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A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. More screw threads are produced each year than any other machine element. [1]
Threads are generally produced according to one of the many standards of thread systems. Standards Development Organizations such as the American National Standards Institute, American Society of Mechanical Engineers, SAE International, International Organization for Standardization, Deutsches Institut für Normung (German Institute for Standardization), British Association and others produce these standards for manufacturers to follow when producing threaded components.
Standard | Name | Type | Example |
---|---|---|---|
ASME B1.1-2003 (R2018) | Unified Inch Screw Threads (UN and UNR Thread Form) | V Thread Form | 1⁄4″-20 UNC #4-40 UNC |
ASME B1.5-1997 (R2014) | Acme Screw Threads | Trapezoidal Thread Form | Tr 60×9 |
ANSI/ASME B1.9-1973 (R2017) | Buttress Inch Screw Threads | Breech-Lock Thread Form | |
ASME B1.10M-2004 (R2014) | Unified Miniature Screw Threads | V Thread Form | 0.60 UNM |
ANSI/ASME B1.11-1958 (R2016) | Microscope Objective Thread | V Thread Form | |
ASME B1.13M-2005 (R2015) | Metric Screw Threads: M Profile | V Thread Form | |
ASME B1.15-1995 (R2003) | Unified Inch Screw Threads (UNJ Thread Form) | V Thread Form | |
ASME B1.20.1-2013 | Pipe Threads, General Purpose (Inch) | Pipe Thread Form | |
ANSI B1.20.3-1976 (R2013) | Dryseal Pipe Threads (Inch) | Pipe Thread Form | |
ASME B1.20.7-1991 (R2013) | Hose Coupling Screw Threads - Inch | Pipe Thread Form | |
ASME B1.21M-1997 (R2013) | Metric Screw Threads - MJ Profile | V Thread Form | |
BS 34 | Tables of BS Whitworth, BS Fine and BS Pipe Threads | V Thread Form (55°) | 1⁄4″-20 BSW |
ISO 68-1:1998 | ISO general purpose screw threads—Basic profile—Part 1: Metric screw threads | V Thread Form | |
ISO 68-2:1998 | ISO general-purpose screw threads—Basic profile—Part 2: Inch screw threads | V Thread Form | |
ISO 261:1998 | ISO general purpose metric screw threads—General plan | V Thread Form | M6x1 |
ISO 262:1998 | ISO general purpose metric screw threads—Selected sizes for screws, bolts and nuts | V Thread Form | |
ISO 724:1993 | ISO general-purpose metric screw threads—Basic dimensions | V Thread Form | |
ISO 725:2009 | ISO inch screw threads—Basic dimensions | V Thread Form 51386 | |
DIN 40400 | Edison Thread | Round V Thread Form |
Standard | Name | Type | Obsolescence date |
---|---|---|---|
BS 93:1951 | British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A. | 1966 [2] | |
BS 93:2008 | British Association (B.A.) screw threads | 1966 [3] |
An international standard is a technical standard developed by one or more international standards organizations. International standards are available for consideration and use worldwide. The most prominent such organization is the International Organization for Standardization (ISO). Other prominent international standards organizations including the International Telecommunication Union (ITU) and the International Electrotechnical Commission (IEC). Together, these three organizations have formed the World Standards Cooperation alliance.
Standardization or standardisation is the process of implementing and developing technical standards based on the consensus of different parties that include firms, users, interest groups, standards organizations and governments. Standardization can help maximize compatibility, interoperability, safety, repeatability, or quality. It can also facilitate a normalization of formerly custom processes. In social sciences, including economics, the idea of standardization is close to the solution for a coordination problem, a situation in which all parties can realize mutual gains, but only by making mutually consistent decisions.
In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold that contains a negative impression of the intended shape. The metal is poured into the mold through a hollow channel called a sprue. The metal and mold are then cooled, and the metal part is extracted. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.
Taps and dies are tools used to create screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair. A die is used to cut or form the male portion of the mating pair. The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.
Hobbing is a machining process for gear cutting, cutting splines, and cutting sprockets on a hobbing machine, which is a special type of milling machine. The teeth or splines of the gear are progressively cut into the material by a series of cuts made by a cutting tool called a hob.
Broaching is a machining process that uses a toothed tool, called a broach, to remove material. There are two main types of broaching: linear and rotary. In linear broaching, which is the more common process, the broach is run linearly against a surface of the workpiece to produce the cut. Linear broaches are used in a broaching machine, which is also sometimes shortened to broach. In rotary broaching, the broach is rotated and pressed into the workpiece to cut an axisymmetric shape. A rotary broach is used in a lathe or screw machine. In both processes the cut is performed in one pass of the broach, which makes it very efficient.
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
A counterbore is a cylindrical flat-bottomed hole that enlarges another coaxial hole, or the tool used to create that feature. A counterbore hole is typically used when a fastener, such as a socket head cap screw or fillister head screw, is required to sit flush with or below the level of a workpiece's surface.
The weldability, also known as joinability, of a material refers to its ability to be welded. Many metals and thermoplastics can be welded, but some are easier to weld than others. A material's weldability is used to determine the welding process and to compare the final weld quality to other materials.
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basis for many other standards, such as BSF, BSP, BSCon, and BSCopper.
Gray iron, or grey cast iron, is a type of cast iron that has a graphitic microstructure. It is named after the gray color of the fracture it forms, which is due to the presence of graphite. It is the most common cast iron and the most widely used cast material based on weight.
Die cutting is the general process of using a die to shear webs of low-strength materials, such as rubber, fibre, foil, cloth, paper, corrugated fibreboard, chipboard, paperboard, plastics, pressure-sensitive adhesive tapes, foam, and sheet metal. In the metalworking and leather industries, the process is known as clicking and the machine may be referred to as a clicking machine. When a dinking die or dinking machine is used, the process is known as dinking. Commonly produced items using this process include gaskets, labels, tokens, corrugated boxes, and envelopes.
Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness. It comprises the small, local deviations of a surface from the perfectly flat ideal.
The ISO metric screw thread is the most commonly used type of general-purpose screw thread worldwide. They were one of the first international standards agreed when the International Organization for Standardization (ISO) was set up in 1947.
A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in a matching part.
In manufacturing, threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods ; deformative or transformative methods ; additive methods ; or combinations thereof.
In manufacturing, an undercut is a special type of recessed surface that is inaccessible using a straight tool. In turning, it refers to a recess in a diameter generally on the inside diameter of the part. In milling, it refers to a feature which is not visible when the part is viewed from the spindle. In molding, it refers to a feature that cannot be molded using only a single pull mold. In printed circuit board construction, it refers to the portion of the copper that is etched away under the photoresist.
A core is a device used in casting and moulding processes to produce internal cavities and reentrant angles. The core is normally a disposable item that is destroyed to get it out of the piece. They are most commonly used in sand casting, but are also used in die casting and injection moulding.
Surface integrity is the surface condition of a workpiece after being modified by a manufacturing process. The term was coined by Michael Field and John F. Kahles in 1964.
ISO 965 is an International Organization for Standardization (ISO) standard for metric screw thread tolerances. It specifies the basic profile for ISO general purpose metric screw threads (M) conforming to ISO 261.