- 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 catalog 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 millimeter 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.
Common Questions
Why will the shop not cut a copy of my key?
If it is a restricted keyway, the blank is patented and only authorized dealers can buy it, usually against a signature. That is the whole point of the system and it is working as designed.
Are all house keys basically the same?
Most residential keys in the United States are cut on one of a small number of profiles. That is convenient and it is also why a stranger with the right blank can try.
What does DO NOT DUPLICATE stamped on a key mean?
Legally, very little. It is a request, not a restriction, and many counters will cut it anyway. A patented restricted keyway is the only version of that request that holds.
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