Remove the two screws on the back of the thumb latch with a Philips head screwdriver. Remove the thumb latch to expose its mounting plate. The two screws on the mounting plate hold the lock together. These only need to be hand-tight. It they are over tight, they can make the deadbolt difficult to turn. Loosen the screws about half a turn each. Replace the thumb latch. If the bolt still does not turn easily, proceed to Step 2.
Insert the narrow nozzle on a can of Teflon lubricating spray into the key slot on the cylinder a quick spray. The Family Handyman recommends Teflon spray over traditional graphite as it leaves behind a dry powdery residue that keeps locks lubricated longer.
Turn the thumb latch on the back of the door a couple of times and insert and turn the key to operate the deadbolt. If it still does not turn easily, move to Step 3.
Remove the thumb latch as in Step 1. Remove the screws on the mounting plate and the cylinder and its collar on the front should come off as well. Set the screws, plates and the cylinder aside.
Spray the Teflon lubricant into the sliding mechanism that operates the deadbolt. It is long and thin with several small holes along its length. Cover it completely with the spray and let it set for a few minutes.
Insert a screwdriver into the center hole in the mechanism and turn it to activate the deadbolt. When it moves freely, reassemble in the reverse order as you took it apart.
Close the door and operate the deadbolt again. If it does not operate freely when closed, you have a problem with the alignment of the strike plate on the doorjamb.
Open the door and examine the strike plate for signs of wear -- marks where it may be making contact with the bolt. This is often at the top or bottom edge of the bolt hole. If it appears to be only a little out of alignment, file down the edge of the hole or the edge of the bolt with a metal file until the bolt operates smoothly.
Things You Will Need
- Teflon spray
- Phillips screwdriver
- Metal file
- Ensure all door hinges are tight before beginning lock repairs. A sagging door can misalign locking mechanisms.
- Spray in a lock de-icer when temperatures are very cold and the key won't turn in the lock.
- On some single-cylinder deadbolts, the screws that go through the thumb latch are the screws that hold the lock together and there is no mounting plate beneath.