For key duplication, bring the key that is least worn and closest to the original cut. Usually that is the original key or the first key supplied with the lock. A heavily used original can still be a worse source than a lightly used copy. A duplicate follows the shape of the key it is cut from, so any wear or cutting error in that key carries into the new one.
Why the source key sets the limit for the copy
A key works because of its cuts, the notches along the blade. Inside the lock cylinder, small spring-loaded pins rest on those cuts. When each cut lifts its pin to the right height, the cylinder can turn. A duplicate is made by following the cuts of the key you hand over, so the new key can only be as close to the lock's design as its source was.
The original key: fewer inherited errors, but not immune to wear
An original key, or the first key that came with the lock, was cut to the lock's intended pattern. A copy made from an original starts with no errors passed down from earlier copies. The only flaw it can inherit is whatever wear the original has picked up.
That wear matters. An original that has gone in and out of the lock every day for years has rounded cut edges and a smoothed tip from metal rubbing on metal. Hold it next to another key for the same lock. If the peaks between cuts look softer, or the top edge of the blade shines from use, that original has done a lot of work. A spare original that sat in a drawer is often the cleaner source, even though both carry the same label.
An older copy: how small errors add up
A copy rarely matches its source exactly, even when it is cut carefully. Cut a new key from that copy, and the small difference gets copied along with a little more. Call it copy-of-a-copy drift. Each generation moves a step further from the original pattern, and the steps add up. Daily use wears the copy on top of that, so an older key of unknown history can be several steps away from the lock's design.
An older copy is still a fair source when it slides in and turns the lock smoothly and looks like the other keys. It is a weak source when you have to jiggle it or pull it out slightly before the lock gives. Watch for visible differences too. Cuts can look shallower or uneven next to another key. The bow, the part you hold, can carry a different stamp from the rest, which hints that the key came from another round of copying.
Which key should you bring?
- Gather every key you have for that lock and lay them side by side. Note which look like the original and which look like later copies.
- Try each one in the lock. The key that goes in and turns without coaxing is your lead candidate.
- If two keys work equally well, pick the one with crisper cuts or the one that appears to be the original.
- Check the bow and blade for stamps such as do not duplicate or a restricted key number. Restricted and high-security keys are often handled differently from standard keys, so mention any marking when you make the request.
- If every key needs jiggling, skip the copy. A duplicate starts out no better than its source. Ask about rekeying, which changes the pins in the cylinder so a new key works and the old ones stop working, or about replacing the lock.
What to hand over with your request
Bring more than one key. The backup matters if your first choice turns out to be a weaker source than it looked.
- The key you picked as your source
- Your second-choice key for the same lock, as a backup
- A note saying which lock it opens, such as the front door deadbolt or a storefront door
- The number of copies you need
For a restricted or high-security key, or if rekeying is on the table, details about the lock help: which door it is on and a photo of the lock face. Upper East Locksmith offers key cutting and duplication on the Upper East Side and in nearby neighborhoods such as Yorkville and Lenox Hill, and also handles rekeying and restricted keys. To talk through which key to bring, call Upper East Locksmith at (347) 444-9725.
Frequently asked questions
Should I bring all my keys for a lock, or just one?
Two keys for the same lock are usually enough for duplication: the one that turns most smoothly and a second choice as a backup. If you cannot tell which is better, bring all the keys for that lock after testing them at the door. Keys for other locks only need to come along if you want copies of those too. Label each one so nothing gets mixed up.
Does the number of copies I need change which key I should bring?
The number of copies does not change which key makes the cleanest source, but it raises the stakes. Each copy inherits the same starting point, so a worn source passes its errors to several keys at once. When you need multiple copies, have them all cut from the cleanest key. Making one copy and then copying that copy adds drift.
What if my only key is one I have never tested in the lock?
Try an untested key in its lock before using it as a source for duplication. A key from a move-in envelope or a drawer can belong to a different lock, or it can be a worn copy that barely turns. If it slides in and turns smoothly, it is a reasonable source. If it struggles, a copy made from it will carry the same problem.
Is it worth rekeying instead of copying when I am not sure where all the older keys are?
Rekeying is worth considering when older keys are unaccounted for, because copying adds keys without retiring any. Rekeying changes the pins inside the lock cylinder so a newly cut key operates the lock and the old keys no longer do. It also gives you a fresh source key, which avoids the drift that builds up from copying old copies.