Key Cutting and Key Control
Blanks, keyways, depth and space charts, the machines that cut them, and why restricted keyways are the only thing that actually stops a key being copied.
Blanks and Keyways
Before a key can be cut it has to be the right blank. Get the blank wrong and no amount of accurate cutting produces a working key. Blank identification is the first skill a new locksmith is taught and the one that separates a five minute counter job from a twenty minute one.
- A keyway filters which blade can enter. It is not a security feature by itself.
- Profile, blade length and shoulder position all have to match before cutting.
- Tip referenced keys cut from the shoulder will enter and never turn.
- Soft or loosely milled cheap blanks cause a large share of key does not work calls.
What a keyway is
A keyway is the shaped slot in the front of a lock cylinder. Milled grooves run along the length of the key blade and the plug is broached with the matching profile, so only a blade with the right cross section will enter far enough to reach the pins.
That is a mechanical filter, not a security feature in itself. Two keys with identical cuts on different keyways will not interchange, but a keyway is only as exclusive as the availability of its blanks. A Kwikset KW1 is one of the most common keyways in North America and blanks cost cents.
Identify a keyway by looking down the blade end on. The pattern of grooves, whether the milling is symmetrical, and where the widest groove sits are all diagnostic. A blank catalogue and a keyway gauge shorten the learning curve enormously.
Reading a blank
Blanks carry a manufacturer reference stamped on the bow, such as KW1, SC1, WR5 or Y1. Aftermarket makers use their own numbering that cross references to the original, which is why a cross reference chart lives beside every key machine in the trade.
Check three things before cutting. The keyway profile must match, the blade length must match, and the shoulder must be in the right place, because the shoulder is the reference point the machine measures every cut from. A blank with the correct profile and the wrong shoulder position produces a key with every cut in the wrong place.
Some keys reference from the tip rather than the shoulder. Ford and many automotive keys do. Cutting a tip referenced key from the shoulder gives a key that is close enough to enter and never close enough to turn.
Brass, nickel silver and the cheap blank problem
Brass is soft, cuts cleanly and wears fast. Nickel silver is harder, holds an edge longer and is what better blanks and most original equipment keys are made from. Steel blanks appear on some automotive and high security keys and need carbide cutters.
Very cheap imported blanks are the source of a large share of key does not work complaints. The alloy is soft, the milling tolerance is loose, and the blade often sits a fraction of a millimetre off in the keyway, which is enough to shift every cut relative to the pins.
Buy blanks from a real supplier and keep the cheap ones out of the shop. A key that fails a week later costs far more in trust and return visits than the few cents saved on the blank.
Machines and Accuracy
There are two families of key machine and they solve different problems. A duplicator copies an existing key. A code machine cuts to a specification. Both need calibrating, and an uncalibrated machine produces keys that work today and stop working in a month.
- A duplicator copies wear. A code machine cuts to the manufacturer's specification.
- Deburr every key. A ragged edge shaves brass into the cylinder.
- Cut and measure a known test key daily. Drift is invisible until keys start failing.
- A dull cutter rounds the bottom of a cut and sits the pin high.
Duplicators
A duplicator holds the original and the blank in paired vices. A stylus traces the original while a cutting wheel mirrors the movement onto the blank. Speed is the whole advantage. Ten seconds and no information about the lock is needed.
Accuracy depends on the stylus and cutter being exactly aligned and exactly the same diameter. That alignment drifts as the cutter wears, so a duplicator needs checking regularly against a calibration key and adjusting when it drifts.
Deburr every key. A cut leaves a sharp ragged edge that will drag on the pins, shave brass into the cylinder and give a key that feels rough and works badly. A wire wheel pass takes two seconds and is the difference between a good key and an acceptable one.
Code machines
A code machine cuts to a depth and space specification rather than to a physical original. You enter or dial in the code, the machine positions the blank precisely at each space, and the cutter descends to a defined depth.
Because it works to the manufacturer's own chart, a code cut key is a factory specification key. It works in every cylinder on the system rather than just the one worn cylinder it was copied from, and it can be produced with no original key present at all.
Modern computerised machines hold thousands of depth and space charts and can cut laser track automotive keys, dimple keys and tubular keys as well as flat steel. They are the largest single equipment investment a new locksmith makes and the one that most expands what jobs can be accepted.
Calibration and quality control
Cut a test key on a known code at the start of a working day and measure it. A micrometer or a depth gauge tells you in thirty seconds whether the machine has drifted. Doing this daily is the difference between one bad key and a month of them.
Watch the cutter. A dull wheel tears rather than cuts, leaving a rounded cut bottom that sits the pin slightly high. That produces the classic works in one lock but not another symptom on a keyed alike system.
Keep a record for master key systems. When a customer reports a key failure and you know the machine was in calibration on that day, you can look at the lock rather than at your own work.
Key Control
Key control is the answer to a question customers rarely ask and always need. Who can get a copy of this key made. On an ordinary keyway the answer is anybody with five dollars and a hardware store. For a building, a rental portfolio or a business that is a real problem.
- Do not duplicate has no legal force and creates only hesitation.
- Real control comes from a restricted supply chain plus an active patent on the profile.
- Ask when the patent expires before promising a customer long term control.
- Without an issue log and a signature list, a restricted system decays into an ordinary one.
Do not duplicate is not key control
Stamping do not duplicate on a key has no legal force in most jurisdictions and no practical force anywhere. The blank is still freely available, the machine still cuts it, and plenty of counters will copy it without a second glance.
It does a small amount of good by creating hesitation, and that is the whole of what it does. Selling it to a customer as security is misleading them.
Say the truth. If a customer needs keys that cannot be copied, they need a restricted keyway, and that is a different product at a different price.
Restricted and patented keyways
A restricted keyway uses a blade profile that is only sold to authorised dealers, usually under a contract that says where and to whom keys may be cut. A patented keyway goes further, because the profile itself is covered by an active patent and manufacturing an unauthorised blank is an infringement.
That is the real mechanism. Not a marking on a key but a supply chain that a hardware store cannot join and a patent that makes unauthorised copies unlawful to produce.
Patents expire, and when they do the blanks become generally available. Ask what the patent expiry is before recommending a system to a customer who expects twenty years of control.
Running a key control programme
The hardware is only half of it. The other half is administration. An authorised signature list says who may request a key. A key issue log says who holds which key and when it was signed for. A return procedure says what happens when somebody leaves.
Without the paperwork a restricted system decays into an ordinary one within two years, because keys accumulate in drawers and nobody knows how many exist.
Sell the programme, not just the cylinders. Annual audits, a documented key list, a defined turnaround for new keys, and a rekeying allowance when control is lost. That is a service contract, it is recurring revenue, and it delivers something the customer cannot get from a box of locks.
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