McGuire Glossary of Fastener Terminology

R - 101 terms

RACK PLATING - A frame for suspending and carrying current to articles during plating and related operations.

RADIAL LINE - A line on the surface of a nut that extends out like a circle radius for identification purposes.

RADIAL STRESS (Hoop Stress) - Forces that propagate from the fastener towards the outside diameter of the joint.

RADIAL WALL(B) - Width of a retaining ring when measured from inside to outside edge.

RADIUS RUN - OUT (RRO) - Radius Run Out offers the smooth radius in the root of the thread continues right up to the point where the thread blends in the shank of the screw. This design feature was designed for rolling high strength aerospace bolts. Flat thread rolling dies with sharp corners on the run out threads generates stress concentration areas which result in fatigue cracks in the thread rolled screw.

RAIL FEEDER - A screw feeding machine

RAISED RING ANVIL - An anvil with a protruding lip used to cold flow panel material into a self-clinching fastener from the opposite side it is installed.

RAM - The main reciprocating member of a press, guided in the press frame, to which the punch or upper die is fastened.

RAM ADJUSTMENT - The distance that a press ram position can be altered to change the shut height of the die space. The adjustment can be made by hand or by power mechanism.

RATE - Change in force per unit deflection, generally given in N/mm.

RATE (SPRING TERM) - Change in load per unit deflection, generally given in pounds per per inch (lbs/in) or Newtons per millimeter)N/mm).

RCSC - Research Council on Structural Connections

RCSC - The Research Council on Structural Connections

READINESS - Having all t=of the tooling required to form a part complete, checked, and assembled ready to put into the machine.

REAM TO FINISH - To finish a drilled or punched hole very accurately with a rotating fluted tool to the required diameter.

REAMER - Tool used for enlarging holes previously formed by drilling or boring.

RECESS - Indent or form an impression in the end of a part.

RECESS DEPTH - The distance measured parallel to the fastener axis from the intersection of the head surface with the maximum diameter of the recess to the bottom of the recess.

RECESS DIAMETER - The diameter measured in a plane perpendicular to the axis of the fastener over the intersection of the outermost extremities of the recess with the head surface.

RECESS ECCENTRICITY - The amount that a recess in a recessed head is eccentric with the shank of the fastener.

RECESS WIDTH - The distance measured in a plane perpendicular to the axis of the fastener across the intersection of the sides or wings of the recess with the head surface.

RECESSED HEAD - A head having a specialty formed indentation or recess centered on it stop surface. Two common forms of recessed heads are the 'Cross Recess' and 'Clutch Recess.'

RECEX - The Recex drive system claims it offers the combined non-slip convenience of a Robertson drive during production assembly and Phillips for after market serviceability. The Phillis Screw Company offers both Phillips and Pozidrive combo heads with Robertson.

RECTIFER - A device that converts alternating current into direct current by virtue of a characteristic permitting appreciable flow of current in only one direction.

RECUTTING - Recutting is hat happens when chips are not removed fast enough and the cutting tool hits them again. Recutting can result in a bad surface finish or excessive tool wear.

REDUCED DIAMETER BODY - A body the diameter of which may range from the minimum pitch diameter to the minimum major diameter of the thread and is common on screws having rolled heads. Sometimes, referred to as 'undersize body', which term is not recommended.

REDUCED SHANK BOLT - A bolt whose shank diameter is smaller than the nominal diameter of the bolt (normally the shank diameter of such a bolt is approximately equal to the effective diameter of the thread).

REDUCTION AREA - Usually expressed as a percentage for forward and backward extrusions. It is the percentage difference between the starting a area and the extruded area.

REDUCTION OF AREA - A measurement like elongation which is related to the tensile strength of a fastener. While elongation measures the length of a fastener stretched to its breaking point compared to its original length, reduction of area measures the diameter of a fastener just before breaking compares to its original diameter.

REFERENCE DIMENSION - A reference dimension on a fastener is a dimension without tolerance used for information purposes only. It does not govern production or inspection operations.

REFLOW OVEN - Oven that melts the solder and adheres the product to the PCB and allows for set temperatures within different zones.

REJECTION NUMBER (Re) - The rejection number is the minimum number of defects for a specific characteristic in any given sample resulting in the rejection of the lot.

RELATIVE HARDNESS - Hardness becomes a significant factor when the difference between setscrew point and shafting is less than 10 Rockwell C scale points. Lack of point penetration reduces holding power.

RELAXATION - The loosening of the connection between a bolt and a washer/nut.

RELAXATION - The loss of clamping force in a bolt that occurs typically without any nut rotation occurring. Commonly, occurs because of embedment but can also be due to gasket creep, metal creep (at elevated temperatures), differential thermal expansion and stress relaxation. The loss of force with time when deflected to a fixes position. Dependent upon, and increases with, the magnitude of stress, temperature and time.

RELIEF - The amount one plane surface of a piece is set below or above another plane, usually for clearance or for economy in machining.

RELIEF ANGLE -

RELIEF ANGLE - The transition angle between the extrusion land and the relief diameter.

RELIEF DIAMETER - A slightly larger diameter after the extrusion land in a forward extrusion insert. A slightly smaller diameter after the extrusion land on a backward extrusion punch or pin. The purpose is to minimize the friction between the formed part and the tooling

RELIEVING KICKOUT - A machine mechanism normally found on Singe Die Double Stroke Headers and Three Blow Two-Die Headers where the die kickout Pin retracts slightly between the cone and finish blow to allow for better fill on the finished part or to help get a better trim.

REMOVAL NOTICE - Also referred to as a "radius notch" or "scallop", this standard of Sprirolox Retaining Ring design feature is used to facilitate removal of the ring from tits groove by means of a screwdriver or similar type tool.

RENE 41® - Rene 41(r) is a precipitation hardening, nickel-based high temperature alloy processing high strength in the 1200/1800 degree F or (649/982 degree C) temperature range.

REPETITION RIVETING - Refers to Avdel Speed fastening system

REQUIRED STRENGTH - The factored loads and factored load combinations that must be resisted by an anchor.

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

RESIDUAL RANGE - Deflection of a spring available beyond the maximum working position up to the solid position.

RESIDUAL STRESS - Stresses mechanically induced by set removal, shot peening, cold working, forming or other means. These stresses may or may not be beneficial, depending on the application of the spring, wireform or stamping.

RESIDUAL STRESS - Stress inducted by a cold working process such as edgewinding. It may or may not be beneficial, depending upon the application.

RESIST - (1) A material applied to a part of a cathode or plating rack to render the surface non-conductive. (2) A material applied to a part of the surface of an article to prevent reaction of metal in that area during chemical or electrochemical processes.

RESOLUTION - Represents the smallest reading unit provided by an instrument.

RESOLUTION (GAGING) - The smallest increment on the full scale display of the amplifier. For example, the Edmunds air and electronic columns have a full scale with 100 graduations. Therefore, the resolution is 1/100th of the full scale value. Restriction - A device used to control air pressure or flow within an air gage amplifier. This may be done with a fixed orifice of a precise size, with adjustable needle values, or with both

RESTRIKING - Restriking is an operation that involves the sharpening of radii, form, or detail in an already formed area of the part. It can be also be defined as the finishing of forming features that could not be attained in the prior operation.

RETAINER - A part of the die block or tool holder used to keep the die or tool assembly in place.

REVERSE DRAWING - The process of redrawing sheet metal parts, resulting in the sheet metal being drawn in the opposite direction to the first draw. During reverse drawing, the intermediate part is flipped over prior to being placed on the die foe the upcoming operation.

REVERSE FORMING - A technique used when the formed part is inverted by exchanging the normal punch and die tooling as as to improve the blank control during the transfer motion or converting a rotating transfer process into a straight across transfer process.

REVERSE THREADS - The reverse threads help to pull down debris and works perfectly together with the small head size to create clean finish. The reversed threads even make it possible for the screw to be collated.

REVERSE TONNAGE - An event that occurs during flat type blanking or piercing operations when a large amount of forward tonnage is rapidly released. Reverse tonnage or snap thru results in significant damage to the stamping press.

REVERSE WOUND - (See Left Hand Wound)

RIB - A relatively flat (but generally with draft) thin portion of a forging, generally perpendicular to the forging plane.

RIBBED NECK - A style of neck consisting of longitudinal ribs around the shank adjacent to the undersize of the head.

RIBBED SHANK - A style of insert with a knurl on the shank OD. The knurls are typically aligned with the long axis of the part and begin just under the head and extend toward the thread. Knurl length is typically equal to the counterbore length.

RIBS - Small ridges of material usually formed longitudinally around the shank.

RIDGE - That portion of the thread from that contains material.

RIGGING - A system of ropes, cables, chains, slings and various equipment and/or vehicles employed to move, unload and assemble presses at their final location. Also the term used with the use of drop forged eyebolts, turnbuckles and the like

RIGHT HAND WOUND - Design term signifying the clockwise direction that a Spirolox Retaining Ring is normally wound.

RIGHT-HAND THREAD - A thread which, when viewed axially, winds in a clockwise and receding direction. All threads are right-hand threads unless otherwise designated.

RING GAUGE - An inspection tool for evaluating an externally threaded part against it allowed tolerances. See Go Gauge, NO-GO Gauge.

RING ROLLING - The process of rolling metal between rotating rolls. This increases the diameter of a metal part and reduces the ring wall section.

RING SHANK - Small directional rings on the shank to prevent the nail from working back out once driven in; commonly used for flooring, sheathing, drywall and decking.

RING THICKNESS (T) - Total thickness of an edgewound retaining ring. It may be determined by multiplying the material thickness by the number of the turns and adding in the keystone value.

RIVER MARKS - A landmark feature of fatigue is River Marks which point in tdir ection of crack propagation.

RIVET - A headed metal fastener of malleable material used to join parts of structures and machines by inserting the shank through the aligned holes in each piece and forming a head on the headless end by upsetting.

RIVET NUT - A rivet nut, also known as a blind rivet nut or threaded insert. It is a one-piece internally threaded and counterbored tubular rivet that can be anchored entirely from one side. There are two types: one is designed to form a bulge on the back side of the panel as a screw is thightened in it threads. The other is similary drawn in using a screw, but is drawn into the sleve instead of creating a bulge.

RIVETING BURR - A small plain washer which is assembled with a small rivet before peening the end to provide a large area of contact on the part.

ROBERTSON - A type of driving recess that has a square-shaped indentation designed to accept a special power-tool bit or screwdriver.

ROBERTSON - Robertson also known as Square Drive, or Scrulox screw drive as specified by ANSI Type III. Robertson screwdrivers are easy to use one-handed, because the tapered socket tends to retain the screw, even if it is shaken. They also allow for the use of angled screw drivers and trim head screws. The socket-headed Robertson screws are self-centering, reduce cam-out, stop a power tool when set and can be removed if painted over or old and rusty. In industry, they speed up production and reduce product dame. The Robertson drive is available in 6 color-coded sizes. Screws are popular in woodworking and general construction.

ROCKWELL - A hardness scale while measures indentation hardness of metals. The hardness testing machine applies a major and a minor load to the material and then gives a direct indication of hardness.

ROCKWELL HARDNESS SCALE - Measures the indentation hardness of materials through the depth of penetration of an indenter, loaded on a material sample and compared to the penetration in some reference material. Its chief advantage is its ability to display hardness values directly, thus eliminating tedious calculations involved in other hardness measurements techniques. Also, the relatively simple and inexpensive set-up enables its installation in a variety of laboratories. It is typically used in engineering and metallurgy and is most common in the USA. Its commercial popularity arises from its speed, reliability, robustness, resolution and small area of indentation,

ROCKWELL HARDNESS TEST - A measure of hardness by determining the depth of penetration of a penetrator into the specimen under certain fixed conditions of test. The penetrator may be either a steel ball or a diamond sphero-conical penetrator. The hardness number is related to the depth of indentation and the higher the number the harder the material. Rockwell C Scale is used for harder materials, Rockwell B Scale for softer materials.

ROCKWELL HARDNESS TEST - An indentation hardness test based on the depth of penetration of a specified penetrator into the specimen under certain arbitrarily fixed conditions.

RoHS - Restriction of Hazardous Substances. Restricts the use of certain materials including lead, mercury, cadmium, hexavalent chromium, Polybrominated biphenyl ether (PBB), (PBDE) and DecaBDE.

ROLL MACHINES - Roll machines are machines that manufacturers use to roll internal screw threads. Typically, rolling machines consist of thread rolling die that presses into a blank. Thread rolling machines allow for large production runs.

ROLL OUT - The large diameter created by driving an undercut blade into the step of a stud during the thread rolling operation.

ROLL OVER - Term applied to the portion of a type R retainer opposite the shank end. Gets its name from the fact that during assembly this portion of the part is rolled over to captivate the insert.

ROLL THREADING - Applying a thread to a bolt or screw by rolling the piece between two grooved die plates, one of which is in motion, or between rotating grooved circular rolls.

ROLLED POINT - The point frequently produced by the cupping of the last 1 to 1 1/2 threads by the rolling pressure. This type of point is not produced intentionally but is considered as an alternative form of the plain sheared point.

ROLLED THREAD - A thread produced by the action of a form tool which when pressed into the surface of a blank displaces material radially.

ROLLED THREAD - A thread formed by plastically deforming a blank rather than by cutting. The majority of standard fasteners have their threads formed by rolling. Most threads are rolled before any heat treatment operation. Significant improvements in fatigue life can be achieved by rolling the thread after heat treatment, this improvement is due to compressive stresses being induced in the roots of the thread. However, because of the increased hardness of the bolt blank, the die life can be significantly reduced. Rolling thread also generally improves the surface finish which can have a beneficial effect on fatigue life.

ROOT - That surface of the thread which joins the flanks of adjacent thread forms and is identical with or immediately adjacent to the cylinder or cone from which the thread projects.

ROOT - 1. The smallest diameter created by driving an undercut blade into the step of a stud during the thread roll operation. 2.) That surface of the thread that joins the flanks of adjacent thread forms and is immediately adjacent to the base from which the thread projects. For exteranal thread the root is at the minor diameter. For internal thread the root is at the major diameter.

ROOT DIAMETER - The diameter from the bottom of the thread on one side, to the bottom of the thread on the other side, as known as the Minor Diameter.

ROOT TRUNCATION - The root truncation of a thread is the distance measured perpendicular to the axis, between the sharp root (or root apex) and the cylinder or cone which bounds the root.

ROTARY BROACHING - Rotary broaching is another common screw finishing process. Rotary broaching uses a saw-like cutting tool, called a rotary broach or wobble broach, to cut irregular shapes in metal.

ROTATIONAL CAPACITY TEST (ROCAP) - A test in which a bolt is assembled in a steel joint or tension measuring device with a lubricated nut, and tightened to not less than 10 percent of the bolt proof load. After initial tightening, the nut is rotated through specified degrees of rotation, and torque values are obtained to assure proper performance.

ROUND HEAD - Semi-elliptical top surface and flat bearing surface. General purpose head with high crown and deep recess but the diameter is smaller than a pan head. For general applications and where the requirement of a smaller head OD in application.

ROUNDNESS - Extent to which a feature is circular.

RPM - The speed at which the driver motor runs while the screw is installed. This is often adjustable using a variable pull trigger or different driver motor.

RTY - A product yield term meaning rolled through-put.

RUN OUT FLANGE - Feature on a formed part which is designated by the designer to absorb the tolerance accumulations created by multiple forming operations.

RUNOUT - A term frequently used interchangeably with eccentricity, but which normally refers to the amount which the outside surface of one component of a fastener runs out with respect to the outside surface or another component. As such it includes eccentricity, angularity, and bow. The amount of runout is usually expressed in terms of Total Indicator Reading (TIR).

RUST INHIBITORS - Oils, solvents, greases, etc. Vary in color and film thickness. Used to protect fasteners in transit and temporary storage.