Test a new key copy on the lock it is meant for while you still hold the original, because the original is your only known-good reference. If the copy fails later, after the original is in a drawer or with someone else, you lose your fallback and your comparison point. There is then no easy way to tell whether the copy, the lock, or the door is at fault.
The original key is your control
Until a copy has turned the lock smoothly, the original key is the only key you know works. That makes it your way in if the copy fails. It is also the yardstick you hold the copy against, and that second job is easy to overlook.
A lock that is wearing, or a door that has sagged slightly on its hinges, can make any key feel rough. With both keys in hand, you can try them on the same lock a minute apart and see which one behaves differently. Once the original is put away, a stubborn copy only tells you the door won't open. It doesn't tell you why.
How to test a new key copy on the actual lock
Test the copy on the lock it is meant for, not a similar one. Run the original through the same steps right before or after, and pay attention to feel. A difference you notice now is a clue. A difference you shrug off becomes a mystery later.
- Insert the copy slowly. It should slide all the way in with the same light resistance as the original, without catching partway.
- Check that the key seats. The shoulder, the small step where the blade meets the head, should stop against the face of the lock at the same depth the original does.
- Turn the key with the door open. Watch the bolt or latch travel fully out and fully back. A key that turns but leaves the bolt short has not done its job.
- Repeat with the door closed. A closed door puts pressure on the bolt, so this is where a marginal copy or a misaligned door tends to show itself.
- Remove the key in both the locked and unlocked positions. It should come out as easily as the original, with no wiggling.
- Run the whole sequence a few times, not once.
Is the problem the copy, the lock, or the door?
A copy that matches the original at each step, with no extra effort, has passed. That is the point where the original can go back on its hook.
A copy that turns only after jiggling or pushing harder than the original points to the copy. The cuts along a key's blade lift small spring-loaded pins inside the lock to set heights. When one cut is a little off, a pin sits slightly wrong and the key binds until you coax it.
A copy that turns partway, or won't turn at all, while the original turns cleanly in the same lock is a failed copy. The lock is answering correctly to the right key.
If the original also drags, the copy is probably not the culprit. The same goes for both keys turning easily with the door open but stiffly with it closed. Worn lock parts, or a bolt that no longer lines up with the strike (the metal plate the bolt slides into), affect any key you put in. The original is what lets you tell these cases apart.
A copy that works with effort has not passed
Opening the door once proves very little. A key copy that needs force rubs harder against the parts inside the lock, and that kind of key tends to get worse with use. It can stick or refuse to turn on a day when you are in a hurry and the original is somewhere else.
During the test, never force the key. If the copy stops, back it out gently and try the original instead. Twisting hard on a binding key can bend the blade or snap it off inside the lock, which turns a small problem into a lockout.
If the copy doesn't pass
Keep the original out and in use. Stop relying on the copy for anything that matters, and don't hand it to anyone as their only key.
Write a short note while the test is fresh: which lock, door open or closed, and what you felt at which step. Whoever looks at the problem next will want three things together: the original, the copy, and that note. If the note says the original drags too, the lock or door hardware may need a look rather than the key.
Upper East Locksmith works on key cutting and duplication, lock replacement and rekeying, and door hardware repair. To talk through what you found, call Upper East Locksmith at (347) 444-9725.
Frequently asked questions
Should I test a copy on every lock it is meant for?
Yes. Test a new key copy on each lock it is supposed to open, even when those locks share one key. Locks that take the same key can still wear differently, so a copy that turns cleanly in a front door can bind in a back door or a storage lock. Test each one while the original is still with you.
Is a copy that works only after a little jiggling good enough?
No. A key copy that needs jiggling works only for someone who knows the trick. Whoever else carries that copy has to discover the right wiggle at the door, and may not manage it. If the original turns cleanly in the same lock, treat the jiggling copy as one that did not pass and keep using the original.
What should I keep after a key copy fails the test?
Keep the failed key copy exactly as it is, without filing, bending, or marking the blade, because its shape shows where it differs from the original. Keep the original with it, along with a note naming the lock and what happened. If the copy was cut alongside others, keep those together too, since they may share the same fault.