Materials

  • Titanium

What is titanium?

Titanium is a low-density, strong, lustrous, corrosion-resistant metal and is metallic-white in color. Its corrosion resistance is remarkable even against sea water and chlorine. It has the highest strength-to-weight ration of any metal known.

Unalloyed, it is as strong as some steels, but 45% lighter. Titanium is non-magnetic, and a poor conductor of heat and electricity. It also has high fatigue resistance and high crack resistance. Titanium is used in aircraft, armor plating, spacecraft and, because of its high corrosion resistance to sea water, is a highly-sought after material used for divers’ knives.

Grades 1 through 4 are commercially pure (unalloyed). These four are distinguished by their varying degrees of tensile strength, as a function of oxygen content, with Grade 1 being the most ductile (lowest tensile strength with an oxygen content of 0.18%), and Grade 4 the least (highest tensile strength with an oxygen content of 0.40%). The remaining grades are alloys, each designed for specific purposes, be it ductility, strength, hardness, electrical resistivity, creep resistance, resistance to corrosion from specific media, or a combination thereof.

Like aluminium and magnesium metal surfaces, titanium metal and alloy surfaces oxidize immediately when they are exposed to air. Titanium readily reacts with oxygen at 1,200 °C (2,190 °F) in air, and at 610 °C (1,130 °F) in pure oxygen, forming titanium dioxide. However, it is slow to react with water and air, because it forms a passive and protective oxide coating that protects it from further reaction. When it first forms, this protective layer is only 1–2 nm thick but continues to slowly grow; reaching a thickness of 25 nm in four years.

When exposed to nitrogen, clean titanium metal is covered with a titanium nitride layer. The thin titanium dioxide and nitride layers on titanium surfaces are very hard and inert. The most noted chemical property of titanium is its excellent resistance to corrosion; it is almost as resistant as platinum, capable of withstanding attack by dilute sulfuric acid and hydrochloric acid as well as chlorine gas, chloride solutions, and most organic acids. However, it is soluble in concentrated acids. The metal cannot be melted in open air since it burns before the melting point is reached. Melting is only possible in an inert atmosphere or in a vacuum. At 550 °C (1,022 °F), it combines with chlorine. It also reacts with the other halogens and absorbs hydrogen. Titanium is one of the few elements that burns in pure nitrogen gas, reacting at 800 °C (1,470 °F) to form titanium nitride, which causes embrittlement. Titanium powder can form an explosive suspension in air.

 

 

  • Stainless Steel

What is stainless steel?

Stainless steel is a steel alloy with a minimum of 10.5% to 11% chromium content. Stainless steel doesn’t corrode, rust or stain with water as ordinary steel does, but is not stain-proof, most notably under low oxygen, high salinity, or poor circulation environments. Stainless steel with additions of 13% chromium are high-oxidation resistant in air and water. It is also referred to as corrosion-resistant steel or CRES.

Stainless steel has a protective layer that naturally reforms when scratched, which protects the metal beneath. Stainless steel is not a good conductor of electricity, and austenitic stainless steel is non-magnetic.

Stainless steel differs from carbon steel by the amount of chromium present. Unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide, and due to the dissimilar size of the iron and iron oxide molecules (iron oxide is larger) these tend to flake and fall away.

Stainless steel is a lustrous metal alloy, and is low-maintenance, making it an ideal material for many applications, such as knives, surgical instruments, industrial equipment and it is widely used in aerospace applications.
Stainless steels contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal’s internal structure, and due to the similar size of the steel and oxide molecules they bond very strongly and remain attached to the surface

There are different types of stainless steels: when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels virtually non-magnetic and less brittle at low temperatures. For greater hardness and strength, more carbon is added. With proper heat treatment, these steels are used for such products as razor blades, cutlery, and tools.

 

 

  • G10

What is G-10?

G-10/FR-4 is a thermosetting industrial laminate consisting of a continuous filament glass cloth material with an epoxy resin binder. This product, first introduced in the 1950’s, has characteristics of high strength, excellent electrical properties and chemical resistance. These properties are maintained not only at room temperature but also under humid or moist conditions. Today what is called G-10 is actually FR-4, the flame retardant version of G-10. Both G-10 and FR-4 are rated at 285 degree F continuous operating temperature. Because they are thermosets, no melting will occur with these grades, however charring will be observed after extended periods above the temperature rating. FR-4 has a flammability rating of 94 V-0. With these outstanding characteristics, it is easy to understand why G-10/FR-4 is such a versatile material and is used in a wide variety of applications.

G-10 is a high-pressure plastic laminate glass epoxy. It has near-zero water absorption, and is not electrically conducive. Its texture makes for a great grip on knife handles. One of its desirable properties is it neither feels cold in cooler temperatures or hot in warmer temperatures. G10 is a Glass-based Epoxy Resin Laminate, which is formed by soaking layers of glass cloth in epoxy resin, and compressing them down and heating them until they set.

G10 is very similar to Micarta and Carbon Fiber Laminate, in that they are all Resin Laminates, only the base material is changed. G10 is the toughest of the Glass Fiber Resin Laminates and consequently the most commonly used. G10 is impervious to moisture, and has excellent electrical insulating properties making it useful for circuit boards and other electrical applications. It is also easy to grind and comes in many colors making it an excellent choice for knife handles and parts.

It is often used for tactical knife handles. While production knives using G10 tend to be textured, creating a grippy surface for extra purchase, custom makers tend to either bead blast G10, sand it or polish it.

 

 

  • Carbon Fiber

What is carbon fiber?

Carbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 µm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment gives the fiber high strength-to-volume ratio (makes it strong for its size). Several thousand carbon fibers are bundled together to form a tow, which may be used by itself or woven into a fabric. Carbon fiber is a composite that has a very high strength-to-weight ratio.

It is also known for its low weight, high chemical resistance, high temperature tolerance, and low thermal expansion.

When combined with a plastic resin and wound or molded it forms carbon fiber reinforced plastic (often referred to as carbon fiber) which has a very high strength-to-weight ratio, and is extremely rigid although somewhat brittle. However, carbon fibers are also composed with other materials, such as with graphite to form carbon-carbon composites, which have a very high heat tolerance.
Carbon fiber is the common name used to refer to plastic reinforced by a graphite textile.

Carbon fiber is very expensive, but has a fantastic weight-to-strength ratio. Depending on the orientation of the fiber, the carbon fiber composite can be stronger in a certain direction or equally strong in all directions. The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion, make them very popular, however, they are relatively expensive when compared to similar fibers, such as glass fibers or plastic fibers.
Carbon fibers are usually combined with other materials to form a composite.

 

 

  • Exotic

Mackrill Custom Knives is able to use some exotic materials on the handles of their custom liner lock folders and on their fixed blades. We can use handle materials such as:

– Hippo tooth ivory
– Mammoth tooth
– Mammoth tusk
– Natural African woods
– Giraffe bone
– Certain antelope horns

 

 

  • Bohler

N690 or N690Co as it is sometimes called, is a Cobalt-enriched stainless steel from Austrian steel company Bohler. N690 shares some similarities with it’s other Cobalt-steel bretheren such as ATS-55 and VG-10. N690 is similar to a sophisticated 440C with better edge-holding and stain resistance. The steel is extremely fine grained. When it comes to edge-holding, it is agreed that the finer the steel grain, the better.

Chemical composition (nominal) %:
C 1.07, Co 1.5, Cr 17, Mn 0.4, Mo 1.1, Ni -, P -, Si 0.4, S -, W -, V 0.1

Various alloying elements (chromium, vanadium, phosphorous, manganese, molybdenum, nitrogen, etc.) used in blade steel, particularly in the family of corrosion-resistant “stainless,” produce certain desirable properties (edge retention, hardness, corrosion resistance, impact strength, etc.).

One of the most exotic alloying elements is cobalt, which is known to increase hardness and strength, as well as intensifying the effects of other elements in a particular steel formulation. Typically, N690 is hardened to a factor of Rockwell 58-60. Obviously, the key here is the addition of cobalt in the steel matrix. The cobalt allows the creation of a very uniform structure within the steel. When used in blade steel, this provides a fine and consistent edge, enhancing edge retention and sharpening receptivity.

 

 

  • Sandvik

Sandvik 12C27 is a martensitic stainless chromium steel with an optimized analysis for high quality professional knife applications. After heat treatment, the composition of carbon and chromium gives a unique combination of properties including:
Very high hardness
Good corrosion resistance
Very high wear resistance

Typical applications for Sandvik 12C27 are hunting and fishing knives, pocket knives, skate blades and ice drills.

Standards
ASTM (420)/(440A)
W.Nr. (1.4034)/(1.4037)

Chemical composition (nominal) %:
C 0.6, Si 0.4, Mn 0.4, P 0.025 (max), S 0.10 (max), Cr 13.5, Mo –

Sandvik 12C27 is Sandvik’s most well-rounded knife steel with excellent edge performance allowing razor sharpness, high hardness, exceptional toughness and good corrosion resistance. Sandvik 12C27 is their main knife steel for hand-held knives, high-end ice skate blades and ice drills. Continuous improvement over a period of 45 years has evolved Sandvik 12C27 into the high performing steel grade it is today.

The composition is tighter, the purity level is much higher and the fine carbide microstructure of today is far from how Sandvik 12C27 knife steel of the sixties looked. With a hardness range of 54-61 HRC, high toughness, scary sharpness and good corrosion resistance, Sandvik 12C27 is the recommended grade for hunting knives, pocket knives, camping knives, high-end chef’s knives and tactical knives.

 

 

  • Damascus

Damascus steel was a type of steel used in Middle Eastern swordmaking. Damascus steel was created from wootz steel, a steel developed in India around 300 BC, which was further refined by Middle Eastern swordsmiths. These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water. Such blades were reputed to be not only tough and resistant to shattering, but capable of being honed to a sharp and resilient edge. The original method of producing Damascus steel is not known. Because of differences in raw materials and manufacturing techniques, modern attempts to duplicate the metal have not been entirely successful. Despite this, several individuals in modern times have claimed that they have rediscovered the methods in which the original Damascus steel was produced. The reputation and history of Damascus steel has given rise to many legends, such as the ability to cut through a rifle barrel or to cut a hair falling across the blade, but no evidence exists to support such claims.

We, at Mackrill Custom Knives, also use Damascus steel, which is made for us by top forgers and metalsmiths. There are many different techniques that bladesmiths and metalsmiths use to make Damascus knife blades. The following gives a basic idea on the process; Start with five pieces of steel, two high carbon pieces of steel and three medium carbon pieces of steel. Clean the impurities from the pieces of steel, then sandwich the two high carbon pieces between the medium carbon pieces. Arc weld them together at the end. The weld material must be removed after the first forge weld.

The billets are placed in a forge and brought to a cherry red color. They are then removed and covered with borax. The pieces are then hammered together with a hammer on an anvil. The billet is heated several times during this process.The billet is cut in the middle, leaving a little material to keep it together until it is welded again. The billet is then turned on its side and hammered enough to swell the center of the billet. The billet is then cleaned and reheated; it is then folded back on itself.

Repeat the process 5, 6, or 7 times in order to obtain 150, 300 or 600 layers respectively. The more layers there are, the more skill required for making an exotic piece of steel.

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