Symptoms
- Key turns with noticeable resistance
- Deadbolt binds partway through turning
- Problem is worse in cold weather
Likely causes
- CommonDry or dirty lock cylinderLocks need periodic lubrication and can accumulate dust and grime over time.
- CommonMisaligned deadbolt not lining up with the strike plateIf the bolt has to force its way into a slightly misaligned hole, turning feels stiff.
- PossibleWorn or bent keyA key that's worn down or slightly bent won't turn the pins smoothly.
- PossibleFailing lock cylinder internalsPins or springs inside the lock can wear out over many years.
What to do
- Spray a dry graphite or PTFE lock lubricant into the keyhole, not oil-based products which attract grime.
- Insert and remove the key several times to work the lubricant through the pins.
- Check whether the deadbolt only binds when the door is closed, which points to strike plate misalignment rather than the lock itself.
- Try a spare or newer-cut key if available to rule out a worn key.
- Adjust the strike plate as needed if the bolt binds only when engaging the frame.
- If a lubricated lock with a good key still turns stiffly, the cylinder itself may need replacement.
Tools and parts
- Dry lock lubricant (graphite or PTFE)
Dry lock lubricantSearch: “graphite lock lubricant”
Replacement deadboltSearch: “deadbolt lock set”
When to call a pro
Call a locksmith if lubrication and strike plate adjustment don't help, or if you suspect the cylinder itself is worn out.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.