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Knife making is the process of manufacturing a
knife A knife (: knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least Stone Age, 2.5 million years ago, as e ...
by any one or a combination of processes: stock removal, forging to shape, welded lamination or investment cast. Typical metals used come from the
carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...
,
tool A tool is an Physical object, object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many Tool use by animals, animals use simple tools, only human bei ...
, or
stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...
families. Primitive knives have been made from bronze, copper, brass, iron, obsidian, and flint.


Materials for blades

Different steels are suited to different applications. There is a trade off between hardness, toughness, edge retention, corrosion resistance, and achievable sharpness. Some examples of blade material and their relative trade offs: *The newest
powder metallurgy Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes are sometimes used to reduce or eliminate the need for subtractive manufacturing, subtractive processes in ma ...
steels can be made very hard, but can quickly wear out abrasives and tooling. *A blade made from low carbon or
mild steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...
would be inexpensive to produce and of poor quality. A low carbon blade would be very hard to break, but would bend easily and be too soft to hold an edge. High carbon (or high alloy, in some listings) can take a much higher hardness but must be tempered carefully after heat treatment to avoid brittleness. Unusual non-metallic materials may also be used; manufacturing techniques are quite different from metal: *The natural volcanic glass
obsidian Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...
can achieve a nearly molecular edge (high achievable sharpness) and only requires
Stone Age The Stone Age was a broad prehistory, prehistoric period during which Rock (geology), stone was widely used to make stone tools with an edge, a point, or a percussion surface. The period lasted for roughly 3.4 million years and ended b ...
technology to work, but is so brittle that it cannot maintain that sharpness for very long. Additionally, The entire blade is highly susceptible to being accidentally broken. One such use of obsidian is to make extremely sharp surgical
scalpel A scalpel or bistoury is a small and extremely sharp bladed instrument used for surgery, anatomical dissection, podiatry and various handicrafts. A lancet is a double-edged scalpel. Scalpel blades are usually made of hardened and tempered ...
s. * Ceramic knives hold their edge for a long time, but are brittle.


Blade making process


Initial forging

The initial shaping of a knife is traditionally done through
forging Forging is a manufacturing process involving the shaping of metal using localized compression (physics), compressive forces. The blows are delivered with a hammer (often a power hammer) or a die (manufacturing), die. Forging is often classif ...
though stock removal or blanking can be used. Steel can be folded either to form decorative pattern welded steel or to refine raw steel, or as the Japanese call it, tamahagane. Grain size is kept at a minimum as grain growth can happen quite easily if the blade material is overheated. In a mass production environment, or in a well equipped private shop, the blanking process is used to make "blade blanks." This can be achieved by a number of different methods, depending upon the thickness of the material and the alloy content of steel to be cut. Thinner cross section, lower alloy blanks can be stamped from sheet material. Materials that are more difficult to work with, or jobs that require higher production volume, can be accomplished with
water jet cutter A water jet cutter, also known as a water jet or waterjet, is an industrial tool capable of cutting a wide variety of materials using an extremely high-pressure jet of water, or a mixture of water and an abrasive substance. The term abrasive je ...
s,
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
s or electron beam cutting. These two lend themselves towards larger custom shops. Knife makers will sometimes contract out to a shop with the above capabilities to do blanking. For lower production makers, or lower budgets, other methods must suffice. Knife makers may use many different methods to profile a blank. These can include
hacksaw A hacksaw is a fine-toothed saw, originally and mainly made for cutting metal. The equivalent saw for cutting wood is usually called a bow saw. Most hacksaws are hand saws with a C-shaped walking frame that holds a blade under tension. Suc ...
s, files, belt grinders, wheel grinders, oxy-acetylene torches, CNC mills, bandsaws, or any number of other methods depending on budget.


Grinding

If no power equipment is available, this can be done with files if the piece of steel has not yet been hardened. Grinding wheels, or small belt sanders are usually what a beginner uses. Well equipped makers usually use a large industrial belt grinder, or a belt grinder made specifically for knife making. The standard size for a knifemakers' belt grinder is a grinder that runs a belt size of 2" by 72". Pre-polish grinding on a heat treated blade can be done if the blade is kept cool, to preserve the temper of the steel. Overheating can be observed in the knife by watching for heat discoloration. Some knife makers will use a coolant mist on the grinder to achieve this.


Heat treatment

Methods of heat treatment: atmosphere furnace, molten salt, vacuum furnace, coal (coke) forge, oxy/acetylene torch. Quenching after heat treatment differs according to type of metal and personal preferences. Quenching can be done with oil, animal tallow, water, air, or brine. Most steels will require a specific temperature, soak time, and tempering heat for the different grades.


Blade finishes

The finish quality of the blade is determined by the Grit of the finishing grind. These can range from a low-shine 280-320 grit finish to a mirror-shine. The high polish shine can be accomplished by buffing with chrome oxide (ex. white chrome, green chrome), hand rubbing with extremely fine wet-or-dry abrasive paper, or with a Japanese water-stone, which has an approximate grit of 10,000-12,000. The knife might also have a different direction in scratch pattern, depending on the method of finishing.


Handle making process

Handle making can be done in several different ways depending on the tang of the knife. Full tang knives usually have handle scales either pinned, riveted, or screwed on to the tang itself while knives without a full tang may be inserted into a solid handle and then attached in one of the previously stated methods. Handle materials can range from natural materials including wood or elk horn to man-made materials like brass, plastic, carbon fiber, polymer or
micarta Micarta is a brand name for composite material, composites of various fibers integrated in a thermosetting plastic. Materials such as linen, canvas, paper, fiberglass, carbon fiber, or other fabrics are used to form products for electrical and ...
. A knife makers grinder may have additional attachments for making knife handles, such as small diameter contact wheels.


References

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