Are metal knives recyclable?

How to discard knives

I, being the geek that I am, decided to make one with materials that I had lying around (lie, I bought the file for less than 2 euros in a second hand market ;), but the intention is what counts).

As soon as I had in mind the general idea of what I wanted to do, I started looking for the raw material. It didn’t take me long to find in a thrift store a drawer full of rusty tools. I decided on a rather large file (in fact, too large, but I didn’t know that until well into the project) that cost me 1,75 €. I didn’t know it at the time, but it was a Nicholson brand file which, it seems, are made of very good steel.

Once we are happy with the result we must re-harden the steel so that it has tool quality and stays sharp. I won’t go into detail on the process as there are many very technical articles available on the internet; basically you have to heat the steel until it is no longer magnetic and cool it in oil, this can be repeated several times. The steel becomes very hard again (a file should slide across the surface and barely leave a mark). In this state it is also brittle and can break if struck. It needs to be tempered again to make it somewhat more flexible. This can be done in a conventional oven.

What to do with old knives

In addition to nickel and chromium, some of the most important alloying elements used in combination with steel are molybdenum, titanium, tungsten and vanadium. These metals are scarce and only available in some parts of the world, which makes their extraction very costly and difficult. It is therefore essential to recycle them to avoid depleting the planet’s natural resources.

Most of these special alloys have a very similar appearance. To separate and prepare each of these types, very sophisticated identification technology, such as X-ray spectrometry, is used. Recycling stainless steel is a similar process to that used for other ferrous metals.


Recycled metal represents a significant saving of resources. The industry’s impact on the environment is significantly reduced: pollution and mining waste is reduced by 70%, recycled aluminum pollutes 95% less than virgin aluminum, and a recycled soda can saves the equivalent of 3 hours with the television on.

Many metallic materials also have a great advantage: they can be recycled many times over. The less positive aspect is that it cannot be done at home, as the treatment processes are complicated and must be carried out in specialized plants.

Most metals can be melted down to create new metals. Aluminum, lead, iron, steel, copper, silver and gold are easily recycled when they are not mixed with other elements. They melt and change shape or adapt the same shape as before, greatly reducing production costs and environmental impact.

But what happens to metals after they are thrown away? The recycling process begins when the user separates his or her waste. The different metals are then collected and sorted, to be processed separately.

Steel 4063

By recycling iron and steel, new iron does not have to be mined, resulting in savings in mining and processing costs, including the energy required to do so. Recycling steel is as simple as sorting and then melting it together with the molten iron. At about 1,700 degrees C, the mixture becomes liquid metal that is poured into molds to be made into various products, including recycled knives.

Another technique used by blacksmiths is to apply heat to the piece of metal from which the knife is to be made (for example, a file) with red-hot charcoal and shape it with strategic mandarin blows. The steel has to be red hot because it is more difficult to shape it when it is cold. Nor can it be left too long in the forge because it can burn. It has to be made with a pure hammer blow.

Nestled in the Sierra de La Giganta, in the northwestern state of Baja California Sur, Mexico, the community of Las Animas is home to blacksmiths who transform old car parts and any metal into elaborate machetes, knives, daggers and knives. The so-called desert knives, made from recycled metals, have become an emblem of the Mexican peninsula both for their beauty and because they provide an economic livelihood for families in this arid, agriculturally hostile region.