How to Fix a Broken Door Lock
Last updated: 30 September 2026
Check the key, lubricate the lock, tighten the fixings, or replace the lock if damaged.
Overview
A broken door lock is a security issue and can leave you locked out. This guide covers diagnosing and repairing common lock problems.
Step-by-Step Fix
Before beginning any repair, ensure you have isolated power or water supplies. Clear your workspace, gather standard hand tools, and wear appropriate personal protective equipment (PPE).
- First identify the problem. Is the key not turning is the lock stiff or is the cylinder loose. Each problem has a different fix. Try the key in the lock and observe what happens. If the key will not go in the keyhole may be blocked.
- If the key will not turn apply graphite powder into the keyhole. Insert the key and turn it gently back and forth several times. Graphite is a dry lubricant that will not attract dirt. Do not use oil based lubricants as they can gum up the lock over time.
- If the lock is stiff remove the key and inspect it for damage. A worn key is a common cause of lock problems. Compare the key to a spare if you have one. If the key is worn get a new one cut by a locksmith.
- If the lock cylinder is loose tighten the retaining screw. The screw is usually located on the faceplate of the lock or on the side of the door. Use a screwdriver to tighten it. If the screw is stripped replace it with a slightly larger one.
- If the door lock is broken and cannot be repaired the lock cylinder must be replaced. Measure the lock cylinder dimensions including the length and the offset. Purchase a replacement cylinder of the same size.
- Remove the old cylinder by unscrewing the retaining screw and pulling the cylinder out. Insert the new cylinder and secure it with the retaining screw. Test the lock with the key to ensure it operates smoothly.
- If the entire lock mechanism is damaged the lock case may need to be replaced. This involves removing the door handle and the lock case. Install a new lock case of the same size and reattach the handle.
- After any repair test the lock thoroughly. Lock and unlock the door several times. Check that the lock engages smoothly and that the door opens and closes without difficulty.
- To prevent future lock problems lubricate the lock annually with graphite powder. Keep the key clean and free from dirt. Do not force the key if it feels stiff. Apply graphite powder immediately.
- If you are locked out or the lock is severely damaged call a qualified locksmith. Attempting to force a lock can damage the door and make the repair more expensive.
Common Symptoms & Diagnostic Resolutions
Review the common error codes and operating symptoms below to quickly identify the root cause of the fault before ordering replacement parts.
| Symptom / Code | Likely Root Cause | Recommended Resolution |
|---|---|---|
| Key will not turn | Lock dry worn key or misaligned door | Apply graphite powder to the keyhole. Check the door alignment. If the key is worn get a new one cut. |
| Lock is stiff | Lack of lubrication or internal wear | Apply graphite powder. Work the key back and forth. If the lock is still stiff replace the cylinder. |
| Key breaks in lock | Worn key or seized lock | Call a locksmith to remove the broken key. Replace the lock cylinder if needed. |
| Cylinder is loose | Loose or stripped retaining screw | Tighten the retaining screw. If stripped fill the hole with a wooden matchstick and reinsert the screw. |
Frequently Asked Questions
How do I fix a door lock that will not turn?
Apply graphite powder into the keyhole and work the key back and forth. If the key is worn get a new one cut. If the lock is stiff or damaged the cylinder may need replacing.
What lubricant should I use on a door lock?
Graphite powder is the best lubricant for door locks. It is a dry lubricant that will not attract dirt. Avoid oil based lubricants as they can gum up the lock over time.
Can I replace a door lock cylinder myself?
Yes replacing a lock cylinder is a straightforward DIY task. Measure the old cylinder remove it and install a new one of the same dimensions. Test the lock before closing the door.
When should I call a locksmith?
Call a locksmith if you are locked out if the key has broken in the lock or if the lock is severely damaged. Attempting to force a lock can damage the door.