AMS
Aeronautical Material Specifications are material and process
specifications
for aircraft components conforming to established engineering and
metallurgical practices
in the aircraft industries. They are developed by the SAE
aeronautics committee.
All specifications are prefixed by "AMS".
AN
Dimensional standards for aircraft fasteners developed by the
Aeronautical Standards
Group. All drawings are prefixed by "AN"
ASTM
Standards developed by the American Society for Testing and
Materials.
Acorn Die
A form of threading die for use in screw machines. The cutting
portion resembles an acorn.
Acorn Nut
A blind tapped hex nut with an acorn shaped top. Provides sealing
for projecting
threaded parts.
Age Hardening
A process of aging that increases hardness and strength, and
ordinarily decreases
ductility. Age hardening usually follows rapid cooling or cold
working.
Air Force & Navy Aeronautical Standard
Drawings
Dimensional standards for aircraft fasteners developed by the
Aeronautical
Standards Group . All drawings are prefixed by "AN" .
American Standards
Dimensional standards for fasteners, etc., developed by the
American Society of
Mechanical Engineers. (ASME)
Angle of Head
In countersunk heads, the included angles of the conical
underportion
or bearing surface, usually 82 or 100 degrees.
Balls
Used in "quick release pins" where permanent assemble and
disassemble
action tales place. Provides a reliable holding fastener.
Barrel Nut
An internally threaded screw having a slotted head.
Bent Bolt
A cylindrical rod having a thread at one end and the other end bent
to some desired conformation; also a bent cylindrical rod having
threads at both ends.
Bevel
A surface not at right angles to the rest of the piece.
Binding Head
Rounded top surface and slightly tapered sides. The bearing surface
is flat with annular
undercut optional.
Blind Rivet
A rivet designed for use where only one side of the work is
accessible.
Blunt Start
The removal of the partial thread at the entering end of thread.
Body of Bolt or Screw
Also designated grip. The blank portion of the bolt or screw which
is between the
thread and the head.
Bolt Blank
A headed rod or bar intended for a subsequent threading operation.
Bolt End
A headless rod threaded at one end and assembled with a square nut,
designed to be welded or otherwise fastened to a part or structure.
Brinell Hardness Test
A method of determining the hardness of metallic materials by
applying
a known load to the surface of the material through a hardened
steel ball
of known diameter. The diameter (or depth) of the resulting
impression
in the metal is measured. The Brinell hardness number is taken as
a
quotient of the applied load divided by the area of the surface
impression which is assumed to be spherical.
Broaching
A generating process whereby metal is removed with a multiple-point
tool,
usually a bar, with tooth height increasing from the starting end.
When
the broach is pulled or pushed through or over the work, each tooth
removes a clip of uniform thickness, in contrast to a milling
cutting
tooth which removes a wedge-shaped chip.
Button Die
Small adjustable dies for screw machines and similar work,
supported in
a ring holder.
Burnish
To smooth or polish by a rolling or sliding tool under pressure.
Cap Nut
A blind tapped hex nut with an acorn-shaped top. Provides sealing
for projecting thread parts.
Cap Screws
Term used to describe hexagon head, slotted head, square head and
socket head cap screws.
Captive Screws
Where the shank above the threaded portion is undercut lower than
the threaded portion.
Carbide
A compound of carbon with one or more matallic elements.
Carbide Tools
Tools with cutting points of tungsten, tantalum or other alloys of
sintered carbides.
Carbon Steel
Any steel made by combining carbon with iron.
Carriage Bolts
A round or flat head bolt with a square neck to prevent rotation.
Used in wood assemblies.
Case Harden
Hardening a ferrous alloy so that the outer portion or case is made
substantially harder than the inner portion or core. Typical
processes used for case hardening are carburizing, cyaniding,
carbonitriding, nitriding, induction hardening, and flame
hardening.
Casting
1. A term applied to the act of pouring molten metal into a mold.
2. The metal object produced by such pouring.
Castle Nut
A hexagon nut having a cylindrical portion at the end opposite to
the bearing face, with opposed slots in this portion which are
parallel to the axis, designed for insertion of a cotter to secure
the nut in place when used with a drilled fastener.
Centerless Grinding
Grinding the outside or inside diameter of a round piece not
mounted on centers.
Chamfer
(v) To bevel a sharp external edge. (n) A beveled edge.
Chasing Threads
Cutting screw threads by moving a tool along the axis of the work
to be threaded.
Chatter
Rough or unsatisfactory surfaces on work. It is usually caused by
a slight jumping of the tool away from the work or of the work away
from the tool.
Check Nut
A double chamfered hexagon machine screw nut Class 3B fit. (AN
316).
Chip
The metal removed by a tool.
Chuck
Device for holding work in machine tools.
Class of Thread
Class of threads are distringuished from each other by the amount
of tolerance or tolerance and allowance specified. Classes 1A, 2A,
and 3A apply to external threads, and Classes 1B, 2B and 3B apply
to internal threads.
Clevis
U-shaped shackle for connecting a rod to a pin.
Clevis Pins
A headed dowel pin with a drilled shank that accepts a cotter pin.
Used as a fastener where more than temporary holding actions is
required. (ASA B 5.20-1958).
Clinch Nut
A nut having a pilot which, after insertion in a hole, is clinched
or staked in place to prevent rotation.
Cold Heading
Forcing metal to flow cold into dies to form thicker sections and
more or less intricate shapes. The operation is performed in
specialized machines where the metal, in the form of a wire or bar
stock, may be upset or headed in certain sections to a larger size
and, if desired, may be extruded in other sections to a smaller
diameter than the stock wire.
Cold Swaging Process
A method of reducing or forming steel or other material while cold,
by drawing to a point or reducing the diameter, as may be required.
Cold Work
To deform metal stock by hammering, forming, drawing, etc., while
the metal is at ordinary room temperature.
Columbium
A metal which may be added to chrome-nickel stainless steel to
improve its welding and general heat-resistant qualities, by
preventing carbide precipitation.
Companion Flanges
Shaft attached collars of 18-8 stainless steel into which a
threaded piece may be joinedd. Has standard I.P.S. threads.
Comparator
A device for inspecting screw threads and outlines by comparing
them with a greatly enlarged standard chart.
Cone Point
A point in the form of a cone, commonly having an included angle of
90 degrees or 118 degrees when applied to set screws.
Copper Steel
When any minimum copper content is specified, the steel is classed
as copper steel. The copper is added to enhance errosion
resistance of the steel.
Corrosion
Gradual chemical or electrochemical attack on a metal by
atmosphere, moisture or other agents.
Cotter Pin
Used as a locking device in clevis pins, castellated nuts and
slotted nuts with drilled bolts. Ends available in various types
such as "extended mitre end", etc.
Counterbore
(v) To enlarge a hole to a given depth. (n) 1. The cylindrical
enlargement of the end of a drilled or bored hole. 2. A cutting
tool for counterboring, having a piloted end of the size of the
drilled hole.
Countersunk Head
A head, the underside of which is beveled to fit a flaring hole.
The bearing surface of other types of heads is generally
perpendicular to the body axis.
Crest
That surface of the thread which joins the flanks of the thread and
is farthest from the cylinder or cone from which the thread
projects.
Crest Clearance
As in a thread assembly, the distance, measured perpendicular to
the axis, between the crest of a thread and the root of its mating
thread.
Crest Truncation of Thread
The distance, measured perpendicular to the axis, between the sharp
root and the cylinder or cone which bounds the root.
Cup Point
A point in the form of a cone, commonly having an included angle of
90 degrees, with a conical depression in the end commonly having an
included angle of 118 degrees. The contact area is a circular
ridge which has considerable holding power with slight penetration,
applied to set screws generally.
Deburring
The removal of burrs by a secondary operation such as grinding.
Deep Drawing
Forming shapedd articles or shells by forcing sheet metal into a
die.
Die
1. One of a pair of hardened metal blocks for forming, impressing,
or cutting out a desired shape. 2. (thread). A tool for cutting
external threads. Opposite of tap.
Die Casting
A very accurate and smooth casting made by pouring a molten alloy
usually under pressure into a metal mold or die.
Die Chaser
The separate cutting tools used in die heads, which actually cut
the screw threads.
Dog Point
A cylindrical extension, or pilot, of diameter smaller than the
minor diameter of the thread, commonly equal to about D/2 in
length, with a conical section between it and the thread; usually
used as a pilot in assembling or as the end of a set screw
projecting into a fairly deep hole or slot.
Double End Stud
Threaded at both ends with standard Class 2A threads to take nut
assembly.
Dowel Pins
Used as a holding pin with chamfered on one end. Drilled headed
dowel pin (clevis pin) used - frequently removed fastener.
Dowel Screw
Both ends have Gimlet points, threaded similar to a Lag Bolt. The
center section has a plain unthreaded shoulder. Used in joining
two wooden members such as a leg to a table top.
Drill
(v) To sink a hole with a drill, usually with a twist drill. (n) A
pointed cuttiniig tool rotated under pressure.
Drilled Head or Shank
Used in AN Bolts and Machine Screws, etc.
Drive Screw
A piloted, multiple threaded screw with a large helix angle, used
for permanent applications. It forms a mating thread as it is
hammered or pressed into a prepared hole.
Driver Head
A head, on a bolt or screw, designed for driving the fastener by
means of a tool other than a wrench, such as a screw driver.
Drop Forging
Forming metal, usually under impact, by compression within dies
designed to produce the required shape.
Elevator Bolt
A flat, plain, circular countersunk head bolt with a square neck to
prevent rotation.
Endurance Limit
The maximum stress that a metal will withstand without failure
during a specified large number of cycles of stress.
Escutcheon Pin
A piece generally used to join a plate or shield, to cover or
protect softer or more delicate materials or actions.
Expansion Bolt
A combination of a "lag bolt" and an internally threaded split
sleeve, designed for fastening to stone or concrete by inserting a
sleeve into a hole in the concrete and expanding to a tight fit in
the hole by turning the lag both with a wrench.
Eyebolt
A bolt having a head in the form of an open or closed anchor ring,
or of a flattened and pierced section, with or without a collar or
shoulder under the head.
Face
To machine a flat surface perpendicular to the axis at rotation on
a lathe.
Fatigue Strength
The stress to which a metal can be subjected for a specified number
of cyclic changes of stress.
Feather Key
A parallel key fastened in either the shaft or in the hub of a
member sliding on it. When fastened in the shaft, it must be long
enough to hold or drive the sliding member in any of its positions
on the shaft. When in the sliding member the key need only be as
long as the hub.
Fillet
A rounded filling of the internal angle between two surfaces.
Fillister Head
Rounded top surface, cylindrical sides, and a flat bearing surface.
Fin
A thin projecting rib.
Finished Hexagon Bolts
A washer faced or chamfered bearing surface with a close body
tolerance.
Fin Neck Carriage Bolt
A plain, circular, oval head bolt with two oppositely located fins
to prevent rotation.
Fit
The general term used to signify the range of tightness which may
result from the application of a specific combination of allowances
and tolerances in the design of mating parts. See "Class of
Thread"
Flat Head
Flat top surface and a conical bearing surface.
Flex-Loc*
When used as a stop or lock nut, the locking threads of the slotted
top press inward against the bolt, lifting the nut upward and
causing the remaining threads to bear against the lower surface of
the bolt threads. (*TM)
Following Flank
The flank of a thread opposite to the leading flank.
Forge
To shape metal while holt and plastic by a hammering or forcing
process. Dies used in process.
Form of Thread
The profile of a thread in an axial plane for a length of one
pitch.
Free Machining
The property that makes machining easy because of the forming of
small chips, a characteristic imparted dto steel by sulfur, etc.
Full Annealing
Annealing a ferrous alloy by austenitizing and then cooling slowly
through the transformation range.
Full-Size Body
The body of a bolt or screw which has a diameter between the
minimum and maximum limits of the major diameter of the thread.
Galvanize
To treat with a bath of lead and zinc to prevent rusting
Gimlet Point
A taper-threaded point; applied to wood screws, Type A tapping
screws, lag bolts, etc.
Grind
To finish or polish a surface by means of an abrasive.
Grip
The unthreaded portion of a bolt or screw.
Half Dog Point
The same as a dog point but half as long; used on short screws for
the same purposes as the dog point, but in a shallower hole or
slot.
Hanger Bolt
One endd is gimlet pointed and has a wood screw thread. The other
end consists of a coarse machine screw thread. The center section
is unthreaded.
Hardenability
In a ferrous alloy, the property thaet determines the depth and
distribution of hardness induced by quenching.
Hardening
A method of heat treating metals by heating to a temperature
within, or above, the critical range, holding at that temperature
for a given time, and then cooling rapidly, usually by quenching in
oil or water.
Hardness
Resistance to plastic deformation by indentation, penetration,
scratching or bending.
Head
The preformed, enlarged end of a bolt, screw, pin, or rivet,
provided with a bearing surface which is usually either flat or
conical.
Header Point
A chamfer point, usually of 45 degrees included angle, forming by
a die at the time of heading and prior to threading.
Head Marking
Used to identify the material used in a fastener such as a bolt or
cap screw. The marking is either raised or indented to
specifications.
Heat Treating
An operation involving the heating and cooling of a metal to obtain
certain desirable conditions or properties.
Height of Thread
The distance, measured perpendicular to the axis, between the major
and minor cylinders or cones, respectively.
Heli-Coil
Coil of wire used as an insert to accept a screw or bolt and adding
holding power by forcing itself between the fastener and the walls
of the recess when the fastener is driven in.
Hexagonal
A recessed hexagon socket in the headd of a cap or set screw to add
greater tightening and loosening power. Used with a Hex key
wrench. (See Hexagon Head)
Hexagon Head
Flat top surface with hexagonal sides andn with a flat bearing
surface. (Six Sides)
Hook Bolt
A "bent bolt" having the unthreaded end bent to form a hook, such
as a round bend, square bend, right-angle bend, or acute-angle bend
hook bolt.
Hot Forming
Working operation such as bending and drawing sheet and plate,
forging, pressing, and heading, performed on metal heated to
temperatures above room temperature.
Immunize
To remove small particles of iron or grit from the surface of
stainless steel by pickling in an acid solution.
Impact Test
A test to determine the energy absorbed in fracturing a test bar at
high velocity. The test may be in tension or in bending, or it may
properly be a notch test if a notch is present, creating multiaxil
stresses.
Included Angle of Thread
The angle between the flanks or the thread measured in an axial
plane.
Incomplete Thread
On straight threads, that portion at the end having roots not fully
formed by the leadd or chamfer on threading toolss:
Ingot
Steel formerly in a molten state, transferred to an ingot mold to
solidify.
Interference Fit
A thread fit having limits of size so prescribed that an
interference always results when mating parts are assembled.
Internal Thread
A thread on the internal surface of a hollow cylinder or cone.
International Metric Thread System
A thread form similar to the American standard, excepting the depth
which is greater. There is a clearance between the root and mating
crest fixed at a maximum of 1/16 the height of the fundamental
triangle or 0.054 x pitch. A rounder root profile is recommended.
The angle in the plane of the axis is 60 degrees and the crest has
a flat like the American standard equal to 0.125 pitch.
Iron
Primarily the name of a metallic element. In the steel industry,
iron is the name of the product of a blast furnace containing 92 to
94 percent iron. Other names for blast furnace are pig iron and
hot metal.
J-Bolt
A "bent bolt" having the unthreaded end reverse bent to
approximately a semicircle.
Jackson Head
A machine screw with a small oval head. (Trimmed oval head).
Jam Nut
(1.) A second nut forced or jammed against the main nut to prevent
loosening. (2.) A thin nut.
Key
A small block or wedge inserted between shaft and hub to prevent
circumferential movement.
Keyslot
The recess cut for Woodruff keys produced by sinking a milling
cutter of the right diameter and width into a shaft.
Keyway
A groove or slot cut to fit a key. A key fits into a key seat and
slides into a keyway.
Knurl
A roughened surface produced by contact with a wheel which forces
metal above the surface while making indentations below the
surface.
Lag Bolt
A fastener having a square head, with a gimlet or cone point, and
a thin, sharp, coarse-pitch thread, designed for insertion in wood
or other resilient materials and producing its own mating thread.
Lead Error
A variation in the distance between the threads of a screw.
Left-Hand Thread
A thread is a left-hand thread, if, when viewied axially, it winds
in a counter-clockwise and receding direction. All left-hand
threads are designated LH.
Length of Fastener
The length of a flat bearing surface fastener is the distance, in
a line parallel to the axis, from the bearing surface to the
extreme point. The length of a countersunk head fastener is the
distance, in a line parallel to the axis, from the largest diameter
of the bearing surface to the extreme point.
Lentil Head Screw
Obsolete term for oval head screw.
Liquid Honing
A metal finishing process by forcing a stream of liquid, in which
a very fine abrasive is suspended, against the surface to be
finished.
Lock Nut
A nut which, in addition to serving the purposes of an ordinary
nut, has a special means for gripping a threaded member so that a
relative rotation between the nut and the threaded companion member
is prevented in use.
MS Specifications
(Military Standard)
Machineability
Relative ease or difficulty in forming.
Magnaflux
A magnetic method of determining surface and subsurface defects in
metals.
Major Diameter
On a straight thread, the diameter of the coaxial cylinder which
would pass through the crests of an external thread or the roots of
an internal thread.
Master Gage
A thread-plug gage which represents the physical dimensions of the
nominal or basic size of the part. It clearly establishes the
minimum size of the threaded hole and the maximum size of the screw
at the point at which interference between mating parts begin.
Maximum Material Limit
The maximum limit of size of an external dimension or the minimum
limit of size of an internal dimension.
Mechanical Properties
Those properties of a material that reveal the elastic and
inelastic reaction when force is applied, or that involve the
relationship between stress and strain; for example, the modulus of
elasticity, tensile strength and fatigue limit.
Micro-Inch
One millionth of an inch. Used in measuring imperfections of
surface finishes.
Milling Process
A machining process whereby a surface is generated with a rotating
toothed cutter. Each tooth takes an individual chip.
Minor Diameter
On a straight thread, the minor diameter is the diameter of the
coaxial cylinder which would pass through the roots of an external
thread.
Monel
A corrosion resisting metal consisting essentially of two-thirds
nickel and one-third copper.
NAS Drawings and Specifications
Dimensional and material standards for aircraft fasteners developed
by the National Aerospace Standards Committee. All drawings and
specifications are prefixed by "NAS".
Nail Point
A sharp pyramidal point of approximately 30 degrees or 45 degrees
included angle.
Naval Brass
A corrosion resisant metal containing 60 per cent copper, 39 1/4
per cent zinc and 3/4 per cent tin.
Neck
A portion reduced in diamter between the ends of a shaft.
Nickel
A silver-white metal usually used as an alloy in steel, bronze,
brass and cast iron. It tends to increase corrosion resistance.
Nipple
A short piece of threaded pipe used to connect two fittings.
Nifriding
A surface hardening process used on ferrous metals by heating the
metal in contact with ammonia gas or other nitrogenous material.
Non-Ferrous Metal
Metals or alloys without an appreciable amount of iron. Examples
are aluminum, brass, copper, etc.
Non-Magnetic
Steels with sufficient quantities of manganese or nickel to render
the steel non-magentic. 18-8 (300 series chrome-nickel steel) is
non-magnetic when annealed. Type 316 is non-magnetic in all
conditions. (See pg. 156 of the Data Book).
Normalize
To remove internal stresses by heatinig a metal piece to its
critical temperature and allowing it to cool very slowly.
Nut
A metal block (solid nut) or sleeve having an internal thread made
to assemble with the external thread on a bolt, screw, or other
threaded part. It may be a fastening means, an adjusting means, a
means for transmitting motion, or a means for transmitting power
with large mechanical advantage and nonreversible motion.
Nylon Fasteners
Fasteners made of a material that has a low dielectric constant and
relatively high tensile strength, enabling it to resist high
voltage at commercial frequencies. It can also operate at
continuous temperatures as high as 250 degrees F. Any temperatures
above has an effect to oxidize material. Electric and electronic
equipment manufacturers are finding many corrosion-resistant
applicables for this type of fastener.
One-Way Head Screw
A round head screw which is slotted but has side clearances at
diagonally opposite sides of the slot so that the screw can be
driven only in the direction of assembly, designed for preventing
tampering.
Open Washer
A washer with one side open so as to be removed or put under a nut
without removing the nut.
Oval Binding Head Screw
Obsolete term for a truss head screw.
Oval Head
Rounded top surface and a conical bearing surface with an included
angle usually of 82 degrees.
Oval Point
A rounded end which is used, particularly for set and adjusting
screws, to apply pressure without cutting action.
Oven Head Screw
Obsolete term for truss head screw.
Pan Head
Flat top surface rounded into cylindrical sides, and a flat bearing
surface. The recessed pan head has a rounded top surface blending
into cylindrical sides and a flat bearing surface.
Passivate
A process of surface treatment for neutralizing stainless steels.
A n oxydizing solution, such as nitric acid is applied to the
surface. This strengthens the normal protective film which helps
in resisting corrosion. It also removes any foreign substance
which might cause local corrosion.
Pattern Nuts
Special nuts usually furnished in plain or chamfered face unless
otherwise specified, and threads are unified Coarse or unified
Fine, Class 2B. (also small and extra small)
Peening
The stretching of metal by hammering or rolling the surface.
Phillips Recessed Head
A type of screw drive having a cross recess with a wide center
opening, steep walls and a blunt conical bottom. Permits easy and
rapid entrance of the 4-winged driver.
Physical Properties
Those properties familiarly diiscussed in physics, including those
descriabed under mechanical properties; for example, density,
electrical conductivity, co-efficient of thermal expansion.
Pinch Point
A sharp conical point, usually of 45 degrees included angle, formed
by a pinching operation.
Pipe Caps
A cap that threads onto a pipe (like a nut) to seal one end.
Pipe Fittings
The term applying to all forms of connecting parts which join
pieces sof pipe together.
Pipe Plugs
A short piece of threaded pipe, Slotted, Square Head or Socket,
used to close up one end of a fitting.
Pipe Screw Thread
American Standard pipe threads are tapered 1 inch in 16, or 3/4
inch per foot. They are 60 degree threads, of National form with
flat or rounded top and bottom.
Pitch
The distance, measured parallel to its axis, between corresponding
points on adjacent thread forms in the same axial plane and on the
same side of the axis.
Pitch Diameter
On a straight thread, the diameter of the coaxial cylinder, the
surface of which would pass through the thread profiles at such
points as to make the width of the groove equal to one-half of the
basic pitch. On a perfect thread this occurs at the point where
the widths of the thread and groove are equal.
Pitch Line
A generator of the cylinder or cone of a screw thread specified in
the definition of pitch diameter.
Plain Sheared Point
The end of a fastener cut approximately flat and square to the
axis, without chamfer.
Planer Head Bolt
A bolt havinig a large low square head, designed for insertion in
T-slots of planer, shaper, or milling machine tables.
Plate
The electro-chemical coating of a metal piece with a very different
metal.
Polish
To make smooth or lustrous by friction with a very fine abrasive.
Precipitation Hardening
Hardening caused by the precipitation of a constituent from a
supersaturated solid solution.
Precision Machine Screws
Slotted machine screws, milled from bar, cut thread, and are
machined finished Class 3A fits.
Process Annealing
Heating a ferrous alloy to a temperature close to, but below, the
lower limit of the transformation range and then cooling, in order
to soften the alloy for further cold working.
Punch
(v) To perforate by pressing a non-rotating tool through the work.
Quench Hardening
Hardening a ferrous alloy by austenitizing and then cooling rapidly
enough so that some or all of the austenite transforms to
martensite.
Quenching
Rapid cooling. When applicable, the following more specific terms
should be used: direct quenching, fog quenching, hot quenching,
interrupted quenching, selective quenching, spray quenching, and
time quenching.
Ream
To finish a drilled or punched hole very accurately with a rotating
lfuted tool of the required diameter.
Reamer
Tool used for englarging holes previously formed by drilling or
boring.
Recessed Head
A screw head, having specially formed indentations or recesses
centered on the head, into which a suitably formed driver fits.
Relief
The amount one plane surface of a piece is set below or above
another plane, usually for clearance or for economy in machining.
Ribbed Neck Carriage Bolt
A plain, circular, oval head bolt with a serrated neck to prevent
rotation.
Right-Hand Thread
A thread is a right hand thread if, when viewed axially, it winds
in a clockwise and receding direction.
Rivet
A headed metal fastener of some malleable material used to join
parts, as metal plates, of structures and machines by inserting the
shank through a hole in each piece and forming a head on the
headless end.
Rivet Bolt
A bolt designed as a substitute for rivets, having a button head,
a ribbed shank, a UNC thread, or a special thread such as a
Dardalet thread or Lok-Thread (TM).
Rockwell Hardness Test
A measure of hardness by determining the depth of penetration of a
pentrator into the specimen under certain fixed conditions of test.
The penetrator my 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.
Rod Ends
The ends of connecting rods which fit over crank pins or cross head
pins.
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 thread roling pressure. This type of point is not
produced intentionally but is considered as an alternative form of
the plain sheared point.
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.
Round Head
Semi-elliptical top surface and flat bearing surface.
SAE Specifications
Standards developed by the Society of Automotive Engineers, Inc.
SAE Standard Screw Threads
The SAE Screw Thread Standard, as revised in 1954, conforms with
the Unified and American Standard (ASA B1.1-1949).
Secondary Operations
Operations which include punching, shaving, trimming, drilling,
sawing, milling, pointing, tapping and polishing, etc., are
generally called secondary.
Self-Locking
Where binding action is self-induced on the body of the bolt, screw
or nut to keep it rigid and prevent movement and vibration.
Semi-Finished Hexagon Bolts
Bolts with standard sizes ranging from 1/4" through 4". Class 2A
tolerance. The bearing surface is washer faced.
Set Screw Points
A screw with various type points, cup, cone, flat, oval, half dog,
full dog, hanger or knurled, used to hold or "set" a collar on a
shaft or hold pieces of this kind against movement. Screws are
usually short, threaded entire length with the various type points
for different applications against this movement.
Screw Stock
Metal in the form of wire or rod, ordinarily a free-machininig type
of alloy, used for making screw machine products.
Screw Thread
A ridge of uniform section in the form of a helix on the external
or internal surface of a cone or frustum of a cone. A thread
formed on a cylinder is known as a straight or parallel thread, to
distinguish it from a taper thread which is formed on a cone of
frusetum of a cone.
Screw Thread Chasers
Cutting tools having teeth spaced to match the pitch of the threads
to be cut.
Set Screw
An externally threaded fastener with or without a head and having
a formed point, designed to prevent relative movement of parts when
screwed through one part upon or into another part.
Shear
To cut off sheet or bar metal between two blades.
Shear Nut
A fine threaded thin Castle or slotted nut.
Shear Strength
The stress required to produce fracture when impressed vertically
upon the cross-section of a material. Expressed in psi.
Shim
A thin spacer of sheet metal used for adjusting.
Shoulder Stud
A stud similar to a collar stud but having the plain portion of a
uniform diameter which is larger than the major diameter of the
thread, used where the design requirements do not permit the
separation of parts produced by a collar.
Single Thread
A single-start thread having lead equal to the pitch.
Sleeve Nut
A long nut with right or left threads for connecting two rods to
make an adjustable member.
Slip Washer
A washer with an opening large enough to slip the washer over a
bolt, and under the bold head. Also called a C washer.
Slotted Head
The head, of a bolt or screw, which has one or more slots across
the top to fit a screw driver.
Slotted Nut
A hexagon nut having opposed slots at the end opposite to the
bearing face which are perpendicular to the axis, designed for
insertion of a cotter to secure the nut in place when used wiht a
drilled fastener.
Slotted Pin
A pin that has a slot, either a square or round bottom, into which
an external clip or key is affixed in a locking position.
Socket Head
A recessed head in which the sides of the recess are parallel to
the body axis, into which a wrench fits. The recess is commonly
hexagonal or fluted in form. Also designated as "internal
wrenching head".
Spacers
Pieces designed to prevent crushing of sandwich-type and other
lightweight structural materials at fastening points. Sometimes
called inserts.
Spacers, Threaded
Spacers with threads through which a bolt can be put. This saves
weight by eliminating the nut and the reduction of the bolt length.
Spade Screws
A threaded, round body with a finger tightening projection.
(Regular Offset or Bent). Primarily used in places needed for
frequent adjustments or for knock-down assemblies.
Spanner Screws
Special unslotted screws surface, in Round undrilled, Flat drilled
and others, that require a special wrench.
Spanner Wrenches
Tools used to turn and tighten spanner screws.
Spin
To shape sheet metal by forcing it against a form as it revolves.
Spline
Raised portions of a shaft which fit into corresponding grooves in
a pulley or some sliding member. They can either permit end
movement or can be used as permanent fastening.
Spline Nut
A nut having external splines or ribs which hold it in place when
forced into a hole of slightly smaller diameter.
Spline Socket
A recessed socket in the head of a bolt or screw to develop greater
torque or driving ease without "round" the recess.
Split Rivet
A small rivet having a split end for securing by spreading the
ends.
Spot-Face
To finish a round spot on a rough surface, usually around a drilled
hole, to give a good seat to a screw or bolthead, cut, usually 1/16
inch deep.
Spring Lockwasher
A hardened coil wire having a slightly trapezoidal section after
forming which functions as a spring take-up device to compensate
for developed looseness and the loss of tension between the parts
of an assembly and to prevent the nut from turning.
Square Neck Carriage Bolt
A plain, truss or oval head bolt with a square neck to prevent
rotation.
Square Nuts
Nuts that are square rather than hexagonal.
Stainless
1. A trade name given to alloy steel that is corrosion and heat
resistant. The chief alloying elements are chromium, nickel and
silicon in various combinations with a possible small percentage of
titanium, vanadium, etc. 2. By AISI definition, a steel is called
"Stainless" when it contains 4 per cent or more chromium.
Stainless Steel
Any steel containing four or more per cent chromium is classified
as stainless.
Step Bolt
A plain, circular, oval head bolt with a square neck to prevent
rotation.
Stress Relieve
Heating to a suitable temperature, holding long enough to reduce
residual stresses and then colling to minimize the development of
new residual stresses.
Stripper Bolt
Discarded term for a shoulder screw.
Structure Machine Screws
A Flat Head Machine Screw (AN509C) with one included angle
approximately 100 degrees. Usually made in slotted and recessed
head types. With a "grip" or unthreaded body at the head.
Stud
A threaded rod. It may be threaded at both ends or continous.
Swage
To shape metal by hammering or pressure with the aid of a form or
anvil called a "swage block".
Tap
(v) To cut threads in a hole with a rotating tool called a "tap",
having threads on it and fluted to give cutting edges.
Tap Bolt
A fully threaded hexagon head bolt.
Tap End Stud
A double-end stud having each end threaded for a different class of
fit. The tap end has a Class 5 fit to produce an interference fit
in a tapped hole for semi-permanent assembly. The nut end is
threaded Class 2A for assembly with a standard nut.
Taper of Head
In flat bearing surface fasteners, the taper of a head or nut is
the angle between a side and the axis.
Tapped Hole
A threaded hole in a part.
Taper Pin
A pin that tapers from the larger end to a smaller end at the rate
of 1/4" per foot. The taper pin aids in hole alignment.
"Tee" Head Bolt
Bolt whose head slightly curves in the shape of a "T". Hence the
name "TEE" Head Bolt.
Tapping Screw
A screw which is threaded to the head and designed to form or tap
its mating thread in one or more of the parts to be assembled, of
various types as follows:
Tapping Screw, Type A
A thread-forming type of tapping screw having a gimlet point and a
thread of relatively coarse pitch and special form, used in
punched, or nested holes in metal sheets or in treated plywood or
special asbestos compositions.
Tapping Screw, Type B
Also designate "type Z". A thread-forming type of tapping screw,
having a blunt point with tapered threads of moderate pitch, used
with punched, drilled or nested holes.
Tapping Screw, Type C
A thread-forming type of tapping screw having a blunt point with
tapered threads at the end, having UNC or UNF threads and designed
for fastening metal sheets.
Tapping Screw, Type D
Also designated "type EC". A thread-cutting type of tapping screw
having the same thread as type C but provided with a fluted end
produced at thread rolling or a milled slot (or slots) produced
after thread rolling.
Tapping Screw, Type F
A thread-cutting type of tapping screw having the same thread form
as type C but provided with a multiple flute tapered end to
facilitate tapping.
Tapping Screw, Type FZ
A thread-cutting type of tapping screw having the same thread form
as type B but provided with a multiple fluted tapered end to
facilitate tapping.
Tapping Screw, Type G
Also designated "type EC". A thread-cutting type of tapping screw
having the same thread form as type C but provided with a slot
across the end to facilitate tapping in hard materials or deep
holes.
Tapping Screw, Type H
Also designated "type DB" or "type 25". A tapping screw having the
same thread as a type B but provided with a slot in the end to
facilitate tapping in plastics.
Tempering
Reheating a quench-hardened or normalized ferrous alloy to a
temperature below the transformation range and then cooling at any
rate desired.
Terminal Stud
A threadedd and collared pin having a plain cylindrical section,
used as a contact terminal on electrical appliances. Some types
are headed instead of collared
Thickness of Thread
The distance between the flanks of the thread measured at a
specified position and parallel to the axis.
Thread Milling
A machining process whereby thread is formed on a surface by
generating with a rotatiang toothed cutter. Each tooth takes an
individual chip.
Thread Rolling
A cold-forging process whereby screw threads are formed by
displacement of metal as opposed to cutting. The process is
usually used for producing external threads and is seldom practical
for small quantities.
Thread Series
Groups of diameter-pitch combinations distinguished from each other
by the number of threads per inch applied to a specific diameter.
Threaded Taper Pin
Dimensioned the same as a standard plain taper pin with the
addition of a threaded section usually at the small end. Used in
equipment where removal may be required.
Threads Per Inch
The reciprocal of the lead in inches.
Thumb Screw
A screw with a flattened or roughened head to be turned with thumb
and finger.
Tinners' Rivet
A small rivet having a head of the same form as a flat head rivet
but larger in diameter, used in sheet metal work.
Tolerance
The total permissible variation of a size. The tolerance is the
difference between the limits of size.
Tolerance Limit
The variation, positive or negative, by which a size is permitted
to depart from the design size.
Tooth Lockwasher
A washer, usually a thin disk with prongs or projections, which is
elastically deformed when assembled with a threaded fastener, so
that the prongs, on which the pressure is localized, resist
loosening of the fastener.
Total Thread
Includes the complete or effective thread and the incomplete
thread.
Trim Heads
Similar to the 82 degree flat and oval head machine screws except
that the size of head for a given size screw is one or two sizes
smaller than the regular flat and oval sizes.
Truss Head
Low rounded top surface with a flat bearing surface.
Tubular Rivet
A small rivet having a coaxial cylindrical hole in the headless
end, designed for securing by splaying the end.
Tumble
To clean, smooth, or polish in a rotating barrel or drum by
friction with each other, assisted by added mediums, as scraps,
balls, sawdust, etc.
Turn
To machine on a lathe.
Turnbuckle
A coupling, threaded right and left or swiveled on one end, for
adjustably connecting two rods.
U-Bolt
A "bent bolt" having threads at both ends of the rod and the rod
bent at the middle to a semicircle or to two right angles, used for
clamping.
Undercut Head
For short lengths of flat and oval head machine screws, the heads
are undercut to 70 per cent of normal side height to afford greater
length of thread on the screws.
Under-size Body
The reduced body of a bolt or screw, the diameter of which may
range from below the pitch diameter to the minimum major diameter
of the thread. Such a body diameter is found on some bolts or
screws having rolled threads.
Unified Thread Standards
The basic American standards for fastening screw threads as agreed
upon by standard bodies of Canada, the United Kingdom, and the
United States. They are a complete and integrated system of
threads for fastening purposes. Their outstanding characteristic
is general interchangeability of threads achieved through the
standardization of thread form, diameter-pitch combinations, and
limits of size.
Upsetting
1. A metal working operation similar to forging. 2. The process
of axial flow under axial compression of metal, as in forming heads
on rivets by flattening the end of wire.
Washer Face
A circular boss turned or otherwise produced on the bearing surface
of a bolt head or nut to relieve the corners.
Weld Screw
Projection welding applied to screws offer a means of providing
attached threated members in sheet metal construction. Welding
lugs on the head of the screw reduce the amount of current required
for surface welding and provide fusion of metal at predetermined
points.
Welding Stud
A "drive screw" having a flat fillister head, used as an anchorage
for welding.
Whitworth Thread
A screw thread, also known as the British Standard Whitworth
(B.S.W.), used principally in Great Britain.
Wing Nut
One-piece, round threaded nuts with wing lugs for ease of manual
assembly. Particularly suited to applications where frequent
removal and replacement or adjustment are required.
Wing Screws
Special screws with projection heads. Widely used in industry and
home where a finger tightened screw is needed for frequent
adjustments or for knock-down assembly applications. This piece is
produced by pressing, forming, machining, welding or die casting.
(Also available as 2 piece wing nut and studs, peened or welded
together.
Wood Screw
A metal screw having a driver head, a gimlet point, and a sharp-
crested, coarse pitch thread, for insertion in wood or resilient
materials. It produces its own mating thread.
Woodruff Key
A semi-circular or half-round piece, resting in a circular groove
cut in a shaft. Sometimes referred to as a half moon key. Largely
used in machine building.
Work Hardness
Hardness developed in metal as a result of cold working.
Wrench Head
A head on a fastener designed for driving or holding by means of an
externally applied wrench to the sides of the head.
Yield Point
The stress necessary to produce an elongation under load of 0.50
per cent of the specimen's original length. Expressed as psi.
Yield Strength
The stress at which a material exhibits a specified limiting set,
commonly taken by the offset method as 0.20 per cent of the
specimen's original length. Expressed as psi.