Locks and chains resistant to grinders

[billdeserthills]

Update on this, as some of my previous comments were not entirely true (though I though so at the time ):
The limitations to Oxy-Fuel Cutting are as follows:
-the melting point of the metal you are cutting must be higher than the kindling point
-the oxide that is created when the metal is exposed to oxygen in the air must melt at a lower temperature than the metal itself (ex: aluminum melts at 1250F, while Aluminum oxide melts at 3760F; Ferrous Steel melts at 2500F and Iron Oxide melts at 2500F)
-Thermal conductivity of the metal must be low enough so that the kindling temperature can be reached and maintained (ex: copper)
-Oxides formed must be fluid when molten
Examples of metals that could be cut are ferrous steel, titanium, magnesium.
Examples of metals that could not be cut are copper, aluminum, and brass.

From what I have learned there is a way to force a severance on a material like aluminum, by sandwiching it between two layers of ferrous steel, but it is unreliable. (I saw a video of it , but can't find it anymore. Let me know if you do.) Also, I can't find my source on copper being used to bind up drill bits, though I remember it was on TV or a movie. Either way, I have debunked this somewhat, in that the copper layer would need to be thick enough to bind the flutes on the drill and prevent chip from being cleared. There may be some merit to a layer of copper used to cause a drill bit to break against the next layer of steel due to the sudden release in needed pressure. In other words, you are using a rig to apply a large amount of force to drill through hardened steel, then you hit a soft layer of copper or aluminum and it punches through immediately and hits another wall of hardened steel and breaks the drill bit. Though it was not on a safe, I have experienced this first hand.

Please let me know if you have any questions, guys. I learn as you do.

So when was the last time You tried to burn through a piece of magnesium?
Did You hafta change your underwear afterwards?

[YouLuckyFox]

I am so surprised no one else has asked about that!

Here's the excerpt from my Welding textbook (see bottom right):
https://books.google.com/books?id=pUcKA ... um&f=false

[hag3l3]

From the archives of personal experience.....
many, many years ago, I was the proud owner of a brand new jvx5000 canon dale bike. Powder blue on black pin stripe custom paint. I purchased the absolute best chain and lock available on the market at that time.
Filled out the guaranteed warranty papers from the lock manufacturer.
Went to the local grocery store in Socal district, came back out, bike gone, lock cut in half through the chain, turned in warranty and lock parts to company.
learned 2 things right then and there....
1, a warranty is not covered under a known high crime area; and 2..learned this from fellow bike enthusiasts, and shop owners: a co2 converted air die grinder will slice through anything out there; it does not matter the material when the willingness is there.
I find my peace in no longer buyin what I am not prepared to lose.
hope this helps.

[Squelchtone]

careful folks.. this thread is derailing into Advanced level topics of melting metal in safe walls, the OPs question was about bike and shed locks and grinders.

Please keep it on point,
Squelchtone

[mysidia]

I guess this is really just basic elementary school chemistry; any metal can be melted by applying sufficient heat, even metal in your chains and padlocks. Doesn't seem very advanced, just brute force. An opportunistic thief using a torch against your locked chain/shed just isn't a realistic concern anyways, a grinder is more likely but still very rare, and at the same time, expecting to make a professional thief fail to force open your locked chain within 5 minutes, likely just isn't a very realistic hope in the first place,

Seeing as the professional bad guys know too many weaknesses or tricks, they will be likely to have one we can't know or anticipate.
I expect running around with an expensive oxy torch stealing bikes will be noticed very quickly by the police.

Since there's no real way to make a hardened substance significantly more resistant to cutting than thick hardened steel, without weakening it to easier attacks, making it really expensive, and making it take up larger amounts of space. For some reason, I think your best bet at resisting grinders is to just have siper thick heavy-duty chains, and to have multiple chains, where one of the chains may be "hidden" or harder to reach somehow, or add lengths of "dummy chain" in a way where it is not really obvious which chain to start cutting on, but not so much chain that the chain itself becomes a valuable target.

You might also have the length of your chains shielded or concealed by a wooden cover or something like a steel plate mounted over the area on your fence or structure where the chain is wrapped, to help impair tool access.

Or wooden material that is cheap but not very hard or strong, so it is more about making free clear wide open direct access to wide cross-sections of the chain to get a tool in there and start cutting on the metal time consuming or inconvenient.

Best if there is narrow clearance and difficult to get tension on the chain, so a cutting disk contacting the chain mostly causes the chain to just move out of the way.

Secure or lock the chain at multiple places, and loop it multiple times, so cutting the chain in one place just once doesn't free up what is being secured.

In an ideal world; I am thinking a sheath around the entire length of chain filled with some type of springy gel-like substance under pressure.. that would be formulated to cling to the cutting surface and harden, it would be nice if it could cause the grinder's zip disk blade to seize up, perhaps set off a loud alarm and hit the thief with a spray as they retract their tool and contain a purple die to mark the thief.

Probably the usage of an additional alarm on the door or tracking device on the bike is the most feasible as an added layer of protection.

[NKT]

If someone invents a material harder and tougher than steel to resist angle grinders and disc cutters? Well, they already have. Better steels, for one thing. There are very wear resistant steels that are used for locks now that are really hard to cut through, as they contain loads of carbide in the microstructure, without getting brittle.

Going further, there are various ultra-hard coatings available, and, indeed, tungsten carbide inserts are in some high end locks, but you have to recall that the 3mm rod of caride is trying to stop a 115mm diameter disc. A full size disc has a 36cm circumference. Every 3 rotations is approximately 1m of disc edge. A typical upper limit is an edge speed of 80 metres PER SECOND. So that's a lot of cutting action - even if it was ten times harder than the disc, the bolt would wear rapidly. A 10mm bolt would be hit by 800x more disc edge than it's max diameter, in the first second!

The idea of mixing hard and soft materials is a good one, but it doesn't help generally. The hard bits clear the soft bits that were clogging the disc - just like when you dress a grinding wheel on a bit of steel after some muppet has used aluminium on it. You'd have to go for a soft ali coating.

Jumping back into even deeper thread necromancy, no, you can't flame cut copper or aluminium. The copper takes the heat away too fast if it's a thick slab, and aluminium turns into aluminium oxide, which you then can't melt with your torch, and, in fact, lumps of alox are used in two places - in safes to stop carbide drills working fast, and in cutting discs, where they are actually what is doing the cutting!

(Yes, I've not been on the site in a while. Life is busy!)