Heavy Duty Security Chains: How to Choose the Right Grade for Your Application

Case hardening strengthens the outer surface of the steel while leaving the core softer. Through hardening treats the steel throughout the entire link, giving it a more consistent level of resistance from the surface to the centre.

For lower-risk jobs, a case-hardened chain can still offer useful protection. Once the hardened outer layer is breached, though, the softer core can become easier to cut, so it may be less suitable for high-value equipment or exposed locations.

Through-hardened chains are better suited to applications where cutting resistance is the priority, such as securing motorcycles, machinery, tools or equipment stored outdoors. Because the steel is hardened throughout the link, there isn’t a softer core beneath the surface once an attack begins.

For a heavy duty security chain guarding plant, containers or fixed machinery, the Locks Direct 16mm Security Chain is the thickest link we sell, built from case hardened Grade 8 alloy steel with added boron. That mix of thickness and hardening lets it resist sustained cutting, not just a single quick attack, which is exactly what a site left empty overnight needs.

A step below it, the Locks Direct 13mm Security Chain uses the same case hardened Grade 8 alloy in a lighter link. It's built for outdoor objects and gates, where the full 16mm is more than the job needs. Thirteen millimetres also sits close to the link size industry buying guides point to as the threshold for a chain to reach Gold-level ratings.

Want a stated outside grade rather than a house score? The Squire TC14/4 Security Chain carries a 14mm hardened steel link with Sold Secure Powered Cycle Gold. The Squire SS65CS & TC14/4 chain and padlock set pairs that chain with a CEN Grade 6 padlock, the highest attack rating a padlock of that type can carry. Both give a site manager an outside-tested figure to point to, not just our own score.

For most outdoor applications, zinc plating provides a practical layer of protection against the elements. It helps shield the steel from moisture and corrosion, making it well suited to chains used in yards, sheds, garages and other exposed locations.

Some chains use a protective sleeve instead. Squire chains, for example, cover the hardened steel with a fabric-style sleeve that helps protect the chain from the weather while also preventing it from marking painted or finished surfaces.

The best option depends on where the chain will be used. A zinc-plated finish is a strong choice for general outdoor security, while a sleeved chain can be especially useful around motorcycles, gates, painted equipment or anything else you want to protect from scratches.

The Squire G3 Security Chain is a strong option if you want a high independent security rating without stepping up to one of the heaviest chains in the range.

It uses 10mm hardened alloy links and comes in a 915mm length, with a Sold Secure Pedal Cycle Diamond rating. That makes it particularly well suited to securing valuable bikes and other applications where strong resistance is needed without the extra bulk of a 14mm or 16mm industrial chain.

Its smaller link diameter also makes it easier to handle and carry, which can matter just as much as outright thickness when the chain needs to be used regularly.

By comparison, the 8mm Squire X4 is a lighter option for lower-risk applications where portability and ease of use matter more than achieving a specific independent security rating.

Length is about reach. A chain needs enough slack to loop around what you're securing and reach a fixed anchor point. Leave a bit extra too, so it isn't pulled tight against an edge that could wear through a sleeve over time. A short chain paired with a nearby ground anchor is usually easier to manage than a long one looped loosely, because slack chain gives a thief more room to work a tool into.

Diameter is a trade-off that runs one way. A thicker chain fights back harder, and it's heavier to carry every time you use it. There's a real point past which a chain gets too heavy for daily use, most of all on a bike you lift on and off most days. That's why the 10mm and 13mm chains sit alongside the 16mm, instead of everyone reaching for the biggest link. Match diameter to how exposed the item is, and to how often you'll pick the chain up yourself.

For fixed sites where containers or machinery are left overnight, our 13mm and 16mm chains are the heavier-duty options in the range and better suited to static security.

Bike security calls for something easier to handle. A Sold Secure Gold-rated chain with a protective sleeve works well here, particularly when it’s secured to a suitable ground or wall anchor.

If you want an independently rated chain without moving into the bulkier industrial options, the Squire G3 is a strong place to start. Its 10mm links keep it manageable, while the Sold Secure Pedal Cycle Diamond rating gives you recognised independent testing.