A Is for Anvil

Metalworking Glossary for the Letter A

See the index to the Glossaries here:


  • A-axis. The A-axis is the fourth axis of a mill that is equipped with an optional rotary table, after the X, Y, and Z axes. Also called a rotary axis.
  • Abrasive Blasting. A type of deburring that employs small particles of hard abrasive grit that are projected by air or other means to debur, clean, or finish a workpiece.
  • Abrasive Wheel. A wheel designed for grinding that is made from hard abrasive materials.
  • Acme Thread. A type of screw thread with a 29° included angle. The thread height is exactly half of the length of the pitch.
  • Acute Angle. An angle that is less than 90°.
  • Adapter. A device used to allow a different size or shape of tool to fit a machine.
  • Age Hardening. Also known as just “aging,” age hardening is a process that changes the properties of a metal by subjecting a forging to a relatively low heat for a specific period following a final heat treatment or cold working operation. Aging helps stabilize a piece of metal following structural changes induced by any prior operations.
  • Air Bending. One of the most common processes used to bend metal on a press brake, air bending takes its name because of the open gap between the bottom of the material and the bottom of the die. Unlike processes like bottom bending and coining where the metal is pushed to the bottom of the die, air bending allows the operator to make a wide variety of angles in the metal based on how far the punch descends into the die. Since air bending puts less strain on the metal, springback is greater than with other bending methods. Because of this, operators will overbend to a slightly tighter angle to allow the metal to relax back to the intended radius.
  • Air Gauge. An air gauge shoots pressurized air at an object and has sensors that detect the rate at which it returns to give a measurement of the dimensions of the object.
  • Aircraft Roll. Aircraft rolls are specialized sheet metal rolls designed to form the metal outer layer of the leading edge of aircraft wings. Since wings change in shape and taper from one point to another to be aerodynamic, aircraft rolls feature forming rolls that can change in position relative to one another during the rolling process to accomplish this. They are also referred to as contour rolls or leading-edge rolls and can produce cones and other types of tapered parts.
  • AISI. Abbreviation for American Iron and Steel Institute.
  • Alloy. A hybrid material—such as alloy steel—that is composed of a metal and at least one other chemical element, usually created to increase a property of the metal such as strength, ductility, or hardenability.
  • Alloy Steel. Unlike regular carbon steel, which is an alloy of iron and carbon, alloy steel also contains additional elements added to improve the metal’s mechanical properties. Manganese is the most common alloying element and is added to improve the strength and workability of the steel. Adding vanadium will increase the steel’s strength while retaining its ductility. Elements like nickel and copper increase corrosion resistance, as does chromium, which is a major component of stainless steel. Adding lead or bismuth improves machinability, while molybdenum increases toughness, making it an ideal alloy from which to produce cutting tooling. Other alloying elements include silicon, boron, titanium, tungsten, and aluminum.
  • Angle Grinder. A handheld power tool that usually makes use of an abrasive disc or thin cut-off disc to remove excess material from a workpiece either by grinding or abrasive cutting. They are often used for finishing work.
  • Angle Iron. A piece of metal with a cross section at a right angle, shaped like the letter L.
  • Angle Plate. An angle plate is used for clamping a workpiece in a vertical position for layout, tooling, and machining, as well as being a vertical reference for inspection.
  • Angle Roll. Another name for a profile roll, an angle roll is a machine designed to curve pieces of long metal with different profiles, such as tubes, square solids, or I-beams. The popular term angle roll comes because of the machine’s common use in ornamental work to bend angle iron.
  • Annealing. A heat-treating process that increases the ductility of metal by raising it to a temperature above its critical range, holding it there long enough to permit full recrystallization, then allowing it to cool slowly.
  • Anodizing. The creation of a thin protective oxide layer on a metal subjected to an electrolytic process.
  • Anvil. Essentially the blacksmith’s workbench, an anvil is a carefully shaped tool that allows several different hand forging operations to take place, such as using the protruding horn for bending steel.
  • Apron. On a lathe, the apron is a part of the lathe carriage and is clamped to the saddle. It holds the components that propel the cross slide, such as gears and levers.
  • Arbor. In milling, an arbor is a horizontal shaft or spindle that holds the cutting tool on an arbor mill.
  • Arbor Milling. A type of milling operation that uses a milling cutter mounted on a horizontal bar called an arbor.
  • Arbor Milling Machine. Another name for a horizontal mill.
  • As Forged. A designation that refers to the condition of a completed forging without any subsequent operations.
  • Assembly. A finished machine or product after all the parts and subassemblies have been fitted together.
  • ASME. Abbreviation for American Society of Mechanical Engineers. ASME develops and publishes technical standards for a wide range of materials, products, systems, and services drawn from a voluntary consensus.
  • ASTM. Abbreviation for American Society for Testing Materials.
  • Asymmetrical 3-Roll Machine. A sheet metal roll that has two rolls, one above the other, on the side where material is fed, with an adjustable position side roll behind them. It is also known as an initial pinch roll because the two rolls on the feeding side “pinch” or clamp the material as it comes into the machine. The asymmetrical name comes because the arrangement differs from the symmetrical pyramid rolls which have a top roll centered over two bottom rolls.
  • Austenite. A solid solution of carbon or other solution components in iron.
  • Austenitic Steels. Steels containing between 16-26% chromium and up to 35% nickel, giving them high corrosion resistance, but also rendering them nonmagnetic. They cannot be hardened through heat treatment.
  • Auxiliary Operations. Additional steps applied to shape or condition the surface of a workpiece when the forging operation has been completed.
  • Axial Cutting Force. In milling, it is a cutting force that is applied in the direction of the axis of the rotating cutting tool.
  • Axial Rake Angle. One plane of measurement of rake angle (the other being radial rake angle). Axial rake is the angle of incline between the face of a cutting face and a line parallel to its axis of rotation. It determines the direction of chip disposal.
  • Axis. A straight line passing through the center of an object around which the object would rotate. Also, a reference direction in a coordinate system, such as an X-axis or Z-axis on a metalworking machine.