THEY DON"T PICK UP NON-MAGNETIC METALS.
Then they have a very serious problem with their detectors that runs well beyond knives.
The detectors used in airports and most other checkpoints are calibrated to allow some small amount of metal. Shoes have metal eyelets for the laces very often. Slacks may have a metal fastener. Jeans often have metal buttons and/or rivits. Belt buckles are usually metal. Suspenders have metal fittings. Wedding rings... after years, many people can't take them off if they want to. Many people wear earings and other minor jewlery that is time-consuming if not embarasing to remove. Many people have MINOR surgically-implanted metal inside their body (I'm not talking about big stuff, but just a single small screw to help set a broken arm, a stint in a blood vesel, etc.)
The newer detectors actually measure the concentration of metal, not the amount. A one-ounce lump of steel in your pocket may, for example, set the detector off. But two quarter-ounce cufflinks and a half-ounce belt buckle will not because the metal is spread out.
Modern metal detectors are not magnetometers. They do not detect the magnetic properties of the knife. They detect it's ability to conduct an electrical current.
All metals -- aluminum, titanium, Talonite, Stellite, you name it -- all metals create an electrical current when a magentic field moves through them. This is how most electrical generators work. Consider a classic river damn. Water flows through the damn and turns the turbines as it goes. The rotating turbines turn large magnets. Those spinning magnets create a moving magnetic field. That field moves through a coil of wire which is typically made of copper or aluminum (both non-magnetic metals). When that field moves through that coil of wire, it induces an electrical current in the wire. And that, my friends, is how we get electricity. (Notice that accounting irregularities are optional.)
As is very often the case in physics, the opposite is also true. When electricity flows through a metal wire -- again, any kind of wire magnetic or not -- it creates a magnetic field. This is how electric motors work. Electrical current flows through a coil of wire and generates a magnetic field. That field is opposed by a set of permanent magnets. As you know from experimenting with them, magents have two poles called North and South. The North pole of one magnet will attract the South pole of another. But, the North pole of one magnet will repel the North pole of another. The coil and the permanent magnets inside of a motor are mounted in such a way that when the current flows though the coil, the two North poles face each other and repel. And that, my friends, is what makes a motor turn.
So, how does a metal detector work?
Simple. It starts by creating a magnetic field. That magnetic field induces a current into any metal that you may be trying to carry through it. Next, the detector abruptly turns off that magnetic field. This causes the current flowing in the knife in your pocket to stop. But the current doesn't stop immediately. It's a bit like a car when you slam on the brakes. As anyone who's ever been responsible for a rear-end collision knows, there's a brief interval between when you press the breaks and when the car stops. Similarly, there is a brief interval when that current continues to flow. Electrical current flowing in a metal object causes a magnetic field around that object. Eureka! That's what the detector detects!
It doesn't matter if the metal is magnetic or not. If it's metal, the detector's magnetic pulse will induce a current in it. If it's metal, then when the pulse suddenly ends, there will be a slit-second in which that current continues to flow and creates a magnetic field of its own.
It works on copper. It works on brass. It works on aluminum. It works on Talonite. It works on any metal at all.
Practical, reliable, inexpensive detectors using this method have existed for about fifteen years. There is no excuse for still using magnetometers for security screening.
Between aluminum, brass, and titanium, I can easily make a very functional gun from non-magnetic metals. Only the spring needs to be steel... or I could substitute rubber. A rubber spring wouldn't be as durable, but maybe durability isn't high on my list of criteria for this particular gun.
So, if LAX is still using magnetometers, they've got a big problem.
