Aluminum Extrusion Glossary

6063 Alloy – A common aluminum alloy for architectural extrusions, known for its excellent finishing characteristics (especially for anodizing), good corrosion resistance, and medium strength.
Alloy – A substance with metallic properties composed of two or more chemical elements of which at least one is a metal. Aluminum plus one or more other elements, produced to have certain specific desirable characteristics.
Aluminum Extrusion – A manufacturing process where aluminum alloy, heated to a malleable state, is forced through a shaped die, creating a continuous length of a specific cross-sectional profile.
Aluminum Profile / Extruded Profile – The resulting shape created by the extrusion process. This can be solid, hollow, or semi-hollow, forming the basis for architectural trims and other components.
Backer (back-up plate) – A tool, or reinforcing part, which presses against the outer surface of an extrusion die, supporting it against the pressure of the extruding metal. The backer has an opening larger than the die aperture, allowing the extruded product to emerge without marring its soft surface.
Bar – A solid extrusion that is long in relation to cross section, which is square or rectangular (excluding plate or flattened wire) with sharp or rounded corners or edges; or is a regular hexagon or octagon; and in which at least one perpendicular distance between parallel faces is 0.375 inch or greater. (Smaller sizes are classified as wire.)
Billet – Commonly a cylindrical form of the aluminum alloy used in the extrusion press. Formed at casting houses and shipped either in long logs or cut into specific lengths for extrusion press applications.
Circumscribing Circle Diameter (CCD) – The diameter of the smallest circle that can completely enclose the cross-section of an extruded profile. It’s a key factor in determining extrusion press size and cost.
Concentricity – Conformance to a common center.
Die Assembly – An extrusion press will use associated tooling to hold the die in place in the press itself.
Die Holder – The press components that are located between the container and press platen to retain the extrusion die and its components. It may take many different forms and added functions depending upon its design.
Die Ring – A cylindrical sleeve that holds the die and backer in axial relationship to each other.
Die Slide – The extrusion press component located between the container and press platen. It supports, aligns to the press and retains the tooling (die, backer, bolster, sub-bolster, etc.) for the specified profile, as a unit. It may be designed to facilitate butt shearing and to provide die accessibility for replacement and repairing.
Die Stop – A defect resembling a weld around the entire extruded section, caused by stopping a press during extrusion and then restarting it.
Die Tool Assembly – The various components making up the assembly within the tool carrier or Die Slide. A typical example would be (from front to rear) a die and backer enclosed in a die ring, bolster and possibly a sub-bolster or spacer.
Die Weld – A region in extruded hollow profiles created by two streams of metal within the die joining them in the weld chamber around the mandrel of a hollow type die. Die welds are generally present in all extruded hollow profiles and in most cases are not visible.
Die, Hollow – A steel extrusion tool which forms extruded closed profiles containing one or more voids such as rectangular tubing. The tool often consists of a die cap which generates the outer surface of the profile and the mandrel or core which generates the inside contour. Hollow or semi-hollow profiles are produced usually with either bridge, porthole or spider type dies. Extruded sections produced on such dies have seams or longitudinal weld lines due to the metal flow around the web supports that hold the mandrel. The latter determines the inside contour of the profile being extruded. After flowing around the supports, the metal is fused in a weld chamber before passing through the die.
Die, Semi-hollow – A circular steel extrusion tool which forms an open profile with a high tongue ratio. Generally this tongue ratio is greater than three to one. This type of die is similar to a hollow die. The tongue is protected by a web or bridge which reduces the billet pressure. When possible, for maximum support the tongue should be bolted to the web.
Die, Solid – A steel disk, with one or more orifices of similar cross-section and contour as the desired product, through which metal is forced forming open profiles such as bar, channel and angle.
Die – An extrusion tool with an opening through which heated aluminum is forced by pressure creating the shape of the opening in the die.
Dove-tail – An interlocking connection frequently used for the assembly of interconnecting extrusions.
Extrude – To force material through a die by pressure.
Extrusion Direct – Method of extruding where the die and ram are at opposite ends of the billet and the product and ram travel in the same direction.
Extrusion Indirect – Method of extruding where the die is at the ram end of the billet and the product travels through the hollow ram and in the opposite direction.
Feeder Plate – Plate employed in front of the extrusion die to alter the metal billet dimensions permitting extrusion of larger dimensioned product than normally possible or to assist in extrusion of difficult profiles.
Flow – A term used when referring to the movement of aluminum through the die during the extrusion process.
Hollow Billet – A billet prepared for extruding seamless tube or pipe. The outside diameter may be scalped and the inside diameter may be bored or cast hollow to assure sound metal.
Hollow Dies – Extrusion tools capable of forming profiles with voids where such dies are typically classified as either bridge, porthole, or spider types. Extruded sections produced on these dies have one or more seams or longitudinal weld lines, due to metal flow around the supports that hold the stub mandrel. The stub mandrel determines the inside contour of the section being extruded. After passing around the supports, the metal is fused in a weld chamber before passing through the die proper.
Hollow Profile – An extruded profile, where any part of the cross section completely encloses a void.
O.D. – The nominal overall measurement of tube or pipe outside diameter measured across its outer perimeter because of variations in actual wall thickness, it does not necessarily indicate true dimensions at all location.
Open Space Dimension – A dimension across part of an extruded cross-sectional shape that only partially encloses a space, whose length includes more than 25 percent space, versus metal.
Porthole – A die having a stationary core or mandrel that is held in place by integral core supports or webs. The porthole die is a modification of the spider die, except that the spider is replaced with a chambered disk that supports the mandrel (sometimes termed a stub mandrel); several portholes running through it annularly about the mandrel, distinguish the porthole types. The die contains a weld chamber so that when the billet is pushed the metal divides to flow around the core supports and welds together in the welding chamber before passing through the die. Porthole dies are used in producing extruded hollow profiles and tubing.
Press, Extrusion – The hydraulic machine which applies pressure to an aluminum billet inside a container, extruding it through the opening of a die.
Profile, Extruded – A profile produced by hot extruding.
Profile, Hollow – A profile, any part of whose cross section completely encloses a void.
Profile, Semi-hollow – A profile any part of whose cross section is a partially enclosed void the area of which is substantially greater than the square of the width of the gap. The ratio of the area of the void to the square of the gap is dependent on the class of semi-hollow profile, the alloy and the gap width.
Profile – A product that is long in relation to its cross-sectional dimensions, having a cross-section other than those of wire, rod, bar, and tube, produced by extrusion, rolling, drawing, or cold finishing. Formerly termed a shape.
Rib – An elongated projection on a shape, forging or casting to provide stiffening.
Runout Table – Table at the immediate exit of press leadout equipment, which helps to guide and support the extrusion.
Seam – The junction line of metal that has passed through a hollow die, separated, and rejoined at the exit point. Seams are present in all extruded hollows produced from the extrusion process and in many cases are not visible.
Seamless – A hollow product which does not contain any line junctures resulting from method of manufacture.
Semi-Hollow Profile – A profile that has a partially enclosed void in its cross-section, often appearing as a C-channel or U-channel with very narrow openings.
Solid Dies – A steel disk with one or more orifices or apertures of the same cross-sectional area and contour as the desired product, through which metal is forced. Such dies are generally employed where profiles other than hollow are required. If solid dies are used for hollow profiles then a mandrel actuated by the action of the ram must be employed. These may be fixed or floating mandrels which require hollow billets.
Solid Profile – An extruded shape where the cross-section does not contain any enclosed voids or hollow spaces.
Spider Die – An extrusion die for producing hollow shapes, whose mandrel is supported by multiple legs attached to the cap. Metal flows between the spider’s legs and reunites before emerging through the die aperture.
Stretch Straightening – The process of stretching extruded sections beyond the yield strength of the alloy to achieve longitudinal straightness.
Temper – The combination of hardness and strength imparted to a metal by mechanical or thermal treatments and characterized by certain metallurgical structures and mechanical properties determining temper designation.
Tensile Strength – In tensile testing, the ratio of maximum load to original cross-sectional area. Also called Ultimate Strength.
Tolerance – Aluminum extrusions are produced to standard dimensional tolerances, unless otherwise specified.
Transverse Weld – A condition existing within an extrusion which is created by the interface of two separate billets. In practice the interface is extruded at different rates through the die and is formed into a conical or pointed configuration within a portion of the extrusion.
T-Slot Extrusion – A type of aluminum extrusion profile designed with T-shaped slots along its length, allowing for easy assembly and reconfiguration of structures, often used in modular framing.
Tube – A tube that does not contain any line junctures metallurgical welds resulting from the method of manufacture. This product may be produced by die-and-mandrel or by hot-piercer processes. Tube produced by porthole-die extrusion, bridge-die extrusion, or welding processes is generally not considered seamless. Seamless tube is typically used for fluid-carrying applications under pressure.

Anodic Coating – The protective and decorative oxide layer formed on the surface of aluminum during the anodizing process.
Anodizing – An electrochemical process that converts the surface of aluminum into a durable, corrosion-resistant, porous oxide layer. This process is commonly used for protective and decorative finishes.
Architectural Color Palette – Refers to a specific range of colors and finishes (often muted, earthy, or metallic tones) preferred by architects and designers for building exteriors and interiors, which require high durability and fade resistance.
Bright Dip – Chemical polishing of aluminum, often by treatment with a mixture of nitric acid and phosphoric acid, yielding a mirror like highly reflective surface. It is almost always followed by anodizing to protect the surface and provide some choice of colors.
Brushed Finish – A mechanical finish created by abrading the aluminum surface with abrasive belts or pads, creating a directional, satin texture.
Buffing – Mechanical finishing in which fine abrasives are applied to a metal surface by rotating fabric wheels for the purpose of applying a lustrous finish.
Chemical Polishing – Improving the surface luster of the aluminum surface by chemical treatment.
Clear Anodize / Satin Anodize – A common anodized finish that enhances aluminum’s natural metallic appearance while providing protection, often resulting in a satin or matte look.
Color Anodize – An anodized finish where organic dyes or electrolytic coloring methods are used to impregnate the porous anodic coating with various colors before sealing.
Conversion Coating – Chemical layer formed on the metal in the pre-treatment process which aids in paint adhesion and corrosion resistance.
Curing (Powder Coating) – The process in powder coating where the applied powder is heated to a specific temperature, causing it to melt, flow out, and chemically cross-link to form a hard, durable film.
Electrostatic Application – The method used in powder coating where powder particles are given an electrical charge to ensure they adhere evenly to the grounded aluminum part before curing.
Electrostatic Spraying – Application of a coating by applying a static electricity charge to the droplets of a spray and an opposite charge to the part being sprayed, which then attracts the droplets directly to its surface.
Etching – Shaping or texturing a metal surface by controlled corrosive action.
Film Thickness – The depth of applied coating, expressed in mils, 1/1000 inch.
Gloss – The degree to which a surface reflects light, generally, the smoother the surface, the higher the gloss.
Hard Coat Anodizing – A combined electrical and chemical finishing process for aluminum that produces a hard, colored, protective film on the surface.
Lapping – A method of finishing metal to produce a very smooth, highly accurate surface.
Mill Finish – Mill finish is the finish obtained by standard extrusion practices and produced without the aid of any subsequent operations. This finish generally varies from a structural finish with surface imperfections to an architectural finish with uniformly good appearance.
Polished Finish – A mechanical finish that creates a smooth, reflective, mirror-like surface on the aluminum.
Polishing – Smoothing a metal surface, usually by rubbing with fine abrasives. A mechanical finishing operation for the purpose of producing a gloss or luster on the surface of a product.
Powder Coating – Application of a coating in the form of a finely ground powder of coloring agents, resins, and additives; heating of the part, either before or after powder deposition, fuses the powder into a continuous coating.
Pre-treatment – The chemical alteration of a surface to make it suitable for application of paint or powder. The process usually includes cleaning and applying a conversion coating.
Sealing (Anodizing) – A post-anodizing process that closes the pores in the anodic coating, enhancing its corrosion resistance and dye retention.
VOC (Volatile Organic Compounds) Free – A benefit of powder coating, as it typically contains no VOCs, making it a more environmentally friendly finishing option compared to many liquid paints.
Wet Paint / Liquid Coating – A traditional finishing method involving the application of liquid paint, typically containing solvents, which then dries or cures. Often contrasted with powder coating.

Architect – A professional who designs and plans buildings and other structures, often specifying precise details like architectural aluminum trims.
Architectural Finish – An architectural finish is a standard finish characterized by a uniform appearance. This finish is most often specified for exposed surfaces.
Architectural Trims – A broad category of extruded aluminum profiles used to provide clean, finished edges, transitions, and aesthetic details in interior and exterior architectural applications.
Base Trim – Aluminum profiles used at the bottom of walls, providing a durable and aesthetic transition between the wall and the floor.
Chamfer – An angled or beveled edge applied to an aluminum profile for aesthetic purposes or to reduce sharp corners.
Commercial Millwork – Custom-fabricated wood, metal, or other materials used for interior finishes in commercial buildings, such as cabinetry, wall panels, and reception desks.
Corner Bead – A general term for a trim used to protect and finish external (outside) corners of drywall, often available in different materials and profiles.
Cove Trim – A concave, rounded trim profile often used at the intersection of a wall and ceiling or two perpendicular surfaces to create a smooth transition.
Drywall Bead – A metal trim accessory used to protect free edges of drywall ranging in thickness from 1/2″ to 5/8″.
Drywall Trim – Specific aluminum profiles designed to be integrated with drywall surfaces, creating clean, precise edges, reveals, or shadow lines without the bulk of traditional trim.
Drywall – Drywall is a building material, also known as wallboard, gypsum board, or plasterboard, used for interior walls and ceilings.
Flange – A projecting flat rim or edge on an extrusion, often used for attachment, reinforcement, or to create a specific overlap.
Inside Corner – A trim profile designed to create a clean, finished appearance for internal (inside) corners where two walls meet.
Interior Designer – A professional focused on planning and designing interior spaces to be functional, safe, and aesthetically pleasing, frequently incorporating modern trim solutions.
J-Bead / J-Channel – A common drywall trim profile shaped like a “J” or “U,” used to provide a clean, finished edge where drywall terminates against another surface or material.
L-Bead / L-Channel – An aluminum trim with an “L” shaped cross-section, used to create a crisp, protective corner or edge where two surfaces meet at a right angle.
Manufacturer – A business that makes goods on a large scale using machinery. Many manufacturers utilize aluminum extrusions for components in various industries.
Millwork Trim – Aluminum profiles designed to complement or integrate with wood, laminate, or other paneling in commercial casework, cabinetry, doors, and other custom interior features.
Millwork – Refers to custom-fabricated woodwork designed and made for a specific building or interior space. Examples of millwork include crown molding, wall paneling, custom cabinetry, trim, and stair banisters.
OEM (Original Equipment Manufacturer) – A company that manufactures parts or components that are then sold to another company for use in their final product. OEMs often use custom aluminum extrusions in their product designs.
Panel Hanger / Z-Clip – An interlocking aluminum extrusion system used to securely hang wall panels, signs, or artwork, providing a hidden fastening solution.
Reveal – An intentional, recessed linear gap created between two surfaces or materials using a specialized aluminum extrusion, providing a clean line and architectural interest.
Shadow Line – Similar to a reveal, a shadow line trim creates a recessed detail that casts a subtle shadow, enhancing depth and definition in a wall or ceiling system.
Wall covering – A material such as wallpaper, vinyl, laminate, wood veneer paneling, or textured fabric used as a decorative covering for interior walls.

Age Softening – A sudden decrease of strength and hardness that takes place at room temperature in certain strain hardened alloys containing magnesium.
Aging – Precipitation from solid solution resulting in a change in properties of an alloy, usually occurring slowly at room temperature (natural aging) and more rapidly at elevated temperatures (artificial aging)
Alumina – Aluminum oxide produced from bauxite by a complicated chemical process. It is a white powdery material that looks like granulated sugar. Alumina is an intermediate step in the production of aluminum from bauxite.
Aluminum Oxide – A chemical compound of aluminum with oxygen, which forms immediately on an unprotected aluminum surface exposed to air. Aluminum Oxide does not flake off, but forms a protective layer that blocks further oxidation and so protects the integrity of the metal. It is transparent and does not alter the appearance of the aluminum surface.
Aluminum – A silver-white soft metal, noted for its lightness, high reflectivity, high thermal conductivity, nontoxicity, and corrosion resistance. It is the most abundant metallic element, comprising about 1/12th of the earth’s crust. It is never found in nature as an elemental metal, but only in combination with oxygen and other elements. In ordinary commercial and industrial use, the word aluminum is often understood to mean aluminum alloy, rather than the pure metal.
Artificial Aging – An aging process that results in increased strength and hardness using a heating oven.
Bauxite – One of the ores from which alumina is extracted and from which aluminum is eventually smelted. Bauxite usually contains at least 45 percent aluminum oxide, and the best grades have a low silica content. About 4 pounds of bauxite is required to produce 1 pound of aluminum.
CAD – Computer Assisted Design. The use of computer programs to generate, analyze and modify designs. Extrusion dies and their supporting tools, for example, may be designed with the aid of computers.
Caustic – The active ingredient in an alkaline bath, generally with a pH higher than 10, which removes aluminum from used extrusion dies by etching. The primary ingredient, caustic Soda, dissolves the aluminum alloy by chemical reactions with no effect on the steel die.
Conductivity – The ability of a substance to transmit heat, light or electricity. Aluminum has a high electrical and thermal conductivity, making it useful in a wide range of electrical and heat-exchanging applications.
Deburring – Removing burrs, sharp edges, or fins from metal parts by filing, grinding, or tumbling in a media that removes the burrs from the aluminum.
Ductility – The property that permits permanent deformation before fracture by stress in the tension.
Electrical Conductivity – The capacity of a material to conduct electric current. For aluminum, this capacity is expressed as a percentage of the International Annealed Copper Standard (IACS), which has a resistivity of 1/58 ohm-mm2/meter at 68ºF and an arbitrarily designated conductivity of unity.
Fabricated Aluminum Parts -Extrusions that are cut, drilled, or machined to meet specific application needs.
Forming – Changing the shape of metal except by shearing or blanking without intentionally altering its thickness.
Grain Size – A measure of crystal size, usually reported in terms of average diameter in millimeters, grains per square millimeter, or grains per cubic millimeter.
Hardness – Resistance to plastic deformation, usually by indentation. The term may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting.
Heat Treating – Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties. Commonly used as a shop term to denote a thermal treatment to increase strength. Heating for the sole purpose of hot working is excluded from the meaning of this definition.
Heat-Treatable Alloy – An aluminum alloy that can be hardened to produce desired properties by a controlled cycle of heating and cooling.
Kerf – The notch or slit made by a saw or torch when cutting.
Lap Joint – A joint formed with one member overlapping the other.
Nitriding – The introduction of nitrogen into the surface of tool steel by holding at a suitable temperature in contact with a nitrogenous material, usually ammonia, to produce a hard wear resistant case.
Non-Heat Treatable Alloys – Aluminum alloys that are strengthened by cold working and not by heat treatment.
Oxide – A chemical compound of oxygen with another element. Hydrated (water-including) iron oxide is called rust; it does not cling tightly to the underlying metal, so the oxidation process is progressive and iron easily rusts away. Aluminum oxide is a hard, transparent compound which clings tightly to the underlying metal and protects it against further oxidation.
Pipe – Pipe that does not contain any line junctures (metallurgical welds) resulting from the method of manufacture. This product may be produced by extruding or by drawing, using either die-and-mandrel or hot-piercer processes. (Typically used for fluid-carrying applications under pressure.)
Prototype Extrusions -Initial samples created to test and refine custom aluminum designs before full production.
Quenching – Controlled rapid cooling of a metal from an elevated temperature by contact with a liquid, gas, or solid.
Reflectivity – Ability of a surface to reflect light and other electromagnetic radiation. Aluminum has high reflectivity
Slip-fit – A joint assembled by sliding two mating parts together in the direction of their length.
Snap-fit –  A self-locking joint whose mating parts exert a cam action, flexing until one part slips past a raised lip on the other part, preventing their separation.
Soft Alloy – A general term loosely describing most alloys of the 1xxx, 3xxx, or 6xxx series.
Strength/Weight Ratio – The relationship between the structural strength of a material and its weight. The strength-to-weight ratio of structural aluminum alloys is about twice that of mild steel.
Thermal Break -A barrier in aluminum frames that reduces heat transfer, commonly used in energy-efficient windows and doors.
Thermal Conductivity – The ability of a material to transmit heat through its bulk and, by direct contact, to other substances. Aluminum is a good heat conductor and is widely used in cookware and in radiators and other heat exchangers.
Tongue and Groove Joint – A joint in which one part has a groove which receives a projection (tongue) on the other part, shaped to fit snugly.
Viscosity – That property of a liquid which enables it to resist flow. High viscosity means a fluid resists flowing; low viscosity means it flows readily.
Yield Strength – The stress at which a material exhibits a specified permanent set. The offset used for aluminum and its alloys is 0.2 percent of gauge length. For aluminum alloys, the yield strengths in tension and compression are approximately equal.

Abrasions – Light marks or scuffs on the metal surface generally caused by handling or packing materials.
Blister – A raised area on the surface of an extruded product due to subsurface gas expansion during extrusion or thermal treatment.
Bow – Longitudinal curvature of rod, bar, shapes, and tube. Bow is measured after allowing the weight of the extrusion to minimize the deviation. Bow can be caused by a non-uniform extrusion rate across the cross section resulting in one portion of the extrusion being longer than the other or non-uniform contraction during quenching.
Burrs – A thin ridge of roughness left by a cutting operation such as trimming, shearing, sawing, and machining.
Chatter – A surface defect consisting of alternating ridges and valleys at right angles to the direction of extrusion.
Corrosion – The deterioration of metal by chemical or electrochemical reactions with substances in the environment.
Die Line – A longitudinal depression or protrusion formed on the surface of drawn or extruded material. Die lines are present to some degree in all extrusions and are caused by a roughening of the die bearing.
Elongation – The percentage increase in distance between two gauge marks that results from stressing the specimen in tension to fracture. The original gauge length is usually 2 inches for flat specimens and round specimens whose diameter is 0.5 inch, or four times the diameter for specimens where that dimension is under 0.5 inch. Elongation values depend to some extent upon size and form of the test specimen. For example, the values obtained from sheet specimens will be lower for thin sheet than for thicker sheet.
Flow Line – Lines on the surface of painted sheet, brought about by incomplete leveling of the paint. The line pattern revealed by etching, which shows the direction of plastic flow on the surface or within a wrought structure.
Inclusion – Foreign material in the metal or impressed into the surface.
Line Flow – The line pattern which shows the direction of flow on the surface.
Orange Peel – Surface roughening on formed products which occurs when large grains in the metal are present. An irregularity in the surface of a paint film resulting from the inability of the wet film to level out, or become smooth after being applied, thus resembling the surface of an orange. This finish may be considered desirable or a defect depending on the end use.
Salt Spray – Corrosion test using salt, sprayed as a mist in a heated humidity chamber to simulate seashore conditions, or to accelerate corrosion at a controlled rate.
Speed Tear – A series of surface cracks perpendicular to the extruding direction. Speed tearing normally occurs in corner radii or extremities of a section and is caused by localized high temperature.
Straightness – The absence of divergence from a right (straight) line in the direction of measurement.
Stress Cracking – cracking resulting from selective directional attack caused by the simultaneous interaction of sustained tensile stress at an exposed surface with the chemical or electro-chemical effects of the surface environment.
Twist – A departure from straightness.