lancing

Cutting along a line in the workpiece without producing a detached slug from the workpiece.

land

(1) Sharpening land the reduced area of a die block or punch that is reground when sharpening is needed. (2) Cutting land - see die life.

lap

See superior hone.

laser beam cutting

A cutting process that severs material with the heat obtained by directing a laser beam against a metal surface. The process can be used with or without an externally supplied shielding gas.

lead hit

(1) (Lead Shear) A method of determining the location of the cutting edge on a steel by building approximately one-fourth inch of lead on top of the cutting edge and shearing lead with mating steel. (2) A method of checking how much space is between mating form or flange steels.

leader pins

See guide pin.

level

“Measurement system analysis developed by the Shainin Consultants.  The measurement system is compared to process variation.  The goal is to have a discrimination ratio of 6 or greater for the process variation divided by the measurement system variation, where discrimination is equal to product variation divided by measurement variation.  The formulas are as follows:  The discrimination ratio =  P/ M.  M is measurement variation; P is the process variation; l is the measured length of the process variation along the axis of the best fit line.   M and P can be derived using the following formulas:  l 6 , l² =m² = 2  p² ,  p= ( l ²/2m²/2).  A short cut is to measure M and l directly from the Isoplot and use l/m8.5 (Shainin, D., Shainin, P. D., & Shainin, R. D., 1988-1993, p.37-77). “A given value or specific setting of a quantitative factor, or a specific option of a qualitative factor, that is included in the experiment.  The levels of a factor selected for study in the experiment may be fixed at certain values of interest, or they may be chosen from many possible values.” (Moen, R. D., Nolan, T. W., Provost, L. P., 1991, p.404).

leveler lines

Lines on sheet or strip running transverse to the direction of roller leveling.  These lines may be seen upon stoning or light sanding after leveling (but before drawing) and can usually be removed by moderate stretching.

leveling

The flattening of rolled sheet, strip, or plate by reducing or eliminating distortions.  See stretcher leveling and roller leveling. The process whereby a coil of steel is flattened through several sets of opposing rollers which first overbend the blank and then progressively bend to true flatness. See Figure L1 for a pictorial representation of the leveling process.

leveling blocks

Blocks used to control the shut height and levelness of a die in a spotting press.  Also called stand-off blocks.

lifter

A mechanism for raising a part in a die to a height for advancing it to another station, as in a progressive die, or for ejecting it from the die.  Also incorrectly called a kicker or ejector.

liftout

The mechanism also known as knockout.

limit switch

A type of electric switch used to control the operations of a machine automatically.

limiting dome height

The greatest depth that a material can withstand under the pure stretching of a hemispherical punch.  This is a standard measurement of stretchability. See Figure L2 for a schematic of the limiting dome height test.

limiting draw ratio (LDR)

The greatest ratio of blank diameter to punch diameter that can be successfully cup-drawn to a particular depth.  This is a standard measurement of drawability. See Figure L3a – b for a depiction of the limiting draw ratio tooling setup. See deformation limit.

line dies

A sequence of stamping dies to perform operations for completing a part.

locating pin

See pilot or gage pin.

locator

(1) See jig borer.  (2) Lower section of a die on which the part nests.  Also called an adapter, boss, die post, horn, master, master plug, and stool.

lock bead

“A ridge constructed around a die cavity to completely restrict metal flow into the die” (American Iron and Steel Institute and Committee of Sheet Steel Producers, 1984, p. 137).

lock spleen

See locking bead.

locking bead

A bead or projection designed to prevent metal flow in a forming operation.  Also called lock spleen.

low profile screw

A special socket head cap screw which has a head height approximately one-half that of a nominal socket head cap screw.

low spot

Generally, a local inboard condition on a panel which is usually in a high stress area.  Also called birdbath or shadow.

lubricant

“Any substance interposed between two surfaces in relative motion for the purpose of reducing the friction and/or wear between them” (Automotive Steel Partnership, 1991, p. 10).

Luders lines

Elongated surface markings or depressions, often visible with the unaided eye, that form along the length of a round or sheet metal tension specimen at an angle of approximately 55' to the loading axis.  Caused by localized plastic deformation, they result from discontinuous (inhomogeneous) yielding.  Also known as Luders bands, Hartmann lines, Piobert lines, or stretcher strains.