Design Guidelines GLOSSARY

NC--Numerically controlled.

N/C Press--Numerically controlled press. See "CNC Turret Press."

Nesting--(1) Grouping of identical or different parts in multiples within a workpiece to conserve material. (2) In packaging, stacking of parts whose shape permits one to fit inside another.

Nibble Marks--Slight irregularities at the edge of the stock surface after progressive punching ("nibbling") operations in a turret press.

Nitriding--The process of adding nitrogen to the surface of a steel, usually from dissociated ammonia as the source. Nitriding develops a very hard case after a long time at comparatively low temperature, without quenching.

Nominal--The targeted value for a dimension that defines the size of an ideal part.

Non-Ferrous Metal--Elements and their alloys without iron as a major constituent.

Non-Geometrical--Information not related to the shape of the product. (i.e. part number, notes, material lists, tolerances, etc.)

Non-uniform Coverage--Inconsistent paint thickness.

Normalizing--The process of heating steel to a temperature above its transformation range, followed by air cooling. The purpose of normalizing may be to refine grain structure prior to hardening the steel, to harden the steel slightly, or to reduce segregation.

Notching--Operation in which the punch removes material from the edge or corner of a strip or blank.

Nugget--Area melted together during resistance welding.

Obround--Contraction of the words oblong and round denoting a punched slot with semicircular ends and straight sides.

Observational Standard -- See "Color Chips."

Oil Canning--See "Bow Distortion."

Orange Peel--Surface condition characterized by an irregular waviness of a paint finish, resembling an orange skin texture.

Orbital Sanding--Non-straight-line abrasive finish with irregular circular marks.

Organic Coating--Designation of any chemical finish containing carbon.

Orthographic Drawing--A drawing showing a projection of a part which all the features are visible.

Outboard Mill--A roll forming machine with housings that support both ends of the roll tooling shafts.

Outside Radius--Formed outside radius of a bend.

Overlapping Seam--See "Enclosed Seam and Pocket."

Overspray--(1) Spray material which may be lost within the spray booth or to the atmosphere. (2) Spray material which subsequently falls on the product. (3) Areas adjacent to coating of surfaces requiring paint.

Oxidation--Chemical reaction between a material and oxygen.

Oxidation Scale--Stained, discolored and flaky surface condition.

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Pallet--Wooden platform, generally 42 in. wide, 48 in. deep, and 6 in. high designed to facilitate lift truck handling of parts or packages.

Pancake Die--Simple push-through die for blanking or piercing.

Parametrics--Defining a feature's size by establishing a geometric relationship between it and other features, instead of defining it with a dimension.

Pattern Direction--Orientation of features or surface patterns on sheets and coils.

Pem Fastener--Self-clinching inserted fastener (nut, stud, standoff, pin, blind stand off, etc.) made by Penn Engineering & Manufacturing Corp.

Pencil Hardness Test--Method to measure coating hardness based on the scratching of the film with pencil leads of known hardness. The result is reported as the hardest lead which will not scratch or cut through the film to the substrate.

Penetration--(1) Depth of a cutting operation before breakout occurs. (2) In welding, the depth of material through which fusion occurs.

Periphery--The extreme outer edge of part or drawing.

Perpendicularity--Dimensional relationship of a part or datum located at right angles (90°) to a given feature.

Phosphating--Pretreatment of steel or certain other metal surfaces by chemical solutions containing metal phosphates and phosphoric acid as the active ingredients, to form a thin, inert, adherent, corrosion-inhibiting chemical conversion coating which serves as a substrate for subsequent paint coats.

Phosphor Bronze--Copper base alloy with 3.5 - 10% of tin to which phosphorus has been added in a molten state in varying amounts of less than 1% for deoxidizing and strengthening purposes.

Pickled and Oiled--Hot rolled steel with the scale removed through immersion in acid and a follow up rinsing and oiling process for oxidation protection. Also referred to as "P&O" and "HRPO."

Piercing--Punching of openings such as holes and slots in material.

Pigment--Finely ground, natural or synthetic, inorganic or organic, insoluable particles which, when dispersed in a liquid vehicle to make paint, may provide, in addition to color, many of the essential properties of a paint--opacity, hardness, durability, and corrosion resistance.

Pinch Trim--Trimming excess material from a drawn part at the bottom of the stroke. Leaves drawn shell without an inside burr, but with an outside burr and a thinned edge.

Pitting (Inter-Crystalline Corrosion)--Gal-vanic attack under moist and acidic conditions between molecular structures of differing alloy content.

Plasma Arc Welding (PAW)--Specialized process utilizing a non-consumable electrode ionizing an inert gas and increasing temperature to melt the material being welded.

Plastic Deformation--Permanent deformation occurring in forming of metal after elastic limits have been exceeded.

Plate--Sheet steel thicker than 7 gauge 0.179 in. (4.55 mm) or sheet aluminum thicker than 3/16 in (4.76 mm).

Point--A piece of geometry at an exact location.

Polishing--Abrasive process in which the surface created takes on a bright reflective finish, scratch-free to the unaided eye.

Postcut Roll Forming--A process whereby the raw material is fed into the roll forming mill in coil form with the formed part cut to length. This is the most common roll forming material feeding process.

Powder Coating--100% solids coating applied as a dry powder and subsequently converted into a film with heat.

Power Spinning--The art of forming metal over a mold in one pass using hand or hydraulic pressure.

Precipitation Hardenable--Alloy in which a constituent precipitates from its supersaturated solution allowing the material to gain added strength.

Precision Lead Screw--See "Lead Screw."

Precut Roll Forming--A process whereby the raw material is cut to length prior to entering the roll forming mill and fed into the mill as blanks. Primarily used for low-volume applications.

Prefinished Material--Stock which has been painted or plated prior to fabrication or stamping.

Prenotch/Prepunch Press--A device used to stamp a hole or notch pattern in incoming material on a roll forming line prior to roll forming.

Press Attachment--A bed mounted device on a slide forming machine used for punching, piercing and other press operations.

Press Section--A device that is built into a slide forming machine used for punching, piercing and other press operations.

Primer--First application of a substance capable of adhering to the substrate and providing good adhesion to a subsequent coating.

Programmable Back Gauges--Stops on metalforming machines which can be adjusted during and between cycles by computer numeric control.

Progressive Tool--Die using multiple stations or operations to produce a variety of options. Can incorporate piercing, forming, extruding and drawing, and is usually applied to high quantity production runs.

Projection Weld Nuts (or Studs)--See "Weld Nuts" and "Weld Studs."

Projection Welding--Using protrusions on one of the two parts to be resistance welded, creating a positive conductance path.

Prototype--First part of a design which is made to test tolerance capability, tooling concepts and manufacturability.

Pull Down--Area of material next to the penetrating edge of a piercing punch, or die edge of the blanking station, where the material yields, i.e. flows in the direction of the applied force, creating a rounded edge. Also known as "roll-over."

Pulse Mode--Intermittant surging of laser cutting power action.

Punch Direction--The direction from which a tool or punch enters the workpiece.

Punch Press--Machine supplying compression force for reshaping materials.

Punch Side--Opposite side from burr side for pierced features; side on which the punch enters the material. The punch side is the burr side for blanked outside contours.

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Quenching--Cooling from high temperature, usually at a fast rate.

Quick Change Inserts--Tool sections or parts which may be changed without removing the entire tool from the press.

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Ram--Driven (movable) part of a metalforming machine.

Rear Cut Off--A device on a slide forming machine driven by a cam that is mounted on the rear shaft allowing the removal of a slug from the strip, thus providing the ability to produce a blank with special end shapes.

Repositioning--Operation in turret press fabrication denoting the release of the workholders, movement of the X axis to a new position on the workpiece, and the regripping of the workpiece so that a sheet larger than the X axis table travel can be fabricated, all under computer numeric control.

Reproducibility--Extent to which parts from multiple lots are identical.

Rerolling--Final cold rolling operation, usually done to achieve specific thickness control and improved finish.

Resins--Natural or synthetic basic material for coatings and plastics.

Resistance Projection Weld (RPW)--See "Projection Weld."

Resistance Spot Welding (RSW)--Melting and joining action of two adjoining metal surfaces created by the thermal reaction of thc metal to the flow of an electrical current forming a weld nugget.

Revision--A subsequent part drawing usually denoting new corrected or improved version.

Revision Description--A written notice de-scribing the nature of changes to a drawing.

Rivet Nut--Internally threaded fastener designed to be used as a rivet from one side of a workpiece or assembly and to provide threads for a screw or bolt to be used in assembly of a mating part.

Rockwell Hardness--An indentation hardness test based on the depth of penetration.

Roll Formed Shape, Hollow--A roll formed shape which is closed by mechanically fastening or welding the two strip edges together.

Roll Formed Shape, Open--A roll formed shape with a linear or curved contour in which the two ends of the shape are not brought together.

Roll Forming--A continuous bending operation in which sheet or strip metal is plastically deformed along a linear axis by being passed through a series of roller dies and progressively shaped to the desired contour.

Roll-Over--See "Pull Down."

Roll Stations--Tandem sets of rolls used in roll forming to shape the metal stock in a series of progressive stages to form the desired cross-sectional configuration.

Rotary Slide Machine--A vertical forming machine with the ability to place several forming slides radially around the center tool and produce intricately formed stampings and wire forms.

Roundness--Extent to which a feature is circular.

Run Out Flange--Feature on a formed part which is designated by the designer to absorb the tolerance accumulations created by multiple forming operations.

Run--Sag or accumulation in a paint or finish film prior to curing.

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Excerpt taken from Design Guidelines for Metal Stampings and Fabrications -- 2nd Edition copyright © 1995 Precision Metalforming Association

Purchase the new Third Edition of Design Guidelines for Metal Stampings and Fabrications copyright © 2004 Precision Metalforming Association at Marketplace today!

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