How to Re-Pin a Cylinder Tumbler Lock

Remove the cylinder tumbler lock you want to re-pin from the door it is fitted to. Unscrew it from the mounting from the inside and disassemble the cylinder from any other parts of the housing with a screwdriver.

Remove the restraining clip at the back of the cylinder. Different manufacturers of cylinder tumbler locks use different types, but they are mounted at the opposite end of the cylinder to where the key enters the lock. Some will snap off easily, but if yours does not, place the lock in a vise and knock it off with a screwdriver and hammer. Remove the spring cover panel that is located on the top of the lock cylinder. You may need to bend some metal tabs back with a screwdriver to do this. Once you remove the cover, you will see some holes running in a row along the cylinder.

Insert the key that operates the lock and give it a quarter turn. Pull the key out of the cylinder and the lock plug should come out of the cylinder with the key. Push from the far end with a screwdriver, if it does not come out first time. Once the lock plug is removed, turn it upside down so that the key springs, driving pins and key pins fall out.

Remove your key from the lock plug and insert a new one. This is the key to which you will re-pin the lock. Hold the lock plug so that the holes in it are face up. Drop a new key pin into each of the holes so that each key pin stands as flush with the top of the lock plug as possible. To prevent jamming, ensure each key pin has the tapered end facing down, since this is the end that will come into contact with the key when it is inserted into the lock.

Remove the key from the lock plug, keeping the holes upright. Insert a driving pin into each of the holes. Make sure that each driving pin sets on top of the corresponding key pin so that it is sunk into the hole but stands out of it. About 1/8-inch of the driving pin should be exposed, with the rest of it setting inside the lock plug. Remove the driving pins one at a time, making a note of which one goes in which hole. Ensure the key pins remain in the lock plug.

Insert your new key into the lock plug. Push into the lock cylinder, being careful not to spill any key pins. Drop the driving pins into the holes of the cylinder. These are the holes you exposed by removing the spring cover panel. Place one driving pin per hole in the same order as you removed them from the lock plug. Holding the cylinder horizontally, remove the key. The lock plug should now be in a locked position within the cylinder.

Drop a key spring into each of the holes in the cylinder. It is possible to reuse the ones you removed from the cylinder earlier. Remount the spring cover plate onto the top of the cylinder and bend any restraining tabs back in place to ensure the cover does not come loose. Refit the lock plug's restraining clip. You may need to use pliers to bend it back onto the housing.

Test the lock with your new key. If it works without having to jiggle it around, remount the cylinder tumbler lock into the housing.