Thread: U-Lock?
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Old 06-08-11, 10:41 AM
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That's true, but high carbide steels are good for chains ... if we made a U lock out of boron carbide, it'd crack from a bottle jack easy. Steel with that high carbide content is more brittle than regular steel. Soft mild steel will flex, stretch, and fatigue under stress before breaking.

You need a type of steel that flexes, but that is hard enough to resist flexing. If it's very hard, it'll resist a ton of force; but when you apply it, it'll shatter. If it's soft, you can bend it up until it breaks. If it's hard, but flexible, it'll bend and stretch under excessive force at its weakest points, requiring much more energy to defeat. It might take 0.95 tons instead of 1 ton, but it'll take 0.95 tons applied consistently, enough to force a permanent deformation, and over a longer reach. Further, the metal will be harder to force into fatigue, meaning you might completely mangle the lock without actually breaking it--if the clasp holds.

And, still, it has to resist cutting, sawing, refrigerants, impact, and compression attacks (bolt cutters). I'm not saying you can't take out boron carbide steel with a rotary tool and cutting disc; but you're going to need a stack of cutting discs and about 10-20 minutes depending on steel quality and thickness. Bolt cutters? Literally, you're talking about an explosion here, you're going to need 30,000 pounds of force.

This won't happen with steel useful for U-locks. They might resist bolt cutters, but not quite as well. They'll resist sawing, not quite as well as harder steel, but well enough. Cutting disc? Short work, the metal's going to peel off. Bottle jack? Hammers? Oh yeah, the steel actually flexes instead of shattering, so even if you overcome its strength, you've ... managed to dent it. Slightly. Good job. High-hardness carbide steel will likely just break the hammer, but shatter under bottle jack pressure.

It turns out you need different tools to crack different locks.
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