---
title: "A2 SFIC pinning chart and core calculator · LockCommand"
description: "Free A2 SFIC pinning chart calculator. Type the control key and the operating keys to get the bottom, master, build-up and top pins for a 6 or 7-pin core."
url: https://lockcommand.com/tools/sfic-pinning-calculator
---

[Free tool · no account needed](https://lockcommand.com/tools)

# A2 SFIC pinning chart calculator

Type the control key and the operating keys. You get the bottom, master, build-up and top pin for every chamber of a 6 or 7-pin core, a diagram of both shear lines and a core card to print.

## Core and keys

Schlage manual example, plus a 7th cut

A2 system: depths 0 to 9, .0125" a step, total stack 23.

Bitting as written, tip to bow.

Leave empty for a single-level or two-level core.

## Pins for each chamber

| Chamber | Control \| operating cuts | Bottom | Master | Build-up | Top |
| --- | --- | --- | --- | --- | --- |
| 1 | 5 \| 1, 3 | 1A (.1225") | 2B (.0250") | 12B (.1500") | 8B (.1000") |
| 2 | 0 \| 2, 6 | 2A (.1350") | 4B (.0500") | 4B (.0500") | 13B (.1625") |
| 3 | 9 \| 1, 3 | 1A (.1225") | 2B (.0250") | 16B (.2000") | 4B (.0500") |
| 4 | 4 \| 0, 6 | 0A (.1100") | 6B (.0750") | 8B (.1000") | 9B (.1125") |
| 5 | 2 \| 0, 2 | 0A (.1100") | 2B (.0250") | 10B (.1250") | 11B (.1375") |
| 6 | 7 \| 5, 9 | 5A (.1725") | 4B (.0500") | 8B (.1000") | 6B (.0750") |
| 7 | 4 \| 2 | 2A (.1350") | None | 12B (.1500") | 9B (.1125") |

Every chamber adds up to 23. Build-up = control cut + 10 − the deepest operating cut. Top = 23 − everything below it, which always comes to 13 − the control cut.

Check against your manufacturer's pinning chart before you cap the core.

## Core diagram (change key in)

Bottom (A)  Master (B)  Build-up (B)  Top (B)  Operating shear line  Control shear line

## Core card

A2 core card

Date: ______________

**Door or core**

Room 214

**Core**

7-pin, A2 system, total stack 23

**Control**

5094274

**Grand master**

3616052

**Master**

1236052

**Change**

1230292

| Chamber | Bottom | Master | Build-up | Top |
| --- | --- | --- | --- | --- |
| 1 | 1A | 2B | 12B | 8B |
| 2 | 2A | 4B | 4B | 13B |
| 3 | 1A | 2B | 16B | 4B |
| 4 | 0A | 6B | 8B | 9B |
| 5 | 0A | 2B | 10B | 11B |
| 6 | 5A | 4B | 8B | 6B |
| 7 | 2A | None | 12B | 9B |

Chamber 1 is the first digit as written (tip to bow). Check against your manufacturer's pinning chart. Made with the free SFIC pinning calculator at lockcommand.com/tools.

Add a photo of the core card to the job, with captions, so the core's pinning stays with the customer's record.

[Keep job photos in LockCommand](https://app.lockcommand.com/sign-up?from=tool-sfic-pinning-calculator)

## How to use it

A small format interchangeable core (SFIC) is the figure-eight core that slides out of a Best style lock when you turn the control key. It has two shear lines in every chamber. The operating keys turn the plug at the lower one. The control key turns the plug and the control sleeve together at the upper one, ten steps higher, and that lets the core come out. You can't see either shear line while you pin a core, so it's all arithmetic. This tool does it for the A2 system, used by Best style cores and by Schlage, Arrow, Falcon and KSP cores keyed to A2.

### The A2 pinning rules

1. **Bottom pin** = the shallowest operating cut in that chamber.
2. **Master pin** = the deepest operating cut minus the shallowest. With a grand master you can get two master pins in one chamber.
3. **Build-up pin** = the control cut plus 10, minus the plug total (bottom plus master, which is the deepest operating cut).
4. **Top pin** = whatever brings the stack to 23.

That last step always lands on 13 minus the control cut, so a control cut of 5 always takes an 8B top pin. Schlage's manual says to finish one chamber at a time, start to finish, and that beginners make more mistakes loading all the bottom pins first. In a master keyed core, the tops of the finished stacks should line up evenly below the top of the core. One that sits high or low is a pinning mistake you can fix before you cap it.

### A2 SFIC pin chart

Bottom pins are A pins, .110" plus .0125" a step. Master, build-up and top pins are B pins at .0125" a step, from 1B to 19B. The number on a B pin is how many steps long it is, which is why the arithmetic works.

| Bottom pin | Length | B pin | Length |
| --- | --- | --- | --- |
| 0A | .110" | 1B | .0125" |
| 1A | .1225" | 2B | .025" |
| 2A | .135" | 3B | .0375" |
| 3A | .1475" | 4B | .050" |
| 4A | .160" | 5B | .0625" |
| 5A | .1725" | 6B | .075" |
| 6A | .185" | 7B | .0875" |
| 7A | .1975" | 8B | .100" |
| 8A | .210" | 9B | .1125" |
| 9A | .2225" | 10B | .125" |
|  |  | 11B | .1375" |
|  |  | 12B | .150" |
|  |  | 13B | .1625" |
|  |  | 14B | .175" |
|  |  | 15B | .1875" |
|  |  | 16B | .200" |
|  |  | 17B | .2125" |
|  |  | 18B | .225" |
|  |  | 19B | .2375" |

1B is used only in rare systems that must take in existing keys. Schlage sells no 1B, and its pin list marks 3B, 15B, 17B and 19B as not used in Schlage systems, since pure two-step pinning never needs them.

### A worked example from the Schlage manual

Control 509427, grand master 361605, master 123605, change 123029, bittings read tip to bow. In chamber 1 the operating cuts are 3, 1 and 1. The shallowest is 1, so the bottom pin is 1A. The deepest minus the shallowest is 2, so the master pin is 2B. The control cut is 5, so the build-up is 5 + 10 minus 3, which is 12B. That's 15 so far, and an 8B top pin brings it to 23.

Check chamber 2 of the manual's example yourself. Its text says to add a 10 top pin, but its own stack of 2 + 4 + 4 is 10, so the top pin has to be 13 to make 23. The manual's drawing shows 13, and so does this tool.

You only need the control key, the top master and the change key for most cores. In a well planned system the master keys in between already use cuts from those two, so they work without extra pins. Add a key only if it has a cut the others don't. To plan the change keys for a small system first, use the [master key planner](https://lockcommand.com/tools/master-key-planner).

### A2, A3 and A4: which system is it?

A2 is the one most cores use. The others use bigger steps and fewer depths, so their pins and keys don't mix with A2.

| Spec | A2 | A3 | A4 |
| --- | --- | --- | --- |
| Step | .0125" | .018" | .021" |
| Depths | 0 to 9 | 0 to 6 | 0 to 5 |
| Progression | Two-step | Single-step | Single-step |
| MACS | None | 6 | 5 |

The A2 stack totals 23 and the A4 stack totals 14. This tool only does A2.

### What the warnings mean

- Operating cuts one step apart need a 1B pin. Schlage makes none, and Best uses it only in rare systems. A2 is a two-step system.
- A build-up of 3B, 15B, 17B or 19B is one Schlage marks as not used in its systems. It means the control cut and the deepest operating cut are an odd number of steps apart.
- If every control cut matches an operating cut, the control key would also work as an operating key. Check that against your system's rules.

A2 small format keyways have no MACS, so the tool doesn't check one. Pinning a conventional Kwikset or Schlage cylinder instead? That has one shear line: use the [Kwikset and Schlage pinning calculator](https://lockcommand.com/tools/pinning-calculator).

### Sources

Last checked October 2026.

- Schlage, [Small format cores service manual](https://commercial.schlage.com/content/dam/allegion-us-2/web-files/schlage/technical-documents/Schlage_Small_Format_Cores_Service_Manual_108230.pdf) : A2 depths 0 to 9, the four rules, total stack 23, pin lengths and part list, bittings read tip to bow, and the worked example.
- Allegion, [What is the difference between A2 pinning and A4 pinning?](https://kc.allegion.com/kb/article/what-is-the-difference-between-a2-pinning-and-a4-pinning) : A2 .0125" steps, two-step progression, cuts 0 to 9 and a 23 stack; A4 .021" steps, cuts 0 to 5 and a 14 stack; and [the MACS article](https://kc.allegion.com/kb/article/what-is-the-maximum-adjacent-cut-specification-or-macs) : no MACS for small format keyways.
- Locksmith Ledger, [Mastering IC Pin Stack Mathematics](https://www.locksmithledger.com/locks/cylinders-high-security/article/10228229/mastering-ic-pin-stack-mathematics) : the same A2 method step by step.
- Tyler J. Thomas, [Key Bitting Specifications](https://lsamichigan.org/Tech/KeyBittingSpecifications-TylerJThomas.pdf) (2025): the Best A2, A3 and A4 pin tables, including the rare 1B.

One small difference: Schlage's table prints the 9A pin as .225", while .110" plus nine steps of .0125" is .2225", which is what the spec book prints. The pin numbers don't change. Check against your manufacturer's pinning chart before you cap a core.

## Questions

### What does SFIC stand for?

Small format interchangeable core: the figure-eight core used in Best style locks, which a control key removes from the lock without taking the lock apart.

### What is a build-up pin in an SFIC core?

The pin that sits between the master pins and the top pin and makes the gap for the control shear line. In A2 it is the control cut plus 10, minus the deepest operating cut.

### Why does every chamber add up to 23?

That's the A2 total stack. Allegion lists 23 as the A2 total pin stack, and the Schlage manual has you add a top pin to reach 23 in every chamber.

### Does it work for A3 or A4 cores?

No. A3 and A4 use different steps (.018 and .021 inch), fewer depths and different pin sets. This tool only does A2.

### Which way do I read the bitting?

Type it as written on the bitting list. Small format IC bittings are read tip to bow, and chamber 1 in the results is the first digit you typed.

### Do I need the master and grand master keys?

Only if the core is master keyed. Put in every operating key whose cuts aren't already covered by the others. In a well planned system the change key and top master cover the levels in between.

### Can I pin Schlage SFIC cores with another brand's kit?

Schlage says yes, with exceptions: don't use Arrow bottom pins or Kaba Peaks bottom pins in Schlage cores, and it advises against colored bottom pins.

## More for your shop

- [Pinning calculator Kwikset and Schlage pinning chart: turn a key's cuts into bottom, master and top pins, with MACS checked.](https://lockcommand.com/tools/pinning-calculator)
- [Master key planner Plan a small master key system: change keys by total position progression, pins for every lock and a key schedule.](https://lockcommand.com/tools/master-key-planner)
- [Commercial rekey quote builder Price a building rekey by doors, cylinders and keys, with master key setup, and print the bid.](https://lockcommand.com/tools/commercial-rekey-bid)
- [ID & proof ID and proof of ownership photos, a customer signature and before and after photos on every job.](https://lockcommand.com/features/id-and-proof)

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