Rekeying a pin tumbler lock:
Most pin tumbler locks are built on the same principles. The main parts of the lock are the cylinder and the latch. The cylinder is built from two main parts – the cylinder housing and the cylinder plug. In order to understand how to rekey a lock, you must first understand how a lock works. In general you have the cylinder plug which can be seen on the outside of a lock as the keyhole area. When you insert the correct key inside the keyhole the key lifts the bottom pins up until they are perfectly aligned with the sheer line between the cylinder plug and the cylinder housing. Once they are aligned there is nothing preventing the cylinder plug from turning. Each one of these bottom pins can be of different height and therefore a common lock which typically holds five pins can have thousands of possible combinations. The bottom pins are also shaped in a certain way, they are small cylinders with one pointy end and one flat end, and resemble the shape of a bullet. The pointy end is the part that faces down and is in contact with the key once inserted. Above the bottom pins are top pins which unlike the bottom pins, they are flat on both ends and are normally all equal in size for each particular lock. Above the top pins you will find springs. These springs are made to place constant force on the top pins which also place force on the bottom pins. All the springs in a lock are of the same size and have the same amount of pressure. Now that we understand a bit more about the anatomy of a lock, we know that the only thing that makes a lock work with the right key is in fact the bottom pins. So in order to rekey or match a new key to a lock, all that is needed to do is replace the bottom pins only. In order to replace the bottom pins you must first release any screws or clips holding the cylinder plug to the cylinder housing. Then you must insert the correct key and turn the cylinder plug to an angle where the bottom pins are no longer in contact with the top pins. Then you must use a locksmith tool known as a cylinder follower. This tool is usually a brass tube and is made to push the plug outward while at the same time holding all the top pins and springs in place. You would need to slide the follower from the back end of the cylinder against the cylinder plug until the plug is completely out of the cylinder and the follower has taken its place. Now you must match a new key to the plug. For this stage you would need a pinning kit. A pinning kit would be a kit which includes all the variation of bottom and top pins required to rekey most locks. These pinning kits normally have all the codes referring to the different sized pins for different brand locks. For instance a number 2 bottom pin on a Kwikset lock would be 0.195 .Some keys have a numeric code engraved on them which represents the pins that need to be placed in the lock for it to match the key. If you do not have a numeric code on the new key you can insert the key in the plug and load one pin at a time until you find pins that are aligning with the surface of the key plug. Once you have all the correct bottom pins you need to insert the cylinder plug back into the cylinder housing the same way it was pulled out earlier. Once back in, you need to attach the screw or clip that holds the plug to the housing. Test your new lock with the new key and see that it turns smoothly. If you didn’t match the correct pins, the key might be a bit stiff to turn or will not turn at all.