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Bar stock, also (colloquially) known as blank, slug or billet, is a common form of raw purified
metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...
, used by industry to
manufacture Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary sector of the economy. The term may refer to a r ...
metal parts and products. Bar stock is available in a variety of
extrusion Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...
shapes and lengths. The most common shapes are round (circular cross-section), rectangular, square and
hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is d ...
. A bar is characterised by an "enclosed invariant convex cross-section", meaning that
pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circular ...
s, angle stock and objects with varying diameter are not considered bar stock. Bar stock is commonly processed by a sequence of
saw A saw is a tool consisting of a tough blade, Wire saw, wire, or Chainsaw, chain with a hard toothed edge used to cut through material. Various terms are used to describe toothed and abrasive saws. Saws began as serrated materials, and when man ...
ing,
turning Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates. Usually the term "turning" is reserved for the generation of ...
,
milling Milling may refer to: * Milling (minting), forming narrow ridges around the edge of a coin * Milling (grinding), breaking solid materials into smaller pieces by grinding, crushing, or cutting in a mill * Milling (machining), a process of using ro ...
,
drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross section (geometry), cross-section in solid materials. The drill bit is usually a rotary Cutting tool (machining), cutting tool, often multi-point. The bit i ...
and grinding to produce a final product, often vastly different from the original stock. In some cases, the process is partially automated by specialized equipment which feeds the stock into the appropriate processing machine.


Process and types

Most metal produced by a
steel mill A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-fini ...
or aluminium plant is formed (via
rolling Rolling is a Motion (physics)#Types of motion, type of motion that combines rotation (commonly, of an Axial symmetry, axially symmetric object) and Translation (geometry), translation of that object with respect to a surface (either one or the ot ...
or
extrusion Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...
) into long continuous strips of various size and shape. These strips are cut at regular intervals and allowed to cool, each segment becoming a piece of bar stock. A good analogy is
pasta Pasta (, ; ) is a type of food typically made from an Leavening agent, unleavened dough of wheat flour mixed with water or Eggs as food, eggs, and formed into sheets or other shapes, then cooked by boiling or baking. Pasta was originally on ...
-making, in which lumps of dough are extruded into various
cross-sectional In statistics and econometrics, cross-sectional data is a type of data collected by observing many subjects (such as individuals, firms, countries, or regions) at a single point or period of time. Analysis of cross-sectional data usually consists ...
shapes; cut into lengths; and then dried in that form. The cross-sectional shapes of pasta vary from simple bar or tube shapes (such as
linguine Linguine (, ; English: ; sometimes anglicized as linguini) is a type of Italian pasta similar to fettuccine and trenette, but elliptical in section rather than flat. It is about in width, which is wider than spaghetti, but not as wide as fettu ...
or
penne Penne () are an extruded type of pasta in the shape of tubular pieces with ends cut at an angle. They are usually made from wheat flour. Etymology ''Penne'' is the plural form of the Italian ''penna'' (meaning "feather", but "pen" as well), de ...
) to more elaborate extrusions (such as
rotelle ''Rotelle'' is a type of pasta resembling wheels with spokes. They are similar to '' fiori''. The name derives from the Italian word for a small wheel. In Italy they are also called ''ruote'', and in the US they are often called "wagon wheel ...
, fiori, or rotini). The same is true of metal bar stock. The most common shapes are round bar (also called rod), rectangular bar (including square bar, the special case of equal sides), and hexagonal bar (usually called hex bar for short).
Tube Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/electronica producers Arndt Rör ...
and
pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circular ...
are similar, but have hollow centers and are traditionally not called "bar" in industrial usage. (However, a product called hollow bar, essentially tube but with custom-orderable OD and ID and thus custom wall thickness, is marketed for lathe bar work which can benefit from obviation of drilling and rough boring.) Also similar in concept, but not called "bar", are the common structural shapes such as angle stock and channel stock. These are commonly available in steel and aluminum; the names "angle iron" and "channel iron" are still commonly used (informally) even though their literal namesake,
wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...
, has been replaced by steel and aluminum for most uses. In a
machine shop A machine shop or engineering workshop is a room, building, or company where machining, a form of subtractive manufacturing, is done. In a machine shop, machinists use machine tools and cutting tool (machining), cutting tools to make parts, usua ...
, bar stock and plate are often called ''billet'', although in a
rolling mill In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simi ...
, that word refers to a piece of metal that has not yet been rolled into bar. A machine shop typically has a storage area containing a large variety of bar stock. To create a metal component, a bar of sufficient volume is selected from storage and brought to the machining area. This piece may then be sawed, milled,
drilled Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at rat ...
, turned, or
ground Ground may refer to: Geology * Land, the solid terrestrial surface of the Earth * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical circ ...
to remove material and create the final shape. In turning, for large-diameter work (typically more than , although there is no universal threshold), a piece of the bar is cut off using a horizontal bandsaw to create a ''blank'' for each part. The blanks are then fed into a chucking lathe (chucker) which chucks each one in turn. For smaller-diameter work, the entire length of bar stock is more often fed through the spindle of the lathe. The entire bar rotates with the spindle during the part-machining cycle. When the cycle ends and one part is done, the chuck opens, the bar is pulled or pushed forward ("fed") by any of various automatic means, the chuck closes, and the next cycle begins. The last step of the cycle is to cut off the machined part from the bar, which is called "parting it off" and is achieved with a "cutoff" or "part-off" tool, a
tool bit In machining, a tool bit is a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool, as distinguished from other cutting tools such as a s ...
that grooves the bar all the way down to the centreline, causing the part to fall off. Then the cycle repeats. The not-yet-cut bar protruding from the back of the spindle, rotating quickly, can present a safety hazard if it is sticking out too far and unconstrained from bending. Thus sometimes long bars must be sawn into shorter bars before being fed as "bar work" (which is the term for such work). CNC lathes and screw machines have accessories called " bar feeders", which hold, guide, and feed the bar as commanded by the CNC control. More advanced machines may have a " bar loader" which holds multiple bars and feeds them one at a time into the bar feeder. Bar loaders are like magazines for part blanks (or pallets for milling work) in that they allow lights-out machining. The bar loader is filled with bars (or the magazine or pallet with part blanks) during working hours, and then it runs during the night unattended. Given that there is no human around to detect if something went wrong and the machine should stop, there are various kinds of sensors that are used to detect this, such as load meters, infrared beams, and, in recent years,
webcam A webcam is a video camera which is designed to record or stream to a computer or computer network. They are primarily used in Videotelephony, video telephony, live streaming and social media, and Closed-circuit television, security. Webcams can b ...
s, which are placed inside the machine tool's enclosure and allow remote viewing of the cutting action.


Uses of bar stock

Bar stock is widely used in many industries and can be seen in many different industrial processes. These processes include
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 ...
,
extrusion Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...
,
machining Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...
, and many more. In forging, billets are heated to high temperatures before a press pushes the
workpiece A workpiece is a piece, often made of a single material, that is being processed into another desired shape (such as building blocks). The workpiece is usually a piece of relatively rigid material such as wood, metal, plastic, or stone. After a ...
into the shape on the die. These presses operate at very high forces to make the desired changes to the product. Extrusion uses rollers that push the heated bar stock through a set of dies which will determine the shape of the workpiece. Machining is a subtractive process that utilizes bar stock and various cutters and tools to make intricate details that are not possible through other processes.


Standard sizes throughout a supply chain

To
stock Stocks (also capital stock, or sometimes interchangeably, shares) consist of all the Share (finance), shares by which ownership of a corporation or company is divided. A single share of the stock means fractional ownership of the corporatio ...
every possible size of bar stock (every possible fraction of a millimeter or inch in diameter or thickness) is impossible. Thus, bar stock is stocked by metals supply houses in various standard sizes, arrayed in discrete steps. For example, round bar with diameters of even millimeters (or in the US, on the eighths of an inch) can usually be ordered from standing
stock Stocks (also capital stock, or sometimes interchangeably, shares) consist of all the Share (finance), shares by which ownership of a corporation or company is divided. A single share of the stock means fractional ownership of the corporatio ...
. Bar diameters of nonstandard sizes can also be obtained, but only as a separate mill run from the
rolling mill In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simi ...
. Thus they are much more expensive than the standard sizes, can take much longer delivery time, and are not desirable as inventory for the supply house or the machine shop (because the chance of selling or using any particular custom size is slim). Sometimes it is necessary that the bar not be very much larger than the intended part, because the
metallurgical Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the ...
properties of some metal
alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...
s in some finishing processes may vary by how far inside the bar the metal lies. Thus an
engineering drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number of ...
will specify a certain size (or a maximum size) that the bar may start out as. These specs face the aforementioned limitation of stocking sizes versus custom mill runs; standard sizes are used wherever possible to avoid wasted expense and needless delays.


Drill rod

A drill rod is
tool steel Tool steel is any of various carbon steels and alloy steels that are particularly well-suited to be made into tools and tooling, including cutting tools, dies, hand tools, knives, and others. Their suitability comes from their distinctive ...
round stock
ground Ground may refer to: Geology * Land, the solid terrestrial surface of the Earth * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical circ ...
to a tight tolerance diameter; it is usually ± . In the UK the name "
silver steel Silver is a chemical element; it has symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. Silver is found in ...
" is often
synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...
ous and sometimes hyponymous. Its origin was in reference to the shiny ground appearance (not to any
silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
alloying content). Drill rod diameters range from ; in the United States diameters smaller than th of an inch () are made in letter drill sizes and number drill sizes, in addition to fractional sizes. Lengths are usually . It is commonly used to make
drill bit A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In orde ...
s, taps,
reamer A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precisio ...
s, punches,
dowel pin The dowel is a cylindrical shape made of wood, plastic, or metal. In its original manufactured form, a dowel is long and called a ''dowel rod'', which are often cut into shorter ''dowel pins''. Dowels are commonly used as structural reinforceme ...
s, and
shaft Shaft may refer to: Rotating machine elements * Shaft (mechanical engineering), a rotating machine element used to transmit power * Line shaft, a power transmission system * Drive shaft, a shaft for transferring torque * Axle, a shaft around whi ...
s. Note that the numbered sizes are different from the drill numbered sizes starting at 52. These sizes are: Drill blanks have an undersize tolerance of +0/−, while reamer blanks have an oversize tolerance of −0/+0. Some mills also sell square stock that is held to the same tolerances under the name "drill rod". Commonly available material grades in the U.S. are A2, D2, M2, M42, O1, S7, W1, and
high speed steel High-speed steel (HSS or HS) is a subset of tool steels, commonly used as cutting tool material. Compared to high-carbon steel tools, high-speed steels can withstand higher temperatures without losing their temper (hardness), allowing use of f ...
(including M2/M7).


Ground flat stock

''Ground flat stock'' is annealed steel that has been
ground Ground may refer to: Geology * Land, the solid terrestrial surface of the Earth * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical circ ...
to close tolerances (compare to
drill rod Bar stock, also (colloquially) known as blank, slug or billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products. Bar stock is available in a variety of extrusion shapes and lengths. The most common ...
). There are four types of materials available: O-1 tool steel, A-2 tool steel, A-6 tool steel, and
1018 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 ...
(low-carbon or low-carb steel). Lengths are either long, various widths up to are available, and thicknesses range from . Some geometrical sizes are known as '.


See also

*
Dowel The dowel is a cylindrical shape made of wood, plastic, or metal. In its original manufactured form, a dowel is long and called a ''dowel rod'', which are often cut into shorter ''dowel pins''. Dowels are commonly used as structural reinforceme ...


References

{{Reflist Metalworking terminology Steels