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97-596: The institution implemented to establish national standards (SLS) and to protect the rights of consumers in Sri Lanka. It serves as one of the consumer oriented organisations in Sri Lanka along with Consumer Affairs Authority (CAA) and Central Environmental Authority (CEA). Sri Lanka Standards Institution implemented Sri Lanka National Quality Award which is an annual award provided to identify Sri Lankan organisations that exhibited superior performances in improving quality by maintaining quality management and quality achievement. It

194-406: A wave . Another wave analogy is that pitch and TPI are inverses of each other in a similar way that period and frequency are inverses of each other. Coarse threads are those with larger pitch (fewer threads per axial distance), and fine threads are those with smaller pitch (more threads per axial distance). Coarse threads have a larger threadform relative to screw diameter, where fine threads have

291-745: A 55° thread angle and a thread depth of 0.640327 p and a radius of 0.137329 p , where p is the pitch. The thread pitch increased with diameter in steps specified on a chart. An example of the use of the Whitworth thread is the Royal Navy 's Crimean War gunboats. These were the first instance of "mass-production" techniques being applied to marine engineering. With the adoption of BSW by British railway lines, many of which had previously used their own standard both for threads and for bolt head and nut profiles, and improving manufacturing techniques, it came to dominate British manufacturing. American Unified Coarse

388-408: A bit more, yielding thread depths of 60% to 75% of the 0.65 p value. For example, a 75% thread sacrifices only a small amount of strength in exchange for a significant reduction in the force required to cut the thread. The result is that tap and die wear is reduced, the likelihood of breakage is lessened and higher cutting speeds can often be employed. This additional truncation is achieved by using

485-409: A bolt and a nut of the same pitch would fit together: the same requirement must separately be made for the minor and pitch diameters of the threads. Besides providing for a clearance between the crest of the bolt threads and the root of the nut threads, one must also ensure that the clearances are not so excessive as to cause the fasteners to fail. The minor diameter is the lower extreme diameter of

582-479: A cross-sectional view is taken in a plane containing the axis of the threads. For a screw, this is its outside diameter (OD). The major diameter of a nut cannot be directly measured (as it is obstructed by the threads themselves) but it may be tested with go/no-go gauges. The major diameter of external threads is normally smaller than the major diameter of the internal threads, if the threads are designed to fit together. But this requirement alone does not guarantee that

679-453: A direct result of the basic trigonometric functions . It is independent of measurement units (inch vs mm). However, UTS and ISO threads are not sharp threads. The major and minor diameters delimit truncations on either side of the sharp V. The nominal diameter of Metric (e.g. M8) and Unified (e.g. 5 ⁄ 16  in) threads is the theoretical major diameter of the male thread, which is truncated (diametrically) by 0.866 ⁄ 4 of

776-473: A flattened tip (in contrast to Whitworth's 55° angle and rounded tip). The 60° angle was already in common use in America, but Sellers's system promised to make it and all other details of threadform consistent. The Sellers thread, easier to produce, became an important standard in the U.S. during the late 1860s and early 1870s, when it was chosen as a standard for work done under U.S. government contracts, and it

873-404: A larger network and attracting more consumers to use the new technology, further enhancing network effects. Other benefits of standardization to consumers are reduced uncertainty, because consumers can be more certain that they are not choosing the wrong product, and reduced lock-in, because the standard makes it more likely that there will be competing products in the space. Consumers may also get

970-506: A liquid or paste pipe sealant such as pipe dope . The screw thread concept seems to have occurred first to Archimedes , who briefly wrote on spirals as well as designed several simple devices applying the screw principle. Leonardo da Vinci understood the screw principle, and left drawings showing how threads could be cut by machine. In the 1500s, screws appeared in German watches, and were used to fasten suits of armor. In 1569, Besson invented

1067-469: A looser fit than say an H2 tap. Metric uses D or DU limits which is the same system as imperial, but uses D or DU designators for over and undersized respectively, and goes by units of 0.013 mm (0.51 mils). Generally taps come in the range of H1 to H5 and rarely L1. The pitch diameter of a thread is measured where the radial cross section of a single thread equals half the pitch, for example: 16 pitch thread = 1 ⁄ 16   in = 0.0625   in

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1164-441: A measuring instrument or procedure is similar to every subjects or patients. For example, educational psychologist may adopt structured interview to systematically interview the people in concern. By delivering the same procedures, all subjects is evaluated using same criteria and minimising any confounding variable that reduce the validity . Some other example includes mental status examination and personality test . In

1261-501: A merger of two predecessor organizations (Bern and Paris treaties) that had similar objectives, but in more limited territories. With the advent of radiocommunication soon after the creation, the work of the ITU quickly expanded from the standardization of Telegraph communications, to developing standards for telecommunications in general. By the mid to late 19th century, efforts were being made to standardize electrical measurement. Lord Kelvin

1358-448: A metal fastening on the other side were usually fastened in non-threaded ways (such as clinching or upsetting against a washer). Maudslay standardized the screw threads used in his workshop and produced sets of taps and dies that would make nuts and bolts consistently to those standards, so that any bolt of the appropriate size would fit any nut of the same size. This was a major advance in workshop technology. Maudslay's work, as well as

1455-415: A particular thread, internal or external, is the diameter of a cylindrical surface, axially concentric to the thread, which intersects the thread flanks at equidistant points. When viewed in a cross-sectional plane containing the axis of the thread, the distance between these points being exactly one half the pitch distance. Equivalently, a line running parallel to the axis and a distance D 2 away from it,

1552-520: A practical commodity. During the next 40 years, standardization continued to occur on the intra- and inter-company levels. No doubt many mechanics of the era participated in this zeitgeist; Joseph Clement was one of those whom history has noted. In 1841, Joseph Whitworth created a design that, through its adoption by many British railway companies, became a standard for the United Kingdom and British Empire called British Standard Whitworth . During

1649-1012: A regional level (e.g. Europa, the Americas, Africa, etc) or at subregional level (e.g. Mercosur, Andean Community, South East Asia, South East Africa, etc), several Regional Standardization Organizations exist (see also Standards Organization ). The three regional standards organizations in Europe – European Standardization Organizations (ESOs), recognised by the EU Regulation on Standardization (Regulation (EU) 1025/2012) – are CEN , CENELEC and ETSI . CEN develops standards for numerous kinds of products, materials, services and processes. Some sectors covered by CEN include transport equipment and services, chemicals, construction, consumer products, defence and security, energy, food and feed, health and safety, healthcare, digital sector, machinery or services. The European Committee for Electrotechnical Standardization (CENELEC)

1746-507: A scientific basis, the robustness and applicability of a scientific basis, whether adoption of the certifications is voluntary, and the socioeconomic context (systems of governance and the economy ), with possibly most certifications being so far mostly largely ineffective. Moreover, standardized scientific frameworks can enable evaluation of levels of environmental protection, such as of marine protected areas , and serve as, potentially evolving, guides for improving, planning and monitoring

1843-508: A set of threads for watches. In particular applications and certain regions, threads other than the ISO metric screw threads remain commonly used, sometimes because of special application requirements, but mostly for reasons of backward compatibility : The first historically important intra-company standardization of screw threads began with Henry Maudslay around 1800, when the modern screw-cutting lathe made interchangeable V-thread machine screws

1940-445: A slightly larger tap drill in the case of female threads, or by slightly reducing the diameter of the threaded area of workpiece in the case of male threads, the latter effectively reducing the thread's major diameter . In the case of female threads, tap drill charts typically specify sizes that will produce an approximate 75% thread. A 60% thread may be appropriate in cases where high tensile loading will not be expected. In both cases,

2037-427: A smaller helix angle and allow finer adjustment. Finer threads develop greater preload with less tightening torque. There are three characteristic diameters ( ⌀ ) of threads: major diameter , minor diameter , and pitch diameter : Industry standards specify minimum (min.) and maximum (max.) limits for each of these, for all recognized thread sizes. The minimum limits for external (or bolt , in ISO terminology), and

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2134-502: A smaller threadform relative to screw diameter. This distinction is analogous to that between coarse teeth and fine teeth on a saw or file , or between coarse grit and fine grit on sandpaper . The common V-thread standards ( ISO 261 and Unified Thread Standard ) include a coarse pitch and a fine pitch for each major diameter. For example, 1 ⁄ 2 -13 belongs to the UNC series (Unified National Coarse) and 1 ⁄ 2 -20 belongs to

2231-571: A thread is often called its form or threadform (also spelled thread form ). It may be square , triangular , trapezoidal , or other shapes. The terms form and threadform sometimes refer to all design aspects taken together (cross-sectional shape, pitch, and diameters), but commonly refer to the standardized geometry used by the screw. Major categories of threads include machine threads, material threads, and power threads. Most triangular threadforms are based on an isosceles triangle . These are usually called V-threads or vee-threads because of

2328-520: A variety of benefits and drawbacks for firms and consumers participating in the market, and on technology and innovation. The primary effect of standardization on firms is that the basis of competition is shifted from integrated systems to individual components within the system. Prior to standardization a company's product must span the entire system because individual components from different competitors are incompatible, but after standardization each company can focus on providing an individual component of

2425-489: Is a Canadian Crown Corporation , DGN is a governmental agency within the Mexican Ministry of Economy, and ANSI and AENOR are a 501(c)(3) non-profit organization with members from both the private and public sectors. The determinants of whether an NSB for a particular economy is a public or private sector body may include the historical and traditional roles that the private sector fills in public affairs in that economy or

2522-432: 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 . The mechanical advantage of a screw thread depends on its lead , which is the linear distance the screw travels in one revolution. In most applications,

2619-449: Is a standard used for classifying the tolerance of the thread pitch diameter for taps . For imperial, H or L limits are used which designate how many units of 0.0005 inch over or undersized the pitch diameter is from its basic value, respectively. Thus a tap designated with an H limit of 3, denoted H3 , would have a pitch diameter 0.0005 × 3 = 0.0015 inch larger than base pitch diameter and would thus result in cutting an internal thread with

2716-415: Is called gender . Assembling a male-threaded fastener to a female-threaded one is called mating . The helix of a thread can twist in two possible directions, which is known as handedness . Most threads are oriented so that the threaded item, when seen from a point of view on the axis through the center of the helix, moves away from the viewer when it is turned in a clockwise direction, and moves towards

2813-416: Is codified in standards) for practical reasons—the thread-cutting or thread-forming tool cannot practically have a perfectly sharp point, and truncation is desirable anyway, because otherwise: In ball screws , the male-female pairs have bearing balls in between. Roller screws use conventional thread forms and threaded rollers instead of balls. The included angle characteristic of the cross-sectional shape

2910-439: Is less than caliper measurement of the male major diameter (outside diameter, OD). For example, tables of caliper measurements show 0.69 female ID and 0.75 male OD for the standards of "3/4 SAE J512" threads and "3/4-14 UNF JIS SAE-J514 ISO 8434-2". Note the female threads are identified by the corresponding male major diameter (3/4 inch), not by the actual measurement of the female threads. The pitch diameter (PD, or D 2 ) of

3007-651: Is likely the sole member from that economy in ISO. NSBs may be either public or private sector organizations, or combinations of the two. For example, the three NSBs of Canada, Mexico and the United States are respectively the Standards Council of Canada ( SCC ), the General Bureau of Standards ( Dirección General de Normas , DGN), and the American National Standards Institute (ANSI). SCC

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3104-573: Is not limited to the domain of electronic devices like smartphones and phone chargers but could also be applied to e.g. the energy infrastructure. Policy-makers could develop policies "fostering standard design and interfaces, and promoting the re-use of modules and components across plants to develop more sustainable energy infrastructure ". Computers and the Internet are some of the tools that could be used to increase practicability and reduce suboptimal results, detrimental standards and bureaucracy , which

3201-666: Is often associated with traditional processes and results of standardization. Taxes and subsidies, and funding of research and development could be used complementarily. Standardized measurement is used in monitoring, reporting and verification frameworks of environmental impacts, usually of companies, for example to prevent underreporting of greenhouse gas emissions by firms. In routine product testing and product analysis results can be reported using official or informal standards. It can be done to increase consumer protection , to ensure safety or healthiness or efficiency or performance or sustainability of products. It can be carried out by

3298-402: Is often called the thread angle . For most V-threads, this is standardized as 60 degrees , but any angle can be used. The cross section to measure this angle lies on a plane which includes the axis of the cylinder or cone on which the thread is produced. Lead ( / ˈ l iː d / ) and pitch are closely related concepts. They can be confused because they are the same for most screws. Lead

3395-660: Is organised and implemented by the Marketing and Promotion division of the Sri Lanka Standards Institution. Nestlé bagged the Sri Lanka National Quality Award from SLSI at the most recent 2017 Sri Lanka National Quality Awards ceremony. This standards - or measurement -related article is a stub . You can help Misplaced Pages by expanding it . Standardization Standardization ( American English ) or standardisation ( British English )

3492-451: Is provided by a class, but the maximum PD of the external thread is specified to be the same as the minimum PD of the internal thread, within specified tolerances, ensuring that the two can be assembled, with some looseness of fit still possible due to the margin of tolerance. A class called interference fit may even provide for negative allowances, where the PD of the screw is greater than the PD of

3589-669: Is the European Standardization organization developing standards in the electrotechnical area and corresponding to the International Electrotechnical Commission (IEC) in Europe. The first modern International Organization ( Intergovernmental Organization ) the International Telegraph Union (now International Telecommunication Union ) was created in 1865 to set international standards in order to connect national telegraph networks, as

3686-425: Is the distance along the screw's axis that is covered by one complete rotation of the screw thread (360°). Pitch is the distance from the crest of one thread to the next one at the same point. Because the vast majority of screw threadforms are single-start threadforms, their lead and pitch are the same. Single-start means that there is only one "ridge" wrapped around the cylinder of the screw's body. Each time that

3783-426: 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 ,

3880-677: The ISO metric screw threads (M) for most purposes, and BSP threads (R, G) for pipes. These were standardized by the International Organization for Standardization (ISO) in 1947. Although metric threads were mostly unified in 1898 by the International Congress for the standardization of screw threads, separate metric thread standards were used in France, Germany, and Japan, and the Swiss had

3977-402: The pitch diameter is not affected. The balancing of truncation versus thread strength is similar to many engineering decisions involving the strength, weight and cost of material, as well as the cost to machine it. Tapered threads are used on fasteners and pipe. A common example of a fastener with a tapered thread is a wood screw . The threaded pipes used in some plumbing installations for

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4074-520: The screw-cutting lathe , but the method did not gain traction and screws continued to be made largely by hand for another 150 years. In the 1800s, screw manufacturing began in England during the Industrial Revolution . In these times, there was no such thing as standardization. The bolts made by one manufacturer would not fit the nuts of another. Standardization of screw threads has evolved since

4171-543: The standard unit of electric current . R. E. B. Crompton became concerned by the large range of different standards and systems used by electrical engineering companies and scientists in the early 20th century. Many companies had entered the market in the 1890s and all chose their own settings for voltage , frequency , current and even the symbols used on circuit diagrams. Adjacent buildings would have totally incompatible electrical systems simply because they had been fitted out by different companies. Crompton could see

4268-524: The "PD line," slices the sharp-V form of the thread, having flanks coincident with the flanks of the thread under test, at exactly 50% of its height. We have assumed that the flanks have the proper shape, angle, and pitch for the specified thread standard. It is generally unrelated to the major ( D ) and minor ( D 1 ) diameters, especially if the crest and root truncations of the sharp-V form at these diameters are unknown. Everything else being ideal, D 2 , D , & D 1 , together, would fully describe

4365-565: The 1840s through 1860s, this standard was often used in the United States as well, in addition to myriad intra- and inter-company standards. In April 1864, William Sellers presented a paper to the Franklin Institute in Philadelphia , proposing a new standard to replace the US' poorly standardized screw thread practice. Sellers simplified the Whitworth design by adopting a thread profile of 60° and

4462-636: The National Standardizing Associations (ISA) was founded in 1926 with a broader remit to enhance international cooperation for all technical standards and specifications. The body was suspended in 1942 during World War II . After the war, ISA was approached by the recently formed United Nations Standards Coordinating Committee (UNSCC) with a proposal to form a new global standards body. In October 1946, ISA and UNSCC delegates from 25 countries met in London and agreed to join forces to create

4559-660: The Organization for the Advancement of Structured Information Standards ( OASIS ). There are many specifications that govern the operation and interaction of devices and software on the Internet , which do not use the term "standard" in their names. The W3C , for example, publishes "Recommendations", and the IETF publishes " Requests for Comments " (RFCs). Nevertheless, these publications are often referred to as "standards", because they are

4656-474: The UNF series (Unified National Fine). Similarly, M10 (10 mm nominal outer diameter) as per ISO 261 has a coarse thread version at 1.5 mm pitch and a fine thread version at 1.25 mm pitch. The term coarse here does not mean lower quality, nor does the term fine imply higher quality. The terms when used in reference to screw thread pitch have nothing to do with the tolerances used (degree of precision) or

4753-466: The amount of craftsmanship, quality, or cost. They simply refer to the size of the threads relative to the screw diameter. Coarse threads are more resistant to stripping and cross threading because they have greater flank engagement. Coarse threads install much faster as they require fewer turns per unit length. Finer threads are stronger as they have a larger stress area for the same diameter thread. Fine threads are less likely to vibrate loose as they have

4850-471: The benefit of being able to mix and match components of a system to align with their specific preferences. Once these initial benefits of standardization are realized, further benefits that accrue to consumers as a result of using the standard are driven mostly by the quality of the technologies underlying that standard. Screw thread A screw thread is a helical structure used to convert between rotational and linear movement or force. A screw thread

4947-433: The commercial interest of Indus merchants as smaller weight measures were used to measure luxury goods while larger weights were employed for buying bulkier items, such as food grains etc. Weights existed in multiples of a standard weight and in categories. Technical standardisation enabled gauging devices to be effectively used in angular measurement and measurement for construction. Uniform units of length were used in

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5044-479: The context of customer service , standardization refers to the process of developing an international standard that enables organizations to focus on customer service, while at the same time providing recognition of success through a third party organization, such as the British Standards Institution . An international standard has been developed by The International Customer Service Institute . In

5141-635: The context of supply chain management and materials management , standardization covers the process of specification and use of any item the company must buy in or make, allowable substitutions, and build or buy decisions. The process of standardization can itself be standardized. There are at least four levels of standardization: compatibility, interchangeability , commonality and reference . These standardization processes create compatibility, similarity, measurement, and symbol standards. There are typically four different techniques for standardization Types of standardization process: Standardization has

5238-648: The context of information exchange, standardization refers to the process of developing standards for specific business processes using specific formal languages . These standards are usually developed in voluntary consensus standards bodies such as the United Nations Center for Trade Facilitation and Electronic Business ( UN/CEFACT ), the World Wide Web Consortium ( W3C ), the Telecommunications Industry Association (TIA), and

5335-550: The context of social criticism and social science , standardization often means the process of establishing standards of various kinds and improving efficiency to handle people, their interactions, cases, and so forth. Examples include formalization of judicial procedure in court, and establishing uniform criteria for diagnosing mental disease. Standardization in this sense is often discussed along with (or synonymously to) such large-scale social changes as modernization, bureaucratization, homogenization, and centralization of society. In

5432-515: The contributions of other engineers, accomplished a modest amount of industry standardization; some companies' in-house standards spread a bit within their industries. Joseph Whitworth 's screw thread measurements were adopted as the first (unofficial) national standard by companies around the country in 1841. It came to be known as the British Standard Whitworth , and was widely adopted in other countries. This new standard specified

5529-689: The country, and enabled the markets to act more rationally and efficiently, with an increased level of cooperation. After the First World War , similar national bodies were established in other countries. The Deutsches Institut für Normung was set up in Germany in 1917, followed by its counterparts, the American National Standard Institute and the French Commission Permanente de Standardisation , both in 1918. At

5626-409: The crest or root), but instead are truncated, yielding a final thread depth that can be expressed as a fraction of the pitch value. The UTS and ISO standards codify the amount of truncation, including tolerance ranges. A perfectly sharp 60° V-thread will have a depth of thread ("height" from root to crest) equal to 0.866 of the pitch. This fact is intrinsic to the geometry of an equilateral triangle —

5723-444: The delivery of fluids under pressure have a threaded section that is slightly conical . Examples are the NPT and BSP series. The seal provided by a threaded pipe joint is created when a tapered externally threaded end is tightened into an end with internal threads. For most pipe joints, a good seal requires the application of a separate sealant into the joint, such as thread seal tape , or

5820-420: The development stage of that economy. Standards can be: The existence of a published standard does not necessarily imply that it is useful or correct. Just because an item is stamped with a standard number does not, by itself, indicate that the item is fit for any particular use. The people who use the item or service (engineers, trade unions, etc.) or specify it (building codes, government, industry, etc.) have

5917-667: The early nineteenth century to facilitate compatibility between different manufacturers and users. The standardization process is still ongoing; in particular there are still (otherwise identical) competing metric and inch-sized thread standards widely used. Standard threads are commonly identified by short letter codes (M, UNC, etc.) which also form the prefix of the standardized designations of individual threads. Additional product standards identify preferred thread sizes for screws and nuts, as well as corresponding bolt head and nut sizes, to facilitate compatibility between spanners (wrenches) and other tools. The most common threads in use are

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6014-574: The galling of the threads. For this reason, some allowance , or minimum difference, between the PDs of the internal and external threads has to generally be provided for, to eliminate the possibility of deviations from the ideal thread form causing interference and to expedite hand assembly up to the length of engagement. Such allowances, or fundamental deviations , as ISO standards call them, are provided for in various degrees in corresponding classes of fit for ranges of thread sizes. At one extreme, no allowance

6111-485: 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. Divergent national standards impose costs on consumers and can be a form of non-tariff trade barrier . Standard weights and measures were developed by the Indus Valley civilization . The centralized weight and measure system served

6208-471: The international level . Standardization is also used to ensure safe design and operation of laboratories and similar potentially dangerous workplaces, e.g. to ensure biosafety levels . There is research into microbiology safety standards used in clinical and research laboratories. In the context of defense, standardization has been defined by NATO as The development and implementation of concepts, doctrines, procedures and designs to achieve and maintain

6305-606: The lack of efficiency in this system and began to consider proposals for an international standard for electric engineering. In 1904, Crompton represented Britain at the International Electrical Congress , held in connection with Louisiana Purchase Exposition in Saint Louis as part of a delegation by the Institute of Electrical Engineers . He presented a paper on standardisation, which was so well received that he

6402-545: The lead of a screw thread is chosen so that friction is sufficient to prevent linear motion being converted to rotary, that is so the screw does not slip even when linear force is applied, as long as no external rotational force is present. This characteristic is essential to the vast majority of its uses. The tightening of a fastener's screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight elastic deformation . Screw threads have several applications: In all of these applications,

6499-645: The manufacturer, an independent laboratory, a government agency, a magazine or others on a voluntary or commissioned/mandated basis. Estimating the environmental impacts of food products in a standardized way – as has been done with a dataset of >57,000 food products in supermarkets – could e.g. be used to inform consumers or in policy . For example, such may be useful for approaches using personal carbon allowances (or similar quota) or for targeted alteration of (ultimate overall) costs . Public information symbols (e.g. hazard symbols ), especially when related to safety, are often standardized, sometimes on

6596-401: The maximum limits for internal ( nut ), thread sizes are there to ensure that threads do not strip at the tensile strength limits for the parent material. The minimum limits for internal, and maximum limits for external, threads are there to ensure that the threads fit together. The major diameter of threads is the larger of two extreme diameters delimiting the height of the thread profile, as

6693-477: The new International Organization for Standardization (ISO); the new organization officially began operations in February ;1947. In general, each country or economy has a single recognized National Standards Body (NSB). Examples include ABNT , AENOR (now called UNE, Spanish Association for Standardization ) , AFNOR , ANSI , BSI , DGN , DIN , IRAM , JISC , KATS , SABS , SAC , SCC , SIS . An NSB

6790-468: The number of starts, very often has a value of 1, in which case their relationship becomes equality. In general, lead is equal to pitch times the number of starts. Whereas metric threads are usually defined by their pitch, that is, how much distance per thread, inch-based standards usually use the reverse logic, that is, how many threads occur per a given distance. Thus, inch-based threads are defined in terms of threads per inch (TPI). Pitch and TPI describe

6887-619: The nut by at least the amount of the allowance. The pitch diameter of external threads is measured by various methods: The way in which male and female fit together, including play and friction, is classified (categorized) in thread standards. Achieving a certain class of fit requires the ability to work within tolerance ranges for dimension (size) and surface finish . Defining and achieving classes of fit are important for interchangeability . Classes include 1, 2, 3 (loose to tight); A (external) and B (internal); and various systems such as H and D limits. Thread limit or pitch diameter limit

6984-682: The onset of the Industrial Revolution and the need for high-precision machine tools and interchangeable parts . Henry Maudslay developed the first industrially practical screw-cutting lathe in 1800. This allowed for the standardization of screw thread sizes for the first time and paved the way for the practical application of interchangeability (an idea that was already taking hold) to nuts and bolts . Before this, screw threads were usually made by chipping and filing (that is, with skilled freehand use of chisels and files ). Nuts were rare; metal screws, when made at all, were usually for use in wood. Metal bolts passing through wood framing to

7081-509: The opposing threads, and everything else is ideal, if the pitch diameters of a screw and nut are exactly matched, there should be no play at all between the two as assembled, even in the presence of positive root-crest clearances. This is the case when the flanks of the threads come into intimate contact with one another, before the roots and crests do, if at all. However, this ideal condition would in practice only be approximated and would generally require wrench-assisted assembly, possibly causing

7178-437: The pitch actual pitch diameter of the thread is measured at the radial cross section measures 0.03125   in. To achieve a predictably successful mating of male and female threads and assured interchangeability between males and between females, standards for form, size, and finish must exist and be followed. Standardization of threads is discussed below. Screw threads are almost never made perfectly sharp (no truncation at

7275-431: The pitch from the dimension over the tips of the "fundamental" (sharp cornered) triangles. The resulting flats on the crests of the male thread are theoretically one eighth of the pitch wide (expressed with the notation 1 ⁄ 8 p or 0.125 p ), although the actual geometry definition has more variables than that. A full (100%) UTS or ISO thread has a height of around 0.65 p . Threads can be (and often are) truncated

7372-656: The planning of towns such as Lothal , Surkotada , Kalibangan , Dolavira , Harappa , and Mohenjo-daro . The weights and measures of the Indus civilization also reached Persia and Central Asia , where they were further modified. Shigeo Iwata describes the excavated weights unearthed from the Indus civilization: A total of 558 weights were excavated from Mohenjodaro, Harappa, and Chanhu-daro , not including defective weights. They did not find statistically significant differences between weights that were excavated from five different layers, each measuring about 1.5 m in depth. This

7469-497: The products of regular standardization processes. Standardized product certifications such as of organic food , buildings or possibly sustainable seafood as well as standardized product safety evaluation and dis/approval procedures (e.g. regulation of chemicals , cosmetics and food safety ) can protect the environment. This effect may depend on associated modified consumer choices , strategic product support/obstruction, requirements and bans as well as their accordance with

7566-457: The protection-quality, -scopes and -extents. Moreover, technical standards could decrease electronic waste and reduce resource-needs such as by thereby requiring (or enabling) products to be interoperable , compatible (with other products, infrastructures, environments, etc), durable , energy-efficient , modular , upgradeable / repairable and recyclable and conform to versatile, optimal standards and protocols. Such standardization

7663-627: The required levels of compatibility , interchangeability or commonality in the operational, procedural, material, technical and administrative fields to attain interoperability. In some cases, standards are being used in the design and operation of workplaces and products that can impact consumers' health. Some of such standards seek to ensure occupational safety and health and ergonomics . For example, chairs (see e.g. active sitting and steps of research ) could be potentially be designed and chosen using standards that may or may not be based on adequate scientific data. Standards could reduce

7760-591: The responsibility to consider the available standards, specify the correct one, enforce compliance, and use the item correctly: validation and verification . To avoid the proliferation of industry standards, also referred to as private standards , regulators in the United States are instructed by their government offices to adopt "voluntary consensus standards" before relying upon "industry standards" or developing "government standards". Regulatory authorities can reference voluntary consensus standards to translate internationally accepted criteria into public policy . In

7857-415: The same underlying physical property—merely in different terms. When the inch is used as the unit of measurement for pitch, TPI is the reciprocal of pitch and vice versa. For example, a 1 ⁄ 4 -20 thread has 20 TPI, which means that its pitch is 1 ⁄ 20 inch (0.050 in or 1.27 mm). As the distance from the crest of one thread to the next, pitch can be compared to the wavelength of

7954-408: The screw thread has two main functions: Every matched pair of threads, external and internal , can be described as male and female . Generally speaking, the threads on an external surface are considered male, while the ones on an internal surface are considered female. For example, a screw has male threads, while its matching hole (whether in nut or substrate) has female threads. This property

8051-418: The screw's body rotates one turn (360°), it has advanced axially by the width of one ridge. "Double-start" means that there are two "ridges" wrapped around the cylinder of the screw's body. Each time that the screw's body rotates one turn (360°), it has advanced axially by the width of two ridges. Another way to express this is that lead and pitch are parametrically related, and the parameter that relates them,

8148-419: The shape of the letter V . For 60° V-threads, the isosceles triangle is, more specifically, equilateral . For buttress threads , the triangle is scalene . The theoretical triangle is usually truncated to varying degrees (that is, the tip of the triangle is cut short). A V-thread in which there is no truncation (or a minuscule amount considered negligible) is called a sharp V-thread . Truncation occurs (and

8245-587: The size and weight of a girder to employ for given work." The Engineering Standards Committee was established in London in 1901 as the world's first national standards body. It subsequently extended its standardization work and became the British Engineering Standards Association in 1918, adopting the name British Standards Institution in 1931 after receiving its Royal Charter in 1929. The national standards were adopted universally throughout

8342-465: The system. When the shift toward competition based on individual components takes place, firms selling tightly integrated systems must quickly shift to a modular approach, supplying other companies with subsystems or components. Standardization has a variety of benefits for consumers, but one of the greatest benefits is enhanced network effects. Standards increase compatibility and interoperability between products, allowing information to be shared within

8439-399: The thread form. Knowledge of PD determines the position of the sharp-V thread form, the sides of which coincide with the straight sides of the thread flanks: e.g., the crest of the external thread would truncate these sides a radial displacement D  −  D 2 away from the position of the PD line. Provided that there are moderate non-negative clearances between the root and crest of

8536-615: The thread. Major diameter minus minor diameter, divided by two, equals the height of the thread. The minor diameter of a nut is its inside diameter. The minor diameter of a bolt can be measured with go/no-go gauges or, directly, with an optical comparator . As shown in the figure at right, threads of equal pitch and angle that have matching minor diameters, with differing major and pitch diameters, may appear to fit snugly, but only do so radially; threads that have only major diameters matching (not shown) could also be visualized as not allowing radial movement. The reduced material condition , due to

8633-406: The unused spaces between the threads, must be minimized so as not to overly weaken the fasteners. In order to fit a male thread into the corresponding female thread, the female major and minor diameters must be slightly larger than the male major and minor diameters. However this excess does not usually appear in tables of sizes. Calipers measure the female minor diameter (inside diameter, ID), which

8730-411: The variety of products and lead to convergence on fewer broad designs – which can often be efficiently mass-produced via common shared automated procedures and instruments – or formulations deemed to be the most healthy, most efficient or best compromise between healthiness and other factors. Standardization is sometimes or could also be used to ensure or increase or enable consumer health protection beyond

8827-450: The viewer when it is turned counterclockwise. This is known as a right-handed ( RH ) thread, because it follows the right-hand grip rule . Threads oriented in the opposite direction are known as left-handed ( LH ). By common convention, right-handedness is the default handedness for screw threads. Therefore, most threaded parts and fasteners have right-handed threads. Left-handed thread applications include: The cross-sectional shape of

8924-420: The workplace and ergonomics such as standards in food, food production, hygiene products, tab water, cosmetics, drugs/medicine, drink and dietary supplements, especially in cases where there is robust scientific data that suggests detrimental impacts on health (e.g. of ingredients) despite being substitutable and not necessarily of consumer interest. In the context of assessment, standardization may define how

9021-596: Was also adopted as a standard by highly influential railroad industry corporations such as the Baldwin Locomotive Works and the Pennsylvania Railroad . Other firms adopted it, and it soon became a national standard for the U.S., later becoming generally known as the United States Standard thread (USS thread). Over the next 30 years the standard was further defined and extended and evolved into

9118-460: Was an important figure in this process, introducing accurate methods and apparatus for measuring electricity. In 1857, he introduced a series of effective instruments, including the quadrant electrometer, which cover the entire field of electrostatic measurement. He invented the current balance , also known as the Kelvin balance or Ampere balance ( SiC ), for the precise specification of the ampere ,

9215-529: Was asked to look into the formation of a commission to oversee the process. By 1906 his work was complete and he drew up a permanent constitution for the International Electrotechnical Commission . The body held its first meeting that year in London, with representatives from 14 countries. In honour of his contribution to electrical standardisation, Lord Kelvin was elected as the body's first President. The International Federation of

9312-405: Was evidence that strong control existed for at least a 500-year period. The 13.7-g weight seems to be one of the units used in the Indus valley. The notation was based on the binary and decimal systems. 83% of the weights which were excavated from the above three cities were cubic, and 68% were made of chert . The implementation of standards in industry and commerce became highly important with

9409-881: Was originally based on almost the same imperial fractions. The Unified thread angle is 60° and has flattened crests (Whitworth crests are rounded). Thread pitch is the same in both systems except that the thread pitch for the 1 ⁄ 2  in. (inch) bolt is 12 threads per inch (tpi) in BSW versus 13 tpi in the UNC. By the end of the 19th century, differences in standards between companies were making trade increasingly difficult and strained. For instance, an iron and steel dealer recorded his displeasure in The Times : "Architects and engineers generally specify such unnecessarily diverse types of sectional material or given work that anything like economical and continuous manufacture becomes impossible. In this country no two professional men are agreed upon

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