The locking mechanism inside the doorknob of a house door is prone to failure due to the constant insertion and removal of the occupant’s house key. You can fix the locking mechanism inside of a doorknob that has jammed due to a house key having broken off inside of it. You will need to prepare a hardware tool and have some supplies from a hardware store to fix the lock so that it will once again work as it should. No locksmithing abilities are required.
Buy a hobby-style hacksaw blade from a hardware store, building supply store or hobby shop. Put on the work gloves. Put on the protective eye gear.
Turn on the grinding wheel. Place one side at the opposite end of the hacksaw blade that you are holding in your hands against the grinding wheel for 10 seconds. Rotate the hacksaw blade so that the other side is now against the grinding wheel.
Repeat this procedure every 10 seconds until you have a harpoon-like point at the end of the hacksaw blade. Remove the hacksaw blade from the grinding wheel. Turn off the grinding wheel. Remove the protective eye gear.
Hold the hacksaw blade with the teeth pointing down. Insert the harpoon-like end of the hacksaw blade into the doorknob’s locking mechanism so the teeth of the hacksaw blade are above the nubs cut into the key.
Press down on the hacksaw blade to engage the teeth against the key nubs. Pull back on the hacksaw blade to catch the front of the key against the harpoon-like end of the hacksaw blade. Continue pulling to force the broken key out of the lock.
Put the hacksaw blade away. Dispose of the broken key. Remove the work gloves.
Smooth the replacment house key’s tip gently to remove burrs with the nail file.
Apply powdered graphite to the replacment house key. Insert and remove the replacment house key from the locking mechanism of the doorknob a total of 10 times.
Wipe off the replacement house key with the paper towel. Wipe off the front of the doorknob with the paper towel. Throw the paper towel in the trash.