Why is my deadbolt suddenly hard to turn with the key?
A deadbolt that suddenly gets stiff is almost always one of two things: the bolt is binding against the strike plate because the door or frame has shifted, or the cylinder inside the lock has gone dry, dirty or worn and the pins are no longer lifting smoothly. A worn or freshly copied key is the third common culprit, and it often shows up right after someone has a spare cut.
The quick way to tell them apart is to open the door and turn the key with the bolt throwing into open air. If it turns easily that way and only fights you when the door is shut, the lock is fine and the alignment is the problem. If it is stiff either way, the issue is inside the cylinder or in the key itself.
Why it happens
Doors move. Wood swells and shrinks with humidity, hinges loosen, and houses settle a little every year, so a bolt that used to slide into the center of the strike hole starts dragging on the edge of it. You feel that drag through the key as resistance, because the key is doing the work of forcing the bolt past the obstruction.
Inside the lock, the cylinder is a stack of small spring-loaded pins. Dust, grit, old grease and corrosion all slow those pins down, and exterior locks catch the worst of it — wind-blown dirt, rain, and salt air near the coast, which corrodes internal parts and the bolt itself. Oil-based lubricants make it worse over time: they attract dust and turn to a sticky film that holds the pins down.
Keys wear too. A key is a thin piece of soft metal that gets filed down a little with every use, and a copy cut from an already worn copy drifts further from the original. Eventually the cuts are shallow enough that the pins sit at the wrong height and the key has to be jiggled or forced — which is usually when it finally snaps off in the lock.
What you can check yourself
Swing the door wide and turn the key to throw and retract the bolt. Smooth with the door open but stiff when closed means alignment, not the lock.
Check the metal plate on the jamb for shiny scrape marks or a bolt hole that no longer lines up with the bolt. Those marks show you exactly where the bolt is rubbing.
If you have an older or original key, try it. If that one turns easily, your everyday key is worn and needs to be recut from the original, not from the worn copy.
Snug up the hinge screws and the two screws holding the lock halves together. A sagging door or a lock pulled slightly out of square binds the bolt.
A dry graphite or PTFE lock lubricant is made for cylinders; household oil and penetrating spray gum them up. Work the key in and out a few times after applying.
When to call a pro
Call someone if the key has to be forced, if it has already broken off, if the bolt will not fully extend, or if lubricant and tightened screws made no difference. Forcing a stiff cylinder is how a key snaps inside it, and a strike plate that needs to be moved or a mortise that needs to be deepened is chisel-and-alignment work that is easy to do badly on an exterior door.
Also worth a call if the lock is corroded, if the door is a security entry you depend on, or if you have just moved in and do not know how many copies of the key exist — rekeying is usually faster and cheaper than replacing hardware. When you are ready, call USA Home Repairs and we match you with a vetted local pro near you — free estimate, and you approve the price before anything starts. (888) 996-7488.
What a pro will do
- Diagnose bolt versus cylinder
The pro separates an alignment problem from a lock problem before touching anything, so you are not paying to replace a deadbolt that works fine.
- Realign the door and strike
That can mean resetting hinge screws, repositioning or re-mortising the strike plate, or adjusting the bolt hole so the bolt lands clean.
- Service or rekey the cylinder
Cleaning, repinning and rekeying brings a sticky cylinder back and retires every old key at the same time — useful in a home you have just bought.
- Replace worn or corroded hardware
When a deadbolt is past service, a pro fits new hardware, including high-security or smart locks, and can key it to match your existing doors.
- Extract a broken key
If a key has snapped off in the cylinder, a pro removes the fragment and cuts fresh keys rather than leaving you with a lock that has to be drilled.
Related questions
Can I just spray WD-40 into the lock?
It will loosen things for a few days, then attract dust and leave a sticky residue that makes the cylinder worse. A dry graphite or PTFE lock lubricant is the right product for pin tumbler cylinders.
Why does my deadbolt only stick in certain weather?
Wood doors and frames swell in humidity and shrink when it is dry, so the bolt lines up in one season and binds in another. If it only sticks a few weeks a year, alignment is marginal and a small strike plate adjustment usually fixes it for good.
Should I rekey or replace the deadbolt?
If the hardware is solid and only the keys are a concern, rekeying the existing cylinder is the simpler route. Replace when the lock is corroded, physically worn, or you want a different grade or a smart lock.
I just moved in — how do I know who has keys?
You cannot know, which is why rekeying every exterior lock is the standard first step after closing. A pro can rekey several doors to one new key in a single visit.
How do I avoid a locksmith bait price?
Get the price before the work starts rather than after the lock is drilled. Call USA Home Repairs at (888) 996-7488 and we match you with a vetted local pro near you — free estimate, and you approve the price first.
Want a pro to look at it?
Leave your number and we call you right back to set a time. Every visit is a free estimate, with no obligation, and we'll match you with a vetted local pro near you.
Rather talk to someone? Call (888) 996-7488.