Aluminum body lock

[guest5999]

I picked up a cheap lock at my local hardware store awhile ago but it was rekeyable and had serrated pins. It's been great to practice on, but package markets the lock as "Maximum Security" but right next to that, it says, "Solid Aluminum."

Is it just me or are these two statements at odds with each other given how easy it is to cut/drill/grind aluminum?

[NickBristol]

Lock manufacturers are notoriously good at making their products sound like they impregnable but pretty much every post on this site proves their marketing is nothing but nice copy that convinces people that don't know better.

I guess the moral is never to believe what is says on the packet.

[guest5999]

That's kinda what I figured. Just wondering if there was anything I was overlooking that would make an aluminum body less trivial to cut through that I thought.

If I'm not mistaken, aluminum locks are used for safety lockouts on machinery and whatnot, but I highly doubt then that they're marketed as "maximum security" in that case.

[gstrendkill]

"cheap lock" and "maximum security " is completely contradicting when talking about the same lock

[Raymond]

There are several aluminum products that are extremely difficult to cut. They tend to bind in the teeth of whatever you are cutting them with and are a royal pain in the hasp. Unfortunately they melt much more easily. But, considering the ease by which a shackle can be cut, the body of the lock is very seldom attacked to open the lock. These locks are quite attractive when the cost and weight are significant factors.

[linty]

Aluminum isn't really much easier to drill than brass or zinc, probably a little harder because it's easy for a bit to jam. however it's definitely not something I'd brag about on the packaging for my locks.

[niksoft]

It could always be an aluminum alloy. While regular aluminum is fairly soft it's alloys are very commonly used in the aerospace industry because if their flexibility, durability and corrosive properties. Mostly mixed with copper, zinc, manganese, silicon, or magnesium; though sometimes with lithium and other, harder metals, the alloys have proven to be quite hard and light...

Here are some examples:
Al-Cu alloy (duralumin) - commonly used in moving aircraft parts and engines, depending on the tempering of the metal it can be harder or softer, but averages around 450MPa of yield strength. Mild steel in contrast, the steel that is commonly be used for casting, yields the strength around 500MPa
Al-Zn alloy (7075 namely 7075-T6) - another aircraft metal, yield strength 510-538MPa, tensile strength 434-476MPa.

So yes, an aluminum cast lock may be as hard to cut as a steel cast lock, it wouldn't be hardened steel equivalent by far (those go up and over 1000MPa) but it will surely not be any less secure then a typical steel lock.

Besides, why are you worrying that someone will saw/drill through your lock? sawing is how really really stupid criminals think of opening locks, most pin tumbler locks are either cut at the shackle using a big pair of wire cutters, beat the lock off with a hammer (that makes lots of noise though) or using a wrench and a hardened blank key, they simply make a new sheer line, so getting your lock drilled through, is the least of things to think about in security terms here. Oh a really intelligent thief could use a bump key too i guess...

[niksoft]

correction to the above post, i meant ofcourse that most pin tumbler padlocks would probably be opened using those methods... another method may be a shim...

[raimundo]

as I started to read the thread, I was going to post certain things, but lately when I seen Raymond posting hes got to the very things I was going to post first... uncanny,

aluminium will fill the teeth of a file and coat the abrasive surface of a grinding tool. it will give slowly under a pinch cutter but it will not fracture through and as the cutter gets in deeper, the resistance increases.

A propane torch will make aluminum into droplets like silver wrapped hershey kisses. the melting point is about 1100 fahrenheit.

american lock company makes a lot of nice colored anodized aluminum locks. this could be good if weight is an issue, such as on aircraft where keeping weight down counts.

In some ways, aluminum locks can be high security, but the form of attack is the issue. with a flame attack, a steel body lock is secure against a propane torch, but not a propaneoxygen flame. flame will bypass most metal locks. chubb may have some flame resistant ceramic locks.

[niksoft]

not doing this to be the devil's advocate, i just wanted to see if the melting approach is actually worth pursuing, simply hypothetically.

For this simply hypothetical journey, i am going to use one of Aluminum alloys that has the higher melting point, and is not as rare as one may think, and if i was making an aluminum lock, this would be the alloy of choice for me. Anyhow, there is a family of alloys that employ arsenide, the alluminum arsenide bond (such as one used in aluminum gallium arsenide) weilds the highest melting temperature in aluminum alloys 1740C +-20C which is about 2013K or 3164F, from now on i will also refer to the metal using it's chemical composition AlAs

So what else do we need to know for further calculations.... Specific heat (or amount of energy needed to raise 1g of a material 1degree Celcius) of AlAs above 300K is calculated using this formula 0.476+6.2*(10^-5)*T-6.5*(10^3)(T^-2) and is measured in J/g K

Also if you are melting something then aside from specific heat you also need to know the heat of fusion or amount of energy needed to chage 1g of the material from solid to liquid form (temperature change=0). This one is harder to get, most metallurgy papers are not free, so i had to guesstimate, Aluminum being the main element was the starting point of 94.5cal/g so just for roundness and actually moving in an opposite direction of where the real specific heat of AlAs would be, i will use 90J/g.

One other thing is how much aluminum is used in the lock, and to compensate for my rather low heat of fusion figure i will use a lock weighing 1kg or 1000g (2.2lb).

And lastly, i have written the calculation for specific heat, now i will make it into a number, because i don't want to unnecessarily use complex calculations, especially if i guesstimated on a few things... taking the middle of the line temperature i will also define the specific heat of AlAs, at 1156K (you can plug it into the formula above) the specific heat of AlAs is at 0.545cal/g

Now the fun part:
Ht - total heat energy needed
Hf - total heat of fusion needed
Hs - total specific heat needed
Ht=Hs+Hf
H=mcΔT
Hf=1000g*90cal/g*(0K)=90,000cal
rememger in transition from solid to liquid no temperature is gained/lost

lets take that it's 40C outside (really hot)

Hs=.454cal/g*1000g*(1740C-40C)=771,600cal

Ht=861,800cal or 3,605,771J

Now to the propane torch, from what i have been able to find, the standard output is about 55,000J/g, a normal burner contains about 400g of propane leading to the total possible output of about 22,000,000J

let's give our heating a really good efficiency, something like 60%, then the total heat needed to melt 1kg of AlAs is about 5,050,000J. Doing the math, it will require you to burn 23% of the tank or about 80-90g of propane.... you go figure how long it will take...

All i'm saying is that melting the lock may not be the fastest or easiest way to open it...

P.S. once again the figures are really vague, so vague i would not consider this very scientific, but it took a long time to research this much, so...

[maintenanceguy]

Aluminum is easier to cut or drill than steel but steel's not really that hard to breach. Most padlocks use a harder steel on the shackle but not on the body of the lock.

I don't think the level of security is all that different between the two. With a drill and regular old drill bit you might drill through an aluminum lock body in 6 or 7 seconds and it might take you 10 seconds if it were steel.

As far as melting aluminum, I can cut through steel with a cutting torch in seconds. Aluminum won't cut with a cutting torch very well, it just sort of softens until big chunks fall out and you don't really have much control on what chunks fall out. I can cut a threaded steel coupling off of a piece of pipe with a cutting torch and be precise enough as to not damage the threads on the pipe. So with a steel lock you end up using much less heat and going much faster since you can cut such a narrow and precise kerf.

[guest5999]

makes sense. i was just curious. the body of that lock is sitting around somewhere since all i really care about is the cylinder. sloppy tolerances though :(


thanks

[ASSA]

Well, you can drill through anything, even the ceramics in the sargent & greenlef 833, given you have the right drill and enough time. If there is no need for drillprotection, a big body made from aluminium could work just fine.
It won't be top security though

I made a 3d drawing of the 833 the other day by the way, and i thought I might show it off here.
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