I Is for Inclusion

Metalworking Glossary for the Letter I

See the index to the Glossaries here:


  • Idler. One or more gears placed between two geared shafts to transfer the rotation from one shaft to the other without changing their speed or ratio.
  • Inch per Tooth. Abbreviated as IPT, it is the measurement of feed that one insert makes in a single revolution of the cutting tool.
  • Inclusion. Inclusions are impurities like dirt, oxides and other foreign particles that are present in the metal.
  • Independent Chuck. A chuck in which each jaw may be moved independently of the others for holding irregular parts or mounting a workpiece off-center.
  • Indicator. The word indicator refers to any instrument that is used to accurately measure a small distance and amplify the results in a way to make them easily readable to a craftsman, such as through a scale, dial, or digital display. The word is often interchangeable with “gauge” (for example, a dial indicator and a dial gauge are synonymous).
  • Induction Heating. A way of heating metals by using an alternating magnetic field.
  • Ingot. A rough metal casting used as stock for forging and other operations, such as extrusion or rolling. Ingots are designed for storage and transportation.
  • Initial Pinch 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. The name originates from the clamping (or pinching) of material by the first two rolls as it is initially fed into the machine. This type of roll is also known as an asymmetrical roll since the arrangement of the rolls isn’t symmetrical, or the same on both sides, like a traditional pyramid roll.
  • Insert Density. The number of cutting edges or inserts around the diameter of a milling tool. Also referred to cutting edge density, it is measured as number of cutters per inch of tool diameter.
  • Insert Pitch. The distance between a position on a single insert in a cutter to the identical position on the next insert.
  • Inside Micrometer. A micrometer used to measure the internal diameters of a hole.
  • Internal Diameter Grinder. A type of cylindrical grinder, also called an inside diameter or ID grinder. It was developed for grinding out holes inside of hollow cylinders, with the small grinding wheel and the larger workpiece rotating in opposite directions.
  • Involute Gear. A type of spur gear with a specific type of rounded curve to the teeth.
  • Iron. A heavy metallic element native to most igneous rocks (as well as meteorites) that is ductile, malleable, and magnetic. It is the primary component of steel.
  • ISO. Abbreviation for the International Organization for Standardization, an organization that develops and publishes technical, industrial, and commercial standards worldwide.
  • Isothermal Forging. A forging process in which a constant temperature is maintained uniformly throughout a workpiece.