Angle grinder-proof bike locks - are they coming?

Angle grinders are the go-to tool for brazen bike thieves. This breed of thief carries little concern about being caught in the act.

Every week there seems to be a new video appearing online of thieves happily cutting bike locks in busy London locations using angle grinders.

Angle grinders are age restricted to 18 years old, apart from that anyone can buy one new from as little as £25, which sadly makes them a very accessible tool for thieves.

Whilst you can make it a lot harder for a thief to safely use an angle grinder, when considering your choice of bike lock (using two) and locking technique, any lock on the market can be cut (given enough time).

But could the tide turn if bike lock manufacturers are able to use a new material called ‘Proteus’?


The creators confidently report that Proteus “is non-cuttable by an angle grinder and a power drill, and it has only 15% steel density.”

This strong, but light material is named after the “capable of assuming many forms” Greek sea-god, Proteus, due to its transformable makeup.

It’s created through the following process, which includes the placement of ceramic spheres within an aluminium structure:

Manufacturing steps for Proteus

The structure is specially designed so it turns a cutting tool’s energy back onto itself. Whilst the front layer of the material is passable by the grinder, when it hits the ceramic spheres the material will vibrate. The research lead, Dr Stefan Szyniszewski, explains:

“Essentially cutting our material is like cutting through a jelly filled with nuggets. If you get through the jelly you hit the nuggets and the material will vibrate in such a way that it destroys the cutting disc or drill bit.

“The ceramics embedded in this flexible material are also made of very fine particles which stiffen and resist the angle grinder or drill when you’re cutting at speed in the same way that a sandbag would resist and stop a bullet at high speed.”

During tests, an angle grinder “achieved only a partial incision and subsequently experienced high wear.” The image below shows the wear over time on the angle grinder discs, when trying to cut through Proteus:

Angle grinder on Proteus

Final thoughts

As it’s only at the proof of concept stage, at present, there are no bike locks using this material. From this stage to actually having a material, or a product, that can be manufactured at scale is a very long journey, but how fantastic would it be to have a bike lock that could not be cut by an angle grinder?

The creators have a patent pending and have big plans for the material, not just for security but also for use in the safety industry. It’s definitely worth keeping an eye out for the developments.

The research team behind Proteus are connected to Durham University in the UK and Fraunhofer Institute for Machine Tools and Forming Technology IWU in Germany.

You can read the full 24 page research report here.

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