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Extrema Ratio knife was created in Prato (Italy) in 1997.

The company is active in the development, prototyping and production of civil and military knives.
Its production is based on specifications as well as on the development of new knives and pocket knives according to customers requirements.
The company peculiarity consists of having extended the high quality standards requested by the civil market to the military production.
This high quality level is obtained through the designs functionality ,the choice of the best materials and the most modern manufacturing process.


Extrema Ratio began creating knives of sport use, but today it is dedicated to the elaboration of military knives

The first military customers were special units of the Italian Army which gave a strong technical and professional impulse to the development of all the subsequent production.

Thanks to the development of specific instruments the company itself can carry out efficiency and resistance tests.

The co-operation with the Faculty of Motorial Sciences of the University of Perugia concerning thethe ergonomic aspect of the products grants the effective capability of adapting them to the user.
It also co-operates with the Faculty of Engineering of the University of Florence which carries out products tests as well as structural, material and coating analyses.
The company is certified ISO 9001 and is part of the Armed Forces suppliers’ list, NATO Code (N/CAGE): AD856.

The company of knife and penknives is coming through a considerable development on the Italian and international market.
The Extrema Ratio knife, which is technical and essential, satisfies the professional consumer which pays much attention to the innovations, but is concentrated on the functionality.

Born with the aim of producing sporting knives for civil use, of high industrial niche, it specializes soon in the production of tactical knives of the same qualitative niche.
The product is born to satisfy the demands of a civil market that is extremely specialized and hard to please as regards refinement of materials, modernity of finishing and efficacy of design, accuracy of workmanship and completeness of accessory.

In thisphase Extrema Ratio acquires that conception of quality which is typical of the civil market (where each piece is inspected by the purchaser) and extends it unchanged to the military market.
New product’s types have been added to the original one of the sporting knife; this development and gradual increase corresponds with the strategy of Extrema Ratio for the next years.

The aim consists in designing a line of pocket knives and knife in which the experience and the demands of the civil market join with the experience and the demands of the military market in order to create a new product’s concept: the standard Extrema Ratio.


The Extrema Ratio company elaborates knives of military use, police use, and services of emergencies



All processes are demanded to numerical control machinery, but every single knife receives a peculiar handcrafted care in the finishing process, mechanical adjustments and, most of all, regarding the sharping which is thoroughly performed by hand.
The choice in materials is the best among what the market offers, which contributes in giving high performance to our products.
Our knives and penknife are not art pieces, they’re simple and efficient professional technical instruments.


Our production:

Extrema Ratio produces tactical knives, that is fixed blade or openable knives for severe use.
The use of special steels, of polymers like KRATON and of processes like vacuum hardening, make our knives the best cutting instruments.
Care in details, like stainless steels screws, detachable handles, technical scabbards equipped with belts and extensions make these instruments the top. This quality results in the adoption of these instruments by important operative army units.


In the elaboration of its knives, Extrema Ratio uses special steels


As said, Extrema Ratio is a mechanical workshop, therefore we can virtually face the production of mechanical and plastic instruments.

We have chosen to take in charge the production of tactic knives but the white weapons license of production and the techical qualification for the production of common and war weapons held by the two partners open unlimited horizons in the blade production field. We can thus produce double edged blades, bayonets, automatic knives and pocket knives.

The present working area enables us to face production orders both of bulk quantities and of small amounts (50-100 pieces), upon request from military units.



Which Steel:

High quality in steel is the basis for the maximum performance and endurance of a blade produced for cutting objects (knives, scissors, precision or medical bistouris etc.). Steel must be hard in order to keep a sharp cutting edge for long, being at the same flexible enough to bend without breaking. Moreover it must be stainless and performing a high resistance to corrosion. You obtain such qualities only by using rough materials of top quality and power.

The alloy "steel":

The materials normally used by the best blades manufacturers are high carbon content "AISI (Arerican Iron and Steel Institute) 440 e AISI 420", chrome hardenable steels . In other words they are stainless martensitic steels that contain at least 12 % chrome, which potential can be developed through an appropriate building and thermic treatment cycle. Martensitic steels are made of iron, carbon and chrome alloys, sometimes enriched with vanadium, molybden, nickel and tungsten in order to increase inoxidability, hardness and toughness. The best mix, distribution and fusion of this elements allows the production of top quality steel for this knives.


The steel is an essential material for the manufacture knives


The thermic tratment also called hardening is used to exploit martensitic stainless steel qualities at their best.

When steel is mixed to other elements, it develops peculiar qualities; depending from the characteristics that need to be intensificated, use wise. A thermic treatment is what usually transforms an alloy steel into an optimum kniving steel. Any alloy steel has its own critical temperature, reaching which the steel crystal structure changes, causing the carbon solubility in the ferritic matrix to increase. Such temperature must be always kept constant in order to obtain steel austenitize, but not for too long because an increase in granulation dimension (which especially for knives blades should be kept preferrably low) must be avoided.

The next step cools down the temperature (tempering) thanks to different means (water, oil, salt emulsions, ice, air etc.) in order to achieve the hardness level you want



After tempering, steel is hard and brittle at the same time. To achieve a suitable compromise between hardness (longer life of edges) and brittleness decrease (higher resistance in crash) a second thermic treatment is carried out. Scope of this treatment is to stretch the material subject to the internal cohesion state caused by tempering and to remove any left tension.


In case of breakage of the knife it´s possible to replace a single part, instead of all the knife



You should always keep in mind that increasing the hardening point implies an increase also in permanent strain point (when material deformation changes from elastic to plastic and the tension breaking point increases) but diminishes ductility and resistance to crashes.

On the contrary, an increase in toughness and elasticity brings a higher capacity in crash absorbing, higher ductility and ease of workability, but also a decrease in deformation point.

From this examples it’s clear that if the to be treated steel is aimed at the production of knives and pocket knife, the latter treatment will be preferred, seeing less strict tempering and stronger drawing so that breaks due to crashes can be avoided. On the other hand, by using steel for blades and knives blades production, you will use a strict tempering and a soft drawing, meant to stretch the material by keeping hardness at the maximun compatible level. A very satisfying way to check these aspects is the Rockwell test, which measures hardness.



All metals, excluding precious ones like gold and platinum, tend to alter when coming in contact with atmosphere, water and with chemical industrial knives. Resistance to corrosion of stainless steels is due to the formation of a passive superficial layer, called “passive film”.

In order to let this fine layer form, the chrome percentage in steel must be over 12%. This element generates an oxide upon the metal surface able to stop corrosion. Please keep always in consideration though that all steels (even stainless ones), having a strong ferrous matrix, are subject to oxidation and only a good maintenance preserves their integrity.


Extrema Ratio uses different types from elements so that the knives do not oxodize


Alloy components:

  • Carbon: increases duration of edge and elasticity point; increases hardness and fatigue to abrasion resistance.

  • Chrome: increases hardness, elasticity and tenacity; helps in fatigue resistance and corrosion.

  • Cobalt: increases resistance and hardness and allows high temperature endurance; multiplies the effects of other elements of the alloy.

  • Copper: increases resistance to corrosion and fatigue resistance.

  • Manganese: improves capacity to hardness increase; deoxidates and degasses metals during bulk thermic treatments, increases hardness and dicreases brittleness.

  • Molybdenum: increases tenacity, capacity of hardening and fatigue resistance; increases workability and resistance to corrosion.

  • Nickel: increases resistance, hardness and resistance to corrosion.

  • Phosphorus: dicreases brittleness when in high concentrations; increases resistance, workability and hardness.

  • Sylicium: increases workability, elasticity, deoxidates and degasses many metals.

  • Sulphur: increases workability when used in small amounts.

  • Tungsten: increases resistance, hardness and tenacity.

  • Vanadium: increases resistance, hardness and crash resistance; inhibits granulation.


Belts are produced in polymers with high mechanical and chemical resistance


N 690 Steel:

QuThis kind of steel, selected for its exceptional features and used to produce all blades of knives, comes from Austria and is manufactured by a small steel plant; highly specialized in high quality special steels.

N 690 is a martensistic special steel with 17% chrome and it differentiates from AISI 440C steel thanks to a higher level of molybden (double). Not only molybden is a strong generator of carbides (improving cutting features) but increases resistance to corrosion in those steels highly connected to chrome. Moreover vanadium and cobalt alloys add ons increase the performances of this steel (vanadium is a also carbides generator with resulting increase in resistance to wear and therefore capacity of keeping edge sharpness for longer; cobalt prevents granulosity at high temperatures and improves drawing capacity and high temperatures resistance) .

This steel features high resistance to corrosion and wear, keeps a sharpened edge for longer, can be easily polished and features also high levels in hardness, over 60 HRC (more than traditional steel AISI 440 C) that can be reached through the thermic treatment of tempering.

These are the reasons why its employ is oriented towards blades and professional knives production. Thanks to the peculiar edge keeping quality and to oxidation resistance this steel is used in industrial kniving (food and fishing industries) and for butchering jobs. In the medical area, it’s mainly used for surgical instruments production.



Warranty notice:

Being EXTREMA RATIO positive about the high quality of its knives and pocket knives, guarantees a quick replacement of products (upon stock availability) in case of:

  • production fault preventing item from functionality

  • break caused by production fault or inner fault in materials used

This warranty covers our knives for unlimited time. Scabbards have a 6 years warranty, from purchase by first customer. This warranty does not cover damages due to wearing and oxidation, which can be avoided thanks to careful lubrication and polishing, even on the best stainless steels. In order to profit from this warranty, please send faulty items back along with original copy of the purchase receipt. Should EXTREMA RATIO certify the fault, the faulty parts will be replaced for free, including expenses due for shipping items back.


The knives Extrema Ratio knife have good warranties because are products of great quality



Should a repair be necessary, EXTREMA RATIO offers a customer service repairing and replacing damaged parts assistance. The costs for repairs will be communicated upon receiving of the knife and pocket knife. For our customers sharping service is free. Customers will have to pay only for shipping fees.


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