McGuire Glossary of Fastener Terminology

L - 75 terms

LIME COATED WIRE - This is a dipped coating not normally suitable for extruding without applying a lubricant by wire drawing. Lime is the lubricant carrier but can be used in some applications (nuts) where extrusion is not required.

LACQUERING, CLEAR - Used for decorative finishes. Color matched for color and lustre.

LADLE ANALYSIS - The results of the chemical analysis of a test sample taken during the pouring of a melt. Also called Heat Analysis

LAG SCREW SHIELD ANCHOR - This anchor comes in two lengths (short & long) and are made up of two parts that are preassembled. The interior part of the anchor is threaded to accept lag screw threads. The outer part is ribbed from the bottom of the anchor to three-quarters up the length of the anchor bolt. Lag screw shields are made from a Zamak material that is rust resistant.

LANCING - A piercing or slitting operation in which the workpiece is sheared and bent to create a pocket-shaped opening in the metal sheet. Lancing modifies the geometry of the workpiece without removing any material.

LAND - (1) The short straight section of a forward extrusion die that forms the extruded diameter. (2) The short straight section of a backward extrusion punch that forms the extruded hole diameter. (3) The short straight section of a piercing punch that forms the pierced hole diameter.

LAP - (1) A fold of material on the outside surface of a part that has been closed without fusion. (2) A process used during the tooling manufacture to polish the inside surfaces of the inserts and to refine the internal dimension of the assembled insert.

LAPS - Surface defects caused by folding over fins or sharp corners into the surface of the material.

LATHE COILING - Pulling wire around an arbor to produce springs cold working process.

LAYOUT - (1) Transferring drawing or sketch dimensions to templates or dies for use in sinking dies. (2) A detailed inspection operation in which significant dimensions of a forging are checked against blueprint specifications.

LAYOUT SAMPLE - A plaster, lead, or forged alloy sample taken from new dies to verify accuracy by layout and precise measurement.

LEAD - (1) Axial movement of a threaded part rotated one turn in its mating thread. (2) The axial distance from one point of the thread to the corresponding point on the next thread which is on the same helix as the first thread.

LEAD ANGLE - The angle between the helix of the thread at the pitch line and a plane perpendicular to the axis of the thread.

LEAD ERROR - A variation in the distance between the threads of a screw.

LEAD FREE - Solder that contains no lead (meets up and coming industry standrds).

LEAD PROOF - A reproduction in lead, or a lead alloy, of the die impression, obtained by clamping the two dies together in alignment and pouring molten metal into the finish impression.

LEAD THREAD - The thread length from where it starts to where it becomes a full-size thread. This distance on machine screws is usually one half the screw diameter.

LEAD TIME - Time required to manufacture a product from order placement until availability.

LEAD-IN CHAMFER - The tapered end of a fastener which assist the ease of insertion.

LEAD-IN CHAMFER - The tapered end of a fastener which aids insertion into the hole.

LEAD-TIN - Silver-gray dull coating. Applied in hot-dip method. Helps lubricity.

LEAN ENTERPRISE - The efficient performance of all aspects of an organization, from the beginning of the supply chain, thru the production process, including the customer base.

LEAN MANUFACTURING - The philosophy of continually reducing waste in all areas and in all forms.

LEDEBURITE - The eutectic of the iron-carbon system, the constituents being austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below the Ar1.

LEFT HAND WOUND - Also referred to as "reverse wound", design term signifying the counter-clockwise winding direction of a pitched coil.

LEFT-HANDED THREAD - A thread which, when viewed axially, winds in a counterclockwise and receding direction. All left-hand threads are designated LH.

LEG (STAPLE ANATOMY) - LEG - Spans the height of the staple

LEGACY ACCEPTANCE CRITERIA - A past version of an ICC-ES anchor qualification criteria. These are no longer current standards, but are the basis for legacy allowable load data for anchors in concrete. These standards have been replaced by modern standards such as ICC-ES AC193 and AC308

LENGTH - The length of a headed fastener is the distance from the intersection of the largest diameter of the head with the bearing surface to the extreme point, measured in a line parallel to the axis of the fastener. Exceptions: The length of a flat top countersunk head tubular rivet (with chamfered top) is measured from the intersection of the bearing surface with the shank diameter to the extreme point. The length of a headless fastener is the distance from one extreme point to the other, measured in a line parallel to the axis of the fastener.

LENGTH (NAIL ANATOMY) - Distance from the bottom of the head to the point of a nail

LENGTH OF THREAD ENGAGEMENT - The length of thread engagement of two mating threads is the distance between the extreme points of contact on the pitch cylinders or cones, measured parallel to the axis.

LENGTH OF THREAD ENGAGEMENT - On Setscrews, the length of thread engagement does not have a noticeable effect on axial and torsional holding power, provided there is sufficient engagement to prevent thread stripping during tightening. In general, the minimum recommended length of engagement is 1 to 1.5 times the major diameter of the setscrew for threading in brass, cast iron and aluminum; and 0.75 to 1 times the diameter for use in steel and other materials of comparable hardness. Be aware that the lengths of engagement specified are for full thread engaged, not overall screw length.

LENTIL HEAD SCREW - Term for oval head screws - NO longer in common use.

LEVEL LOADING - The smoothing or balancing of the work load in all steps of a process.

LEVELING - The ability of an electroplating solution to produce a surface smoother than that of the substrate.

LEVELING ACTION - The ability of a plating solution to produce a surface smoother than that of the substrate.

LEXAN(R) (PC) (PLASTICS) - Polycarbonate exhibits the highest impact strength ove a range of temperatures from -60F to 270F. It is fine for all precision parts, or where transparency is desired. Its water-clear transmittance (89%) makes it excellent for visors or guards. It shows good creep resistance and has a temperature-independent dielecric constant, as well as good insulating properies.

LIFT - The distance away from the face of the dies that the transfer fingers move on a PMP transfer.

LIFTOUT - The mechanism also known as knockout.

LIGHT TORQUE - 1/3 of initial installation value i.e. MIL spec.

LIMIT LOAD - The maximum expected applied load, including load transferred across joints as a result of thermally induced loading of the structure; it does not include preload or changes in preload occurring as a result of temperature change.

LIMITS OF PERMISSIBLE ERROR - (Of a measuring instrument), are the extreme values of an error permitted by specifications, regulations, etc. for a given measuring instrument.

LIMITS OF SIZE - The limits of size (commonly referred to as 'Limits') are the applicable maximum and minimum sizes.

LINE BALANCING - The equalization of the cycle times for units of the manufacturing process, through the proper assignment of workers and machines to ensure smooth production flow.

LINE DRIVE - The Line screw drive is a Japanese system with male, female and female tamper-resistant screw configurations. There is a wide number of designations for Line drive screws used mainly in electronics.

LINEAR SPRING - Term used to identify a straight length of flat wire having a sinusoidal waveform. Used as a compression spring.

LINK MOTION - A modified motion produced wen the slide connections are driven by a crankshaft, eccentric shaft, or eccentric gears Link motions can produce constant velocity, fate approach, or slowdown through the working part of the press stroke.

LIQUID NITROCARBURIZING - A nitrocarburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature.

LIQUID PENETRANT INSPECTION - A test method for finding cracks and discontinuities in fasteners. Parts are dipped in due and inspected under ultraviolet light. Typical on aerospace fasteners and fasteners that will see high loads.

LIVE TOOLING - Axial or radial driven tools held in the turret of a lathe and used to perform secondary operations such as drilling or tapping.

LOAD - (1) The force required to do the forming operations. It is typically measured at tits maximum point which is at the front dead center, It is expressed in either Tons, Metric Tons, or kN. (2) A term used to describe the procedure for the assembly of inserts into a case.

LOAD - Force applied to a spring that enables it to move

LOAD (SPRING TERM) - The force applied to a spring that causes a deflection.

LOAD FLANK - For threaded fasteners, the top portion of each thread which applied the preload or load pressure to the mating threads.

LOAD VECTOR ANGLE - An analysis tool used during the tooling design process to check for the proper thickness of supporting fillers and hardplates.

LOBULAR DESIGN - A design used on nut setters that has more of a rounded shape in the opening end. This design reduces stripping damage of hex head fasteners by driving the fastener on the sides instead of on the corners.

LOCK - In forging, a condition in which the flash line is not entirely in one plane. Where two or more plane changes occur, it is called compound lock. Where a lock is placed in the die to compensate for die shift caused by a steep lock, it is called a counterlock.

LOCK PINS AND COLLARS - A headed and externally grooved mechanical device designed for insertion through holes in assembled parts. A cylindrical collar is swaged into the external groove as the lock pin is hydraulically tensioned. Collar are either smooth bored or may contain a fit-tab. An optional flange provides a built-in washer

LOCK-OUT® DRIVE - LOCK-OUT® is a new innovative security screw featuring a unique patented drive that is engineered to perform in high torque applications. The distinctive oval center pin and multiple drive/key combination gives customers the option to select higher levels of security in a tamper-proof fastener. The keys are not sold commercially, only through a distributor. Manufactured by Parker Fasteners

LOCKBOLT FASTENER - A two-piece fastener comprising of a pin and collar; e.g. Avdelok(r) or Maxlok(r). Access is required to both sides of the joint and installation is achieved by swaging the collar onto the locking grooves of the pin.

LOCKED DIES - Dies with mating faces that lie in more than one plane.

LOCKING FEATURE - A device, chemical substance, or other physical characteristic added by design to one or more elements of a threaded fastening system to resist vibration-induced loosening or to provide retention against complete disengagement of the fastening elements. Preload-induced friction forces between mating joint members, mating threads, or under the head or nut elements of a fastening system inherently resist loosening; however within this NASA Technical Standard, THE TERM LOCKING FEATURE, IS USED TO REFER ONLY TO THE ADDED DESIGN ITEMS DESCRIBED ABOVE. + Prevailing Torque feature: Fastening system design that relies on friction to resist fastener rotation independent of preload (i.e. deformed thread or locking patch). + Adhesive locking feature: Fastening system design that uses chemical compounds added at the time of assembly (i.e., anaerobic adhesive, epoxies, urethanes, etc.). + Mechanical locking feature: Fastening system design employing non-friction elements usually involving a hard stop (i.e. cotter pins or safety wire).

LOCKING GROOVES - A set of grooves on the pin of a lock bolt, into which the collar is swaged.

LOCKING TORQUE - A measure of the performance of a self-locking device. i.e. resistance to rotation. Typically in is the "off" direction, not to include torque required to induce or relieve a parts axial load (pre-load). See Breakaway Torque.

LOOPS - (Also known as hooks or eyes) Formed anchoring points at the ends of extension springs that provide for attachment and force application. (the term "Hook" is generally used when it is partially open. a "Loop" is generally fully closed).

LOOPS (SPRING TERM) - Circular formed ends of extension springs that provide a means for attachment and force application.

LOT - Quantity of product of one-part number that has been processed under the same conditions from the same heat treatment lot and produced from one mill heat of material. The term Lot is also a collection of units of product submitted for inspection at one time.

LOT SAMPLING - This is a random sampling of parts from any given lot for dimensional inspection. There are certain standards which can dictate this or customer requirements can dictate.

LOT SIZE - The Lot Size is the number of units of product contained in the lot. The lot size determines sample size.

LOW CARBON STEEL - Steels containing less than 0.25% carbon; insufficient carbon content to provide a predictable, uniform response to heat treatment. Also, low tensile strength, but it is cheap and malleable.

LOWER PUNCH - The lower part of a die, which forms the bottom of the die cavity and which may or may not move in relation to the die body; usually movable in a forging die.

LOX-RECESS - The LOX-Recess screw is designed with four overlapping square recesses, with 12 contact points, and is designed to increase torque, decrease wear, and avoid cam-out.

LUBRICANT - A material applied to dies, molds, plungers, or workpieces that promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part.

LUBRICANT RESIDUE - The carbonaceous residue resulting from lubricant burned on the surface of a hot forged part.

LUGS - The anti-rotation feature applied to fasteners, also referred to as ribs.