If you are going to remove a door lock to replace the cylinder you will need the key to remove the cylinder. Unfortunately, most times that you will need to remove the cylinder will be because you have lost the key to the lock. Most locks, however, can be quickly drilled out, allowing you to dismantle the lock set and remove the cylinder. You can drill through a door lock quickly; it only requires a metal bit for your power drill.
Open the chuck on your power drill and insert your metal drill bit. Depending on the type of drill that you have the chuck may open by twisting the collar counterclockwise or you may need a chuck key to loosen it. Check your operator's manual to determine which method to use. Once the bit is inserted, tighten the chuck to hold it in place.
Switch your drill to the forward and fast setting. You will need a high speed revolution to drive the metal bit into the metal of the door lock. Be aware that battery-operated drills that are 14 volts or less will have a great deal of difficulty in doing this task. Ideally you should use a drill with a higher power rating to drill through a door lock.
Line up the drill bit in the key slot of the door lock. Engage the drill and press the bit into the lock until the bit has passed through the length of the lock. It is very important that you hold your drill level while you drill through the door lock, otherwise the bit will not evenly destroy the teeth on the interior of the cylinder that are holding the door in the locked position.
Reverse the direction of the drill and set it to "slow" and slowly pull the bit out from the lock while running the drill in reverse. When the drill bit is out of the lock, let the lock cool for at least five minutes before you continue to remove the lock.
Not all locks are drillable. Before you attempt to drill out your lock, go to your local hardware store and check the brand to make sure it is not marked "drill proof" or "pick proof." If it is, you will have to call a locksmith to remove the cylinder.
Don't rub your eyes after drilling metal; the small filings from the drilling can transfer from your fingers to your eyes and cause serious injury.