O Is for Oxidation

Metalworking Glossary for the Letter O

See the index to the Glossaries here:


  • Offset. A defect in a forging caused when the dies did not align properly.
  • Oil Country Lathe. An oil country lathe is a large, specialized lathe for machining long workpieces such as segments of drill strings that are used in oil field work. Oil country lathes have large-bore hollow spindles to allow large parts to fit easily through them.
  • Oil Hardening. A process of quenching alloy steel in oil to bring out certain qualities during a heat-treating procedure.
  • Oilstone. A molded fine-grained abrasive whetstone used with oil to sharpen the edges of cutting tools by hand.
  • Open Die Forging. A forging produced by working between simple dies where the flow of metal is largely unrestricted. Also called flat die forging, hand forging or smith forging.
  • Open Height. The distance between the bottom of the ram and the top of the bed when the ram is raised to the top of the stroke and no tooling is present. Open height is also called “daylight.”
  • Optical Comparator. A magnified silhouette of a part is projected on the screen of an optical comparator and inspected to verify if its geometry and dimensions are within specifications.
  • Outside Diameter Grinder. Also called an OD grinder, it is a type of cylindrical grinder designed for grinding the external surface of a cylindrical workpiece.
  • Outside Micrometer. A micrometer used to measure the outside diameter of a circular object.
  • Oxidation. The degradation of a material when exposed to oxygen for too long of a period. Oxygen combines with the material, changing its chemical makeup. Oxidation of a metal results in discoloration, cracking, and corrosion (such as rust).