L Is for Lathe

Metalworking Glossary for the Letter L

See the index to the Glossaries here:


  • Lap. In forging, a lap is a type of a surface defect that appears like a seam or fissure caused by folding over an extrusion like a fin and forging it into the surface of the workpiece.
  • Lapping Plate. A lapping plate is used for accurate hand lapping (rubbing two surfaces together with an abrasive between them) to achieve a perfectly smooth, flat exterior on a workpiece.
  • Laser. The term laser—originally created as an acronym for Light Amplification by the Stimulated Emission of Radiation—refers to a machine that can focus light into a narrow, straight beam without the light spreading out. This artificially produced light beam can generate heat at the point of impact, making it an effective cutting tool in metalworking. Types of lasers used in metal fabrication include CO2 lasers and fiber lasers.
  • Laser Scanning Arm. A portable type of coordinate measuring machine.
  • Lathe. Common in woodworking, a lathe in metalworking is a machine that rotates a piece of metal at high speeds so that a tool applied to the surface of the spinning workpiece can cut or perform some other action to the metal as it makes contact. When a machinist needs to create a cylindrical part that is symmetrical, such as a screw or a gun barrel, he uses a lathe to produce it.
  • Layout. To mark or scribe the shape of a part on blank stock so that it can be machined or formed to the correct dimensions in a manually controlled operation.
  • Lead Angle. The degree of inclination of a cutting tool’s edge as it engages with a workpiece. The lead angle controls the balance between the axial and radial feed forces of the tool.
  • Leadscrew. The leadscrew runs parallel to the feed rod down the length of a lathe and transmits power from the headstock to the carriage for accurate thread cutting operations.
  • Length. A specification term regarding a metalworking machine that usually describes the overall working length of the machine, used in determining maximum workpiece capacity, rather than the full physical length of the equipment itself.
  • Level. Also called a “spirit level” because of the mineral spirit solution inside its bubble gauges, a level is used to check the levelness of any surface in relationship to the horizontal plane of the earth’s surface. A simple device, it indicates a level surface when the air bubble is exactly centered inside the clear vial of liquid that serves as its gauge. Levels are also known as “engineer’s spirit levels” and “machinist’s levels.”
  • Lever Dial Gauge. Often called a “test indicator,” it is a type of dial gauge that measures the amount its lever or probe moves in a swinging arc.
  • Live Center. In lathe work, it is a center that revolves with the work. It is usually the headstock center.
  • Low-density Cutter. A cutter containing very few inserts per inch of diameter. Also known as a coarse-pitch cutter.
  • Lower Beam. The lower section of a press brake which holds the die rail in position. They are usually stationary, made to provide resistance as a moving top beam pushes the punch into the die, but some brakes feature an up-acting lower beam that moves the die up into a punch mounted on a stationary upper beam.
  • Lubricant Residue. The carbonized residue of lubricant burned onto the surface of a part during forging. The condition of such a forging is called “baked on.”
  • Lubricity. A cutting fluid characteristic that expresses the amount friction is reduced between the cutting tooth or tool and the workpiece.