Lock lubricants, what helps and what hurts

A lock is a small machine with metal parts that slide against one another. A pin tumbler cylinder has a row of tiny pins and springs, a plug that rotates, and a cam or tailpiece that moves the bolt. Every time you turn the key those parts rub, and a thin film of lubricant keeps the rubbing smooth and slows wear.

Factory lubricant does not last forever. It dries, it collects dust, and it migrates away from the points that need it. In a dry, hot place the film can turn to a sticky varnish. In a wet, cold place it can wash out, or it can thicken until the bolt moves reluctantly.

So the question is not whether to lubricate but with what and how much. A small amount of the right product every season or two keeps most locks healthy. A large amount of the wrong product can turn a minor stiffness into a lockout, and that is why the choice matters. Many service calls for stuck locks begin with a well meant can of spray that was used years earlier and slowly turned the inside of the cylinder into paste.

For the keyway and the pins, dry lubricants are generally the safest choice. Powdered graphite is the classic example. It is a fine, slippery powder that coats the pins and the plug without becoming sticky, and it does not attract dust the way an oil does. A small puff into the keyway, followed by working the key in and out, is usually enough.

Another dry option is a spray made for locks that carries PTFE or silicone in a carrier that dries off. The carrier evaporates and leaves a very thin slippery film. These products are made to stay clean in the cold and do not gum up dust. As with graphite, a short burst is plenty.

Dry lubricants have a few cautions. Graphite is black and can stain keys, hands and light colored doors, so apply it carefully. It also can clump when it meets moisture, so it works better in a lock that is not already wet. Always read the label, and choose a product that says it is made for locks and keyways. If the label talks about cleaning, degreasing or loosening rust, it is probably not what you want in a cylinder. If it mentions locks, cylinders or keyways, that is a better sign. When in doubt, a smaller amount of a simple product beats a larger amount of something unfamiliar.

Many households keep a general purpose penetrating spray or a light household oil. These products are useful for rusted bolts and squeaky hinges, but they are not ideal inside a cylinder. They are wet, they stay wet, and a wet film collects lint, dust and fine metal shavings. Over months, the cylinder fills with a gritty paste that makes the key drag.

Some penetrating sprays also contain solvents that dissolve the factory grease and leave the parts dry. A lock sprayed once may feel wonderful for a week and then become worse than before. Cooking spray, candle wax and hand lotion are worse still, because they gum up and attract dirt. Bar soap rubbed on a key is an old folk remedy that leaves a waxy residue, and pencil lead is only a rough stand in for real graphite powder.

Thick grease belongs on gears and sliding parts that can be reached, not in a keyway. It cannot flow into the narrow spaces between pins, and in cold weather it turns stiff. If you inherit a lock that was packed with grease, it usually needs to be cleaned out and relubricated with a light dry product, or replaced. Grease can also mix with graphite to form a thick black paste, so avoid combining products. Choose one approach, clean off the old, and then stay with the new.

• Use dry lubricants for the keyway and the pins.
• Keep general purpose oils away from the inside of a cylinder.
• Avoid cooking spray, wax, soap and hand lotion.
• Do not pack a keyway with thick grease.
• Wipe the key clean before you use it again.

Not every part of a door lock is a cylinder. The latch bolt, the deadbolt itself, the hinge pins and the strike plate are all open to the air, and these exposed metal parts often benefit from a light oil or a silicone spray. A tiny drop on the edge of the latch, worked in by moving the knob, reduces friction.

The key idea is that the product should reach the moving surface and stay there, without dripping or leaving a wet residue. A lithium or silicone based grease applied sparingly to a deadbolt can protect it from corrosion in damp conditions. Wipe away the excess so it does not smear onto clothing or collect dust.

Hinges are often the hidden cause of a sticking door. Pin hinges on older doors can be oiled without taking the door off, one hinge at a time, while a helper supports the door. A squeaking hinge is dry. A light oil on the hinge pin, applied while the door is open, removes the squeak and lets the door swing evenly. Keep this separate from the cylinder and the keyway, and you will have a better result. One trick is to put a tiny amount on a cotton swab and touch it to the latch edge, rather than spraying toward the door, so none of it drips onto the finish or into the keyway below. For the connection between hinge wear and latching trouble, see doors that do not latch, alignment basics.

Padlocks live outdoors and take a beating. Rain, dust, pollen and frost enter through the keyway and the shackle holes. A padlock on a farm gate, a boat trailer or a shop door can seize if it is neglected, and then the key will not turn when you need it.

For outdoor padlocks, a dry lubricant in the keyway and a light oil or silicone on the shackle works well. Work the shackle in and out a few times to spread the lubricant. Look for a model with a cover over the keyway if the padlock is exposed to the weather, and clean any grit from the shackle holes with a small brush. After a winter, check whether the padlock still locks firmly. A shackle that no longer clicks into place is a sign of dirt or wear, and a padlock that does not lock firmly does not protect what it is attached to.

Gate hardware needs attention too. Hasps, latches and chains rust, and rust ruins moving parts. A light coat of oil, wiped off, protects them. Our notes on gates and padlocks on rural property and storage unit and shop padlocks cover choosing hardware that stands up to the weather.

The North State asks a lot of lubricants. Valley summers bring long stretches of dry heat that bake oil into varnish and fill keyways with fine dust. Mountain winters bring frost, snow and moisture that thicken grease and freeze water inside the lock.

In heat, favor dry lubricants that do not run, and clean dust from the keyway before you apply anything. In the cold, pick products made to stay fluid in low temperatures, and use less. A thick, sticky film is more harmful when the temperature drops, because the spring pressure that moves the pins is gentle. Each pin sits on a tiny spring, and a film that adds even a little drag can stop a pin from dropping back into place. That is why a lock can feel fine in the garage and refuse to behave outside.

If your deadbolt sticks only in the cold, lubrication is only part of the answer. Alignment and moisture are common causes as well, as you can read in a deadbolt that sticks only in the cold. For the hot end of the year, why locks stick in hot summer weather covers what heat does to doors and cylinders.

Start by cleaning. Wipe the face of the lock with a dry cloth and remove any visible dirt. If the keyway is gritty, a short blast of compressed air can clear loose dust, though you should avoid blowing dirt deeper into the lock.

Next, apply a small amount. For graphite, one gentle puff is enough. For a spray, aim it at the key and let a thin film coat the blade, then insert the key and work it in and out several times. Do not flood the lock. If you see liquid on the face of the lock after you apply it, you have used too much. More is not better, and extra product runs out of the keyway and collects grit.

Finally, wipe the key and the area around the keyway, and test the lock several times with the door open. Make sure the bolt moves freely and that the key comes out clean. If you notice dark smears, wipe them off before they stain clothing. A seasonal routine, once in spring and once in autumn, is plenty for most household locks. Pair it with a check of the screws on the strike plate and the hinges, since a lock can seem stiff when the real trouble is a door that has moved. Keep a note on the calendar so you do not have to rely on memory.

Lubricant cannot repair a worn or damaged lock. If a key turns hard even after cleaning and a light dry lubricant, the cause may be a worn key, a bent pin, a misaligned bolt or a faulty cylinder. Adding more product at that point only hides the symptom, and it can make the real repair harder, because a locksmith then has to clean out the extra product before testing the parts.

Watch for signs such as a key that must be jiggled, a plug that feels gritty, a cylinder that turns only partway or a latch that does not spring back. These often point to a mechanical issue, and a locksmith can examine the lock and tell you whether it can be cleaned, rebuilt or replaced.

A worn key is a frequent hidden culprit. A key that has lost its sharp edges rides the pins less accurately. Read what happens when a key wears down and why duplicate keys sometimes fail before you spend time on lubrication. A fresh key cut from a good original can fix what spray cannot.

Electronic and keypad locks have motors, gears and circuits, and many manufacturers advise against lubricating the electronics at all. The mechanical key cylinder on such a lock can be treated like any other, but never spray anything into the keypad or the battery compartment. Moisture and oil can creep onto the circuit board and the contacts, and the result is a lock that behaves erratically or stops responding. Check the instructions that came with the lock.

Car locks are a different environment. Door lock cylinders and ignition cylinders are small and exposed to dust and moisture, and the vehicle often has a transponder or an immobilizer that does not tolerate sprays. A light puff of dry lubricant in the door keyway is usually fine. Do not spray the ignition switch or any electronics.

If a car key sticks, it may be worn, or the lock may be dirty. In some cases the issue is in the steering column or the ignition, which needs a professional. See our automotive locksmith page and the guide to ignition trouble signs for guidance on what to check.

If you have tried a clean key, a light dry lubricant and a check of the door and the hinges, and the lock is still stiff, it is time to call a locksmith. A professional can take the cylinder apart, remove old lubricant and dirt, replace worn pins and springs, and reassemble it with the correct product.

Sometimes the sensible answer is a new cylinder or a new lock. If the lock is old, damaged or poor quality, repair may cost more than replacement. We can advise honestly on which makes sense, and we will say so if an old lock is simply worth keeping with a clean and a fresh key. Not every stiff lock needs new hardware. Our lock repair service covers cleaning, rebuilding and replacing, and we come to you in a branded van carrying professional tools and common hardware.

If you are unsure, describe the lock and what it does in the request form. The phone line is coming soon. A short description of the lock type, the weather and what you have already tried helps us decide what to bring.