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Allmetal Screw Products Category: General technical and industrial > Glossary of fastener terms Date & country: 14/08/2008, USA Words: 297

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).

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.

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
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.

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.

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.

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.

Tapped Hole
A threaded hole in a part.

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.

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.

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.

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, d...

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.