Master padlocks are made by using laminations of stamped steel plates. Most other padlocks have cast metal bodies. Are the Master-type locks stonger? It would seem that making a lock body from plates uld involve extra expense-is this justified?
This factually-oriented question might get better answers in GQ.
The laminate ones are very strong, speaking as one who enjoyed disassembling locks as a kid (and I just busted them open to see how they worked, not to do anything bad).
I believe the laminate plate locks are much cheaper to produce than quality bar stock locks and they are very close to the same effectiveness if not better.
Here’s an overview of several lock types I faced as a teenager with too much time on my hands:
[li]Master-style combination locks. Those are sheetmetal that has an edge rolled over the back, holding the back plate on. Very weak. I used to pry these apart with ease.[/li][li]Cheap brass padlocks. These are the key locks that have a brushed metal surface. The brass body of the lock is actually the lock cylinder, and the pins are inserted in holes that have been drilled through the side of the entire lock. The purpose of the brushed finish is to hide the little brass plugs that cover where the pins were inserted. Since brass is such a soft metal, these are very weak locks. A hammer will kill one of these in seconds.[/li][li]Cast metal locks. There are many that are made of a zinc or aluminum casting, or possibly one of steel for a better lock. There is usually still a seam that can be pried, and the sides are often a press fit, held together by rivets or pins. The metal is often fragile and will give way to a hammer quite easily.[/li][li]Good bar stock padlocks. These are made by manufacturers like American Lock. They are made out of a solid hunk of metal, and in contrast to the cheap brass padlocks, the cylinder is a separate component. The mechanism is quite strong and is often designed to be disassembled for service. These are strong, but expensive.[/li][li]And those plate locks you mentioned. Those are a cast-iron pain in the ass to bust open. The plates provide a great cumulative thickness of steel that is not easily breached. For much lower cost than bar-stock solid steel or brass (such as American) you can buy a laminated Master lock that will last forever and will be very difficult to destroy. BTW, the pins/rivets that hold the whole thing together are very hard, and even if you cut the mushroom part off, the expanded part continues inside the drilled holes, making it difficult to simply cut off the rivets to take apart the plates.[/li][/ul]