SFIC Pinning Calculator
Enter the control key, master key and change key bittings for a small format interchangeable core. The calculator returns the bottom, master, control and top pin for every chamber, checks that each stack adds up, and flags pins that are too thin to use.
SFIC pinning chart
| Pin # | Bottom pin | Master / control / top pin |
|---|---|---|
| #0 | .110 | — |
| #1 | .1225 | .0125 |
| #2 | .135 | .025 |
| #3 | .1475 | .0375 |
| #4 | .160 | .050 |
| #5 | .1725 | .0625 |
| #6 | .185 | .075 |
| #7 | .1975 | .0875 |
| #8 | .210 | .100 |
| #9 | .2225 | .1125 |
| #10 | — | .125 |
| #11 | — | .1375 |
| #12 | — | .150 |
| #13 | — | .1625 |
| #14 | — | .175 |
| #15 | — | .1875 |
| #16 | — | .200 |
| #17 | — | .2125 |
| #18 | — | .225 |
| #19 | — | .2375 |
| #20 | — | .250 |
| #21 | — | .2625 |
| #22 | — | .275 |
Sources: SARGENT Small Format Interchangeable Core — Standard & XC Feature Keying & Assembly Manual (Rev. March 2006), pp. 4–6, 14, Schlage small format cores — Service manual 108230 (Rev. 01/18), pp. 9–11, Schlage SFIC Service Manual, Second Edition (June 2000) — pin lengths
| Pin # | Bottom pin | Master / control / top pin |
|---|---|---|
| #0 | .110 | — |
| #1 | .128 | .018 |
| #2 | .146 | .036 |
| #3 | .164 | .054 |
| #4 | .182 | .072 |
| #5 | .200 | .090 |
| #6 | .218 | .108 |
| #7 | — | .126 |
| #8 | — | .144 |
| #9 | — | .162 |
| #10 | — | .180 |
| #11 | — | .198 |
| #12 | — | .216 |
| #13 | — | .234 |
| #14 | — | .252 |
| #15 | — | .270 |
| Pin # | Bottom pin | Master / control / top pin |
|---|---|---|
| #0 | .110 | — |
| #1 | .131 | .021 |
| #2 | .152 | .042 |
| #3 | .173 | .063 |
| #4 | .194 | .084 |
| #5 | .215 | .105 |
| #6 | — | .126 |
| #7 | — | .147 |
| #8 | — | .168 |
| #9 | — | .189 |
| #10 | — | .210 |
| #11 | — | .231 |
| #12 | — | .252 |
| #13 | — | .273 |
How SFIC pinning works
Each chamber of an interchangeable core has two shear lines: one for the operating keys and one for the control key. The calculator builds every chamber the same way, from the bottom up:
- Bottom pin = the shallowest operating cut in that chamber.
- Master pin(s) = the differences between the distinct operating cuts, from shallowest to deepest. If every operating key has the same cut, there is no master pin.
- Build-up pin = control key cut + control constant (10 for A2, 7 for A3, 6 for A4) − the deepest operating cut.
- Top pin = whatever brings the stack to its total: 23 for A2, 16 for A3, 14 for A4.
Example, A2, one chamber: control cut 5, operating cuts 1 and 3. Bottom pin #1, master pin #2 (3 − 1), build-up pin #12 (5 + 10 − 3), top pin #8 (23 − 1 − 2 − 12). This is chamber 1 of the worked example in the Schlage small format core service manual (p. 10), and the calculator reproduces that example chamber for chamber.
The constants come from the Sargent SFIC keying manual and the Schlage manual. See About for how the data is checked.
Frequently asked questions
What is an SFIC?
SFIC stands for small format interchangeable core: the figure-8 shaped core that can be removed from its lock housing with a control key and swapped for another core. The format was introduced by Best and is also made by other manufacturers, including Schlage and Sargent, to the same pinning systems.
What is the difference between A2, A3 and A4?
They are three pinning systems for the same core. A2 uses a .0125" step between pin sizes with key depths 0 to 9; A3 uses .018" with depths 0 to 6; A4 uses .021" with depths 0 to 5. Every pin stack adds up to 23 in A2, 16 in A3 and 14 in A4, and the control constant is 10, 7 and 6 respectively. Most SFIC systems in the field are A2.
Why does every chamber add up to 23?
In an A2 core every chamber has the same total stack height: bottom pin + master pin(s) + build-up pin + top pin = 23 units of .0125". That fixed total is what lets you calculate the top pin last, and it is a quick check on your work: if a chamber does not add up to 23, one of the pins is wrong.
What is a build-up (control) pin?
An SFIC has two shear lines in each chamber: one for the operating keys (change, master, grand master) and one, higher up, for the control key that removes the core. The build-up pin spans the distance between them. Its size is the control key cut plus the control constant (10 in A2) minus the deepest operating cut in that chamber.
Why does the calculator warn about #1 pins in A2?
A2 master, build-up and top pins start at #2 in the manufacturer pin tables, so a stack that needs a #1 pin cannot be built with standard A2 pins. When that happens the calculator still shows the result but flags the chamber, so you can change the bitting. In A3 and A4 the smallest master pin is #1, so no warning is given there.
Does the calculator check MACS?
Not for SFIC. None of the manufacturer documents we use state a maximum adjacent cut specification for these systems, and we do not apply limits we cannot source. Check your key machine and the manufacturer documentation for your keyway.
Is the bitting I enter sent anywhere?
No. All calculations run in your browser. Bittings are not sent to a server, not put in the page address, and not saved in cookies or local storage. Reloading the page clears them.
How do I keep a copy of the result?
Use your browser's print function (Ctrl+P or Cmd+P). The page is laid out for printing: navigation and buttons are hidden, and the keys, warnings, pin table and pin diagram fit on the first page.
Can it work out a bitting from a key code?
No. LockSpecs does not provide key code to bitting lookups. The calculator only works from bittings you already have.