to odd numbers or odd to even as you can with the A2 system. A2 is by far the most popular.

Which cores and pin segments should we use ? This writer has heard every perspective from one end to the other. The short answer is: you can’t go wrong using pins made for that core. This goes for LFIC, SFIC, and specialty cores. One person commented that some people want less expensive parts, and others want to be sure the customer is happy. What about colored pin segments?

LAB makes different pin segments for different applications and for many original equipment manufacturers. Hardened brass is used for the popular colored pin segments. The hardened brass bottom pins tend to work fine in low traffic applications. LAB recommends nickel silver bottom pin segments for use with nickel silver keys and for higher traffic doors. Best-specific pins are recommended for close tolerance Best cores. Lab also produces universal pins for others.

Best Access has learned a lot about matching pin segments and keys during their near century of building SFIC cores. All bottom pin segments from Best are nickel silver to accommodate the nickel silver keys and tight tolerances. The Best type bottom pin segments have a specific top bevel and flat bottom tip that works well with the tight tolerances of their keys and cores. Most manufacturers produce spool, drill and tamper resistant pin segments.

In addition to the Original Equipment Manufacturers, KSP, Marshall Best, and Oak Security provide SFIC cores pins, housings and service equipment.

We’ll not cover the pinning procedures here, as they are covered in the training manuals and in the hands-on classroom. If you have numerous customers in your area with Corbin/Russwin, Sargent, Schlage, or Yale LFIC cores, by all means attend an appropriate class. Since you likely have a lot of customers (or prospects) with SFIC cores, you will want to contact your wholesale distributor or a respected SFIC manufacturer to get into one of their classes. These inexpensive classes give you confidence to get the job done – right.

Service Parts

Best, Schlage, Arrow and others offer complete lines of SFIC service equipment – key cutters, pinning kits, capping blocks, ejectors, key gauges, etc. Texas based A-1 Security Mfg. ( makes the original Best key cutter and capping presses.

HPC ( (left) and Peterson Locksmith Tools provide SFIC drill jigs that clamp onto a key for an accurate drill position. (

Pro-Lok ( offers a handy I/C rekey, decode, and dump tool (Right).

Major Manufacturing ( builds hand capping tools for Corbin/ Russwin and Sargent LFIC cores. KSP is also a well known supplier of SFIC cores, pin segments, service parts, the Falcon style SFIC core with slide top cap, and Schlage LFIC housings. (

Service Tricks

Some SFIC brands will have looser tolerances to accommodate various pin segments and key cutters.   With tighter tolerance SFIC cores, Best-specific pins, and with accurate flat-bottom cuts, your keys will be more accurate. However, key insertion and removal will be much more crisp than in residential hardware. Users of close-tolerance SFIC cores learn to wiggle the key just slightly as it is inserted or removed. This slight vibration allows easy pin movement.

When re-pinning, hold a core upside down on a piece of carpet while you punch out as many bbls as necessary with the pin ejector. Decode and dump tools discussed earlier, make this easier in the field. In many cases a new core may be difficult to turn. After lubrication, use only a small plastic or wood hammer to tap gently on the side of the thin brass sleeve as you rotate the key.   A key and core stamping plate is also very handy in the shop or field. A carpet underneath reduces bounce.

Sometimes a CT, GM, or operating key won’t work in a new core. First, check the key against a gauge for correct cuts. Next, check the math on your pinning work sheet. Finally, insert a pin ejector into the bottom, compressing the spring and measuring the depth of each bbl. You are likely to find one bbl that goes deeper or not as far as the others. Nine out of ten times, repining that bbl will solve the problem.

Occasionally, dirty cores prevent pin segment movement.   Two culprits come to mind. The first is using WD-40 as a lubricant. This product does lubricate and free things up, but the fish oil has not proved an effective long-term core lubricant. The second problem is mixing dry (graphite) and liquid lubricants. If a key is trapped and just doesn’t want to come out, squeezing the key between thumb and forefinger will keep just enough pressure on the plug face to relieve stress on the pins, allowing extraction. Try that before drilling.

Frequently use a key gauge to compare your cuts to factory keys. You may be shocked at the results. It’s a good idea to check this on occasion. Things drift.

With very high traffic or years of use, the front bbl (at the face) of the core can begin to deform. When this happens, core operation will become increasingly difficult as the pin segments begin to tilt. It’s time for that core to go to the brass scrap heap.


On rare occasions, you have no choice but to drill a core out. Practice this in the shop a couple of times before trying it in the field. 1. Take a 1/8” drill bit, marking the depth you need to reach the inside rear of the core. You do not want the drill bit to exit the back. 2. Mark a spot and drill just below the face logo, which is where your bit will intercept the Control shear line. 3. Use a lock pick to rake debris out of the drilled hole. 4. Use a medium sized flat head screwdriver to turn the locking lug 15 degrees to the right. A pair of needle nose pliers will then usually pull the core. Cores with drill-resistant steel pins will need to have the locking lug itself drilled out at the side.

You’ll learn several other important service tips at a hands-on class. It may prove to be one of the more valuable things you’ve done in your professional career.

Cameron Sharpe, CPP wrote for Caterpillar and Honeywell before working 25-years in hardware and electronic access distribution. [email protected]