A key milling machine is a machine that cuts keys with a rotating cutter, copying a sample key or working from its code. It differs from a simple machine for flat cut keys in that it handles more complex profiles, such as the dimples and grooves of security keys.
The most modern ones are electronic: they read or receive the key code and cut the key without needing an original. Security cylinder manufacturers usually control who can cut their keys, which is why many copies can only be made with a key card.
We do not cut copies of keys. If you need to control who has a key to your home, the answer lies in the cylinder: a model with a protected key, or a change of cylinder when you do not know how many copies there are. See cylinder replacement.