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45-528: Abraham Ferwerda was a printer and publisher in Leeuwarden, who first published the Leeuwarder Courant on 29 July 1752, and reportedly made a fortune publishing his paper. From the beginning, the intention was to produce a politically neutral paper which would gain revenue from objectively reporting news; until well into the nineteenth century the paper maintained its rather bland image. A conscious choice

90-412: A l ≡ F o u t F i n = 2 π r l {\displaystyle \mathrm {MA} _{ideal}\equiv {\frac {F_{out}}{F_{in}}}={\frac {2\pi r}{l}}\,} It can be seen that the mechanical advantage of a screw depends on its lead, l {\displaystyle l\,} . The smaller the distance between its threads,

135-404: A lever , if the force on the load end is too large it will move backwards, doing work on the applied force. Most screws are designed to be self-locking, and in the absence of torque on the shaft will stay at whatever position they are left. However, some screw mechanisms with a large enough pitch and good lubrication are not self-locking and will overhaul, and a very few, such as a push drill , use

180-445: A heavy wooden frame with a screw mechanism , enabling the even application of pressure to inked type and paper. Gutenberg's printing press accelerated the production of books, leading to the spread of knowledge and the democratization of information. In the following centuries, printing presses underwent significant advancements. In the 18th century, the steam-powered press was introduced, enabling higher print volumes. Subsequently,

225-439: A large 60° thread angle: In machine linkages such as lead screws or jackscrews , in contrast, friction must be minimized. Therefore, threads with smaller angles are used: The screw propeller , although it shares the name screw , works on very different physical principles from the above types of screw, and the information in this article is not applicable to it. The linear distance d {\displaystyle d\,}

270-465: A load in motion", defined it as an inclined plane wrapped around a cylinder, and described its fabrication and uses, including describing a tap for cutting female screw threads. Because their complicated helical shape had to be laboriously cut by hand, screws were only used as linkages in a few machines in the ancient world. Screw fasteners only began to be used in the 15th century in clocks, after screw-cutting lathes were developed. The screw

315-408: A point on the edge of the shaft moves to the linear distance d out the shaft moves. If r is the radius of the shaft, in one turn a point on the screw's rim moves a distance of 2π r , while its shaft moves linearly by the lead distance l . So the distance ratio is The mechanical advantage MA of a screw is defined as the ratio of axial output force F out applied by the shaft on a load to

360-411: A rubber blanket, which, in turn, printed the image onto the paper. Offset lithography offered more efficient and cost-effective printing, enabling high-quality reproductions and color printing on a large scale. Printers can include: Screw (simple machine) The screw is a mechanism that converts rotational motion to linear motion , and a torque (rotational force) to a linear force . It

405-458: A screw can amplify force; a small rotational force ( torque ) on the shaft can exert a large axial force on a load. The smaller the pitch (the distance between the screw's threads), the greater the mechanical advantage (the ratio of output to input force). Screws are widely used in threaded fasteners to hold objects together, and in devices such as screw tops for containers, vises , screw jacks and screw presses . Other mechanisms that use

450-421: A screw shaft moves when it is rotated through an angle of α {\displaystyle \alpha \,} degrees is: where l {\displaystyle l\,} is the lead of the screw. The distance ratio of a simple machine is defined as the ratio of the distance the applied force moves to the distance the load moves. For a screw it is the ratio of the circular distance d in

495-409: A screw's thread can twist in two possible directions, which is known as handedness . Most screw threads are oriented so that when seen from above, the screw shaft moves away from the viewer (the screw is tightened) when turned in a clockwise direction. This is known as a right-handed ( RH ) thread, because it follows the right hand grip rule : when the fingers of the right hand are curled around

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540-415: A single helical thread wrapped around them, the lead and pitch are equal. They only differ in " multiple start " screws, which have several intertwined threads. In these screws the lead is equal to the pitch multiplied by the number of starts . Multiple-start screws are used when a large linear motion for a given rotation is desired, for example in screw caps on bottles, and ball point pens . The helix of

585-425: A torque to the shaft will cause it to turn, but no amount of axial load force against the shaft will cause it to turn back the other way, even if the applied torque is zero. This is in contrast to some other simple machines which are " reciprocal " or " non locking " which means if the load force is great enough they will move backwards or " overhaul ". Thus, the machine can be used in either direction. For example, in

630-423: Is W i n = 2 π r F i n {\displaystyle W_{in}=2\pi rF_{in}\,} and the work done on the load is W o u t = l F o u t {\displaystyle W_{out}=lF_{out}\,} . So the ideal mechanical advantage of a screw is equal to the distance ratio : M A i d e

675-731: Is a dimensionless number between 0 and 1 defined as the ratio of output work to input work Work is defined as the force multiplied by the distance moved, so W i n = F i n d i n {\displaystyle W_{in}=F_{in}d_{in}\,} and W o u t = F o u t d o u t {\displaystyle W_{out}=F_{out}d_{out}\,} and therefore M A = F o u t F i n = η 2 π r l {\displaystyle MA={\frac {F_{out}}{F_{in}}}=\eta {\frac {2\pi r}{l}}\,} or in terms of torque So

720-512: Is considered to have introduced the screw in Ancient Greece. By the first century BC, the screw was used in the form of the screw press and the Archimedes' screw. Greek philosophers defined the screw as one of the simple machines and could calculate its (ideal) mechanical advantage . For example, Heron of Alexandria (52 AD) listed the screw as one of the five mechanisms that could "set

765-417: Is insufficient, an excessive load on a nut with a large thread angle can split the nut. The thread angle also has an effect on the strength of the threads; threads with a large angle have a wide root compared with their size and are stronger. In threaded fasteners , large amounts of friction are acceptable and usually wanted, to prevent the fastener from unscrewing. So threads used in fasteners usually have

810-415: Is lost to friction. When friction is included, the mechanical advantage is no longer equal to the distance ratio but also depends on the screw's efficiency. From conservation of energy , the work W in done on the screw by the input force turning it is equal to the sum of the work done moving the load W out , and the work dissipated as heat by friction W fric in the screw The efficiency η

855-401: Is more applicable. Left-handed screw threads are also used in some other applications: Different shapes (profiles) of threads are used in screws employed for different purposes. Screw threads are standardized so that parts made by different manufacturers will mate correctly. The thread angle is the included angle , measured at a section parallel to the axis, between the two bearing faces of

900-427: Is one of the six classical simple machines . The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside. The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to

945-506: Is raised to. A screw will be self-locking if and only if its efficiency η {\displaystyle \eta \,} is below 50%. Whether a screw is self-locking ultimately depends on the pitch angle and the coefficient of friction of the threads; very well-lubricated, low friction threads with a large enough pitch may "overhaul". Also considerations should be made to ensure that clamped components are clamped tight enough to prevent movement completely. If not, slipping in

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990-432: Is that for a right-handed person, tightening a right-handed screw with a screwdriver is easier than tightening a left-handed screw, because it uses the stronger supinator muscle of the arm rather than the weaker pronator muscle. Since most people are right-handed, right-handed threads became standard on threaded fasteners. Screw linkages in machines are exceptions; they can be right- or left-handed depending on which

1035-503: Is the only source of theoretical observations about contemporary Frisian literature . From 1830 to 1848, for instance, it published 140 literary reviews, most by Frisian authors, and 46 articles on literary topics, sixteen of which on Frisian authors (twelve out of those sixteen on authors who wrote before 1800): the literary reviews and articles provide valuable insight in West Frisian (and Dutch) literature and contemporary attitudes toward

1080-474: The Industrial Revolution brought forth the development of cylinder presses , powered by steam or mechanized systems. These presses could print thousands of pages per hour, marking a substantial leap in production capabilities. In the late 19th century, the introduction of offset lithography revolutionized the printing industry. This technique used a flat metal plate with an image to transfer ink to

1125-664: The Neo-Assyrian period (911-609) BC, and then later appeared in Ancient Egypt and Ancient Greece . Records indicate that the water screw , or screw pump , was first used in Ancient Egypt, some time before the Greek philosopher Archimedes described the Archimedes screw water pump around 234 BC. Archimedes wrote the earliest theoretical study of the screw as a machine, and

1170-439: The fastener by turning it puts compression force on the materials or parts being fastened together, but no amount of force from the parts will cause the screw to turn backwards and untighten. This property is also the basis for the use of screws in screw top container lids , vises , C-clamps , and screw jacks . A heavy object can be raised by turning the jack shaft, but when the shaft is released it will stay at whatever height it

1215-413: The input force required to turn a screw depends on how far from the shaft it is applied; the farther from the shaft, the less force is needed to turn it. The force on a screw is not usually applied at the rim as assumed above. It is often applied by some form of lever; for example a bolt is turned by a wrench whose handle functions as a lever. The mechanical advantage in this case can be calculated by using

1260-438: The larger the mechanical advantage, and the larger the force the screw can exert for a given applied force. However most actual screws have large amounts of friction and their mechanical advantage is less than given by the above equation. The rotational force applied to the screw is actually a torque T i n = F i n r {\displaystyle T_{in}=F_{in}r\,} . Because of this,

1305-424: The length of the lever arm for r in the above equation. This extraneous factor r can be removed from the above equation by writing it in terms of torque: Because of the large area of sliding contact between the moving and stationary threads, screws typically have large frictional energy losses. Even well-lubricated jack screws have efficiencies of only 15% - 20%, the rest of the work applied in turning them

1350-852: The literary past. Only some of the content of "Mengelwerk" was in West Frisian, and today still the paper publishes mostly articles written in Dutch; it was estimated that only around 5% of its content (and that of its main competitor, the Friesch Dagblad ) is in West Frisian. 53°11′48″N 5°48′05″E  /  53.19667°N 5.80139°E  / 53.19667; 5.80139 Printer (publisher) In publishing, printers are both companies providing printing services and individuals who directly operate printing presses . The history of printers in publishing in Western Europe dates back to

1395-552: The mechanical advantage of an actual screw is reduced from what it would be in an ideal, frictionless screw by the efficiency η {\displaystyle \eta \,} . Because of their low efficiency, in powered machinery screws are not often used as linkages to transfer large amounts of power but are more often used in positioners that operate intermittently. Large frictional forces cause most screws in practical use to be " self-locking ", also called " non-reciprocal " or " non-overhauling ". This means that applying

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1440-399: The medium surrounding it; for example rotating a wood screw forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a nut can rotate around a stationary screw shaft. Geometrically, a screw can be viewed as a narrow inclined plane wrapped around a cylinder . Like the other simple machines

1485-444: The mid-15th century with the invention of the printing press. Johannes Gutenberg , a German goldsmith , is credited with developing movable type in the 1450s. His printing press incorporated various innovative techniques, such as individual metal letter blocks and an oil-based ink, enabling faster and more efficient book production. Gutenberg's press set the foundation for subsequent developments in printing technology. It comprised

1530-518: The paper until 1854. His heirs owned the newspaper until 1947. In 2013 Leeuwarder Courant was awarded the European Newspaper of the Year in the category of regional newspapers. While initially publishing mainly business and international news, in the nineteenth century the paper improved in quality and layout, and began publishing more news and stories related to Friesland. Important in this respect

1575-503: The region, which helped ensure its commercial success, and until 1842 it was the only serious newspaper in Friesland. After Ferwerda's death, his son-in-law, Doeke Ritske Smeding, took over and guided the paper though the French occupation of the early nineteenth century (during which many Dutch papers were shut down by the occupier). Smeding died in 1814; Pieter Koumans Smeding, his nephew, ran

1620-471: The reviews, in most cases without a byline, and in one case Eekhoff recommended a poetry collection he had written himself. The literary criticism in the Leeuwarder Courant is especially significant since its readership was to be found in the upper circles of Frisian society—the bookbuying public, the notables who were greatly interested in matters of language, literature, and culture, and helped determine their society's tastes and predilections. Additionally, it

1665-403: The rotational force F in applied to the rim of the shaft to turn it. For a screw with no friction (also called an ideal screw ), from conservation of energy the work done on the screw by the input force turning it is equal to the work done by the screw on the load force: Work is equal to the force multiplied by the distance it acts, so the work done in one complete turn of the screw

1710-508: The same principle, also called screws, do not necessarily have a shaft or threads. For example, a corkscrew is a helix-shaped rod with a sharp point, and an Archimedes' screw is a water pump that uses a rotating helical chamber to move water uphill. The common principle of all screws is that a rotating helix can cause linear motion. The screw was one of the last of the simple machines to be invented. It first appeared in Mesopotamia during

1755-466: The screw in this "backwards" sense, applying axial force to the shaft to turn the screw. Other reasons for the screws to come loose are incorrect design of assembly and external forces such as shock, vibration and dynamic loads causing slipping on the threaded and mated/clamped surfaces. This self-locking property is one reason for the very large use of the screw in threaded fasteners such as wood screws , sheet metal screws , studs and bolts. Tightening

1800-399: The shaft in the direction of rotation, the thumb will point in the direction of motion of the shaft. 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. One explanation for why right-handed threads became standard

1845-403: The thread. The angle between the axial load force and the normal to the bearing surface is approximately equal to half the thread angle, so the thread angle has a great effect on the friction and efficiency of a screw, as well as the wear rate and the strength. The greater the thread angle, the greater the angle between the load vector and the surface normal, so the larger the normal force between

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1890-402: The threads required to support a given load. Therefore, increasing the thread angle increases the friction and wear of a screw. The outward facing angled thread bearing surface, when acted on by the load force, also applies a radial (outward) force to the nut, causing tensile stress . This radial bursting force increases with increasing thread angle. If the tensile strength of the nut material

1935-605: Was also apparently applied to drilling and moving materials (besides water) around this time, when images of augers and drills began to appear in European paintings. The complete dynamic theory of simple machines, including the screw, was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche ("On Mechanics"). The fineness or coarseness of a screw's threads are defined by two closely related quantities: In most screws, called " single start " screws, which have

1980-459: Was also to focus on mercantile and international news, rather than report on too many local issues which might cause controversy with the local and national governments. In fact, during the latter part of the eighteenth century (the period which saw the decline of the Dutch Republic ) the paper was criticized for its lack of patriotism. For a long time it was the only medium for advertisements in

2025-512: Was the column "Mengelwerk," a kind of Frisian miscellany, which was published every Tuesday starting February 2, 1830, and included anecdotes and stories, and usually Frisian matters. Most of these anecdotes were written in Dutch , though the occasional West Frisian entry was printed. In the early to mid nineteenth century, the Leeuwarder Courant began to publish literary reviews. Jacob van Leeuwen (1787–1857) and Wopke Eekhoff (1809–1880) wrote most of

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