A screw is an externally helical threaded fastener capable of being tightened or released by a twisting force ( torque ) to the head . The most common uses of screws are to hold objects together and there are many forms for a variety of materials. Screws might be inserted into holes in assembled parts or a screw may form its own thread. The difference between a screw and a bolt is that the latter is designed to be tightened or released by torquing a nut .
164-443: At a minimum, a screw drive is a set of shaped cavities and protrusions on the screw head that allows torque to be applied to it. Usually, it also involves a mating tool , such as a screwdriver , that is used to turn it. Some of the less-common drives are classified as being "tamper-resistant". Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00". [REDACTED] Slot screw drives have
328-417: A female threaded fastener other than a nut. Sheet-metal screws do not have the chip-clearing flute of self-tapping screws. However, some wholesale vendors do not distinguish between the two kinds. A wood screw is a metal screw used to fix wood, with a sharp point and a tapered thread designed to cut its own thread into the wood. Some screws are driven into intact wood; larger screws are usually driven into
492-417: A female threaded fastener other than a nut. Sheet-metal screws do not have the chip-clearing flute of self-tapping screws. However, some wholesale vendors do not distinguish between the two kinds. A wood screw is a metal screw used to fix wood, with a sharp point and a tapered thread designed to cut its own thread into the wood. Some screws are driven into intact wood; larger screws are usually driven into
656-449: A screw machine of an early and prescient sort. It made use of a leadscrew to guide the cutter to produce the desired pitch, and the slot was cut with a rotary file while the main spindle held still (presaging live tools on lathes 250 years later). Not until 1776 did the Wyatt brothers have a wood-screw factory up and running. Their enterprise failed, but new owners soon made it prosper, and in
820-401: A screw machine of an early and prescient sort. It made use of a leadscrew to guide the cutter to produce the desired pitch, and the slot was cut with a rotary file while the main spindle held still (presaging live tools on lathes 250 years later). Not until 1776 did the Wyatt brothers have a wood-screw factory up and running. Their enterprise failed, but new owners soon made it prosper, and in
984-455: A "PH" or "PZ" followed by the size number (000, 00, 0, 1, 2, 3), though not all manufacturers do this. Unlike JIS, the ISO 4757 standard for cross-head screws does not specify a dot on the screw head. [REDACTED] Phillips II recesses are compatible with Phillips drivers, but have a vertical rib in between the cruciform recesses that interacts with horizontal ribs on a Phillips II driver to create
1148-670: A Phillips or Pozidriv head screw slightly loosely, but without damage. JIS heads are often identified by a single dot or an "X" to one side of the cross slot, though this is not always the case. "JIS" or ISO 8764 standardized cruciform-blade screwdrivers are available for this type of screw, and should always be used to avoid head and driver damage. [REDACTED] (PH) [REDACTED] (PZ) ISO 8764 PH drivers are nearly identical to JIS B 1012 drivers. ISO 8764 has superseded JIS B 1012 in Japan as well as being used in many other countries. The standard specifies that drivers and bits are to be marked with
1312-453: A Phillips screw albeit one with narrower and more vertical slots. Compared to Phillips screws these differences give JIS fasteners less of a tendency to cam out . The bottom of the recess is flat, and the point of the driver has to be blunt. A Phillips screwdriver has the same 26.5 degree cone angle but because of the tapered slots will not seat fully, and will damage the screw if forced. A correctly sized JIS driver will engage at full depth into
1476-586: A classic North American 1 ⁄ 4 -inch screwdriver although the North American one is often a bit thinner (≈1.0 mm). At least one mechanical method of temporarily holding a slotted screw to a matching screwdriver is available, the Quick-Wedge screw-holding screwdriver, first manufactured by the Kedman Company in the 1950s. Dzus fasteners , which have a cam-lock body instead of a threaded body, use
1640-402: A hole narrower than the screw thread, and cut the thread in the wood. Early wood screws were made by hand, with a series of files, chisels, and other cutting tools, and these can be spotted easily by noting the irregular spacing and shape of the threads, as well as file marks remaining on the head of the screw and in the area between threads. Many of these screws had a blunt end, completely lacking
1804-402: A hole narrower than the screw thread, and cut the thread in the wood. Early wood screws were made by hand, with a series of files, chisels, and other cutting tools, and these can be spotted easily by noting the irregular spacing and shape of the threads, as well as file marks remaining on the head of the screw and in the area between threads. Many of these screws had a blunt end, completely lacking
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#17328694095141968-501: A leader in machine tools for decades afterward. A misquoting of James Nasmyth popularized the notion that Maudslay had invented the slide rest, but this was incorrect; however, his lathes helped to popularize it. These developments of the 1760–1800 era, with the Wyatts and Maudslay as arguably the most important drivers, caused great increase in the use of threaded fasteners. Standardization of threadforms began almost immediately, but it
2132-452: A leader in machine tools for decades afterward. A misquoting of James Nasmyth popularized the notion that Maudslay had invented the slide rest, but this was incorrect; however, his lathes helped to popularize it. These developments of the 1760–1800 era, with the Wyatts and Maudslay as arguably the most important drivers, caused great increase in the use of threaded fasteners. Standardization of threadforms began almost immediately, but it
2296-471: A nearby forge. The screw mill was not a commercial success; it eventually failed due to competition from the lower-cost, gimlet-pointed screw, and ceased operations in 1836. The American development of the turret lathe (1840s) and of automatic screw machines derived from it (1870s) drastically reduced the unit cost of threaded fasteners by increasingly automating the machine-tool control. This cost reduction spurred ever greater use of screws. Throughout
2460-471: A nearby forge. The screw mill was not a commercial success; it eventually failed due to competition from the lower-cost, gimlet-pointed screw, and ceased operations in 1836. The American development of the turret lathe (1840s) and of automatic screw machines derived from it (1870s) drastically reduced the unit cost of threaded fasteners by increasingly automating the machine-tool control. This cost reduction spurred ever greater use of screws. Throughout
2624-409: A pilot hole in a substrate, and most are classed as screws. Mating threads are formed in the substrate as these fasteners are driven in. Fasteners with a non-tapered shank are generally designed to mate with a nut or to be driven into a tapped hole, and most would be classed as bolts , although some are thread-forming (eg. taptite ) and some authorities would treat some as screws when they are used with
2788-409: A pilot hole in a substrate, and most are classed as screws. Mating threads are formed in the substrate as these fasteners are driven in. Fasteners with a non-tapered shank are generally designed to mate with a nut or to be driven into a tapped hole, and most would be classed as bolts , although some are thread-forming (eg. taptite ) and some authorities would treat some as screws when they are used with
2952-535: A pointed tip, and rounded corners, a Pozidriv screwdriver has parallel flanks, a blunt tip, and additional smaller ribs at 45° to the main slots. Both Phillips and Pozidriv bit types can be manufactured in four cuts from a tapered blank, although Pozidriv screwdriver bits require a slightly more complex cutter than for Phillips bits. Pozidriv and Phillips look broadly interchangeable, but may cause damage if mixed. Pozidriv screwdrivers will jam fit into Phillips screws, but when tightened they may slip or tear out
3116-517: A popular belief that this was a deliberate feature of the design, to assemble aluminium aircraft without overtightening the fasteners. There is no good evidence for this suggestion, and the property is not mentioned in the original patents. [REDACTED] The Pozidriv, sometimes incorrectly spelled "Pozidrive", is an improved version of the Phillips screw drive. It is designated "Type IA" by ANSI standards. and "Type Z" in ISO documents. The Pozidriv
3280-405: A simple handtool. The slotted screw is commonly found in existing products and installations, along with use in simple carpentry work and in applications where minimal torque is needed. Slot screws are also used in the restoration of antique furniture, vehicles, and equipment. However, this design is not well-suited for installation by power tools , given that a power driver often cams out of
3444-463: A simple slot's "minus" (−). A double slotted screw drive is not considered cruciform because the shape is not recessed, and consists only of two orthogonal simple milled slots. Some of these types are specified in ISO 4757, Cross recesses for screws . Cruciform Phillips and Pozidriv/Supadriv screws and screwdrivers look similar, and are often confused with each other; a Phillips screwdriver will often work with Pozidriv/Supadriv screws, but risks damaging
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#17328694095143608-406: A single horizontal indentation (the slot ) in the fastener head and is driven by a "common blade" or flat-bladed screwdriver . This form was the first type of screw drive to be developed, and, for centuries, it was the simplest and cheapest to make because it can just be sawed or filed. Additionally, it is unique because the slot head is straightforward to manufacture, and because it can be driven by
3772-510: A slot drive. [REDACTED] Coin-slot drives are so-called because of the curved bottom of the recess, which facilitates driving them with a suitable coin . They are often used on items where the user is not likely to have a screwdriver when needed, such as recessed screws that attach cameras to tripod adapters , and battery compartments in some equipment such as children's toys. [REDACTED] Hi-Torque slot drives were designed by Alcoa Fastening Systems, for situations where very high torque
3936-536: A square), rather than the 120° internal angle of a hexagon. In practice, drivers for the fasteners may be interchangeable but should be examined carefully for proper fit before application of force. A hex key should not be used where a key of square cross-section is the correct fit. Triple-square fasteners are referred to as "spline" in the UK. This is potentially confusing if looking for the more unusual 12-spline flange type. While they are distinguished under close inspection by
4100-618: A standard (in about 1841) was the English engineer Sir Joseph Whitworth . Whitworth screw sizes are still used, both for repairing old machinery and where a coarser thread than the metric fastener thread is required. Whitworth became British Standard Whitworth , abbreviated to BSW (BS 84:1956) and the British Standard Fine (BSF) thread was introduced in 1908 because the Whitworth thread was too coarse for some applications. The thread angle
4264-454: A standard (in about 1841) was the English engineer Sir Joseph Whitworth . Whitworth screw sizes are still used, both for repairing old machinery and where a coarser thread than the metric fastener thread is required. Whitworth became British Standard Whitworth , abbreviated to BSW (BS 84:1956) and the British Standard Fine (BSF) thread was introduced in 1908 because the Whitworth thread was too coarse for some applications. The thread angle
4428-527: A stick-fit, and to provide anti cam-out properties (the ribs are trademarked as "ACR" for Anti Cam-out Ribs). [REDACTED] The Frearson screw drive, also known as the Reed and Prince screw drive, and specified as ANSI Type II Cross Recess, is similar to a Phillips but the Frearson has a sharp tip and larger angle in the V shape. One advantage over the Phillips drive is that one driver or bit fits all screw sizes. It
4592-459: A successive 30° rotation. The design is similar to that of the double-square , in both cases the idea being that it resembles a square (Robertson) but can be engaged at more frequent angles by the driver bit. These screws can be driven with standard Robertson bits. Sizes are: M4 , M5 , M6 , (M7), M8 , (M9), M10 , (M11), M12 , (M13), M14 , (M15), M16 , (M17) and M18 (the sizes in parentheses are less commonly used, but they do exist). Despite
4756-406: A two-step driver design, with the blade diameter increasing a certain distance from the point. [REDACTED] Torq-set is a cruciform screw drive used in torque-sensitive applications. The Torq-set head is similar in appearance to a Phillips drive in that it has a cross with 4 arms. In Torq-set however, the lines are offset from each other, so they do not align to form intersecting slots across
4920-452: A variety of materials. Screws might be inserted into holes in assembled parts or a screw may form its own thread. The difference between a screw and a bolt is that the latter is designed to be tightened or released by torquing a nut . The screw head on one end has a milled slot that commonly requires a tool to transfer the twisting force. Common tools for driving screws include screwdrivers , wrenches , coins and hex keys . The head
5084-456: A variety of screw head shapes. A few varieties of screw are manufactured with a break-away head, which snaps off when adequate torque is applied, to prevent removal after fitting, often to avoid tampering. The international standards for metric externally threaded fasteners are ISO 898-1 for property classes produced from carbon steels and ISO 3506-1 for property classes produced from corrosion resistant steels. There are many standards governing
List of screw drives - Misplaced Pages Continue
5248-456: A variety of screw head shapes. A few varieties of screw are manufactured with a break-away head, which snaps off when adequate torque is applied, to prevent removal after fitting, often to avoid tampering. The international standards for metric externally threaded fasteners are ISO 898-1 for property classes produced from carbon steels and ISO 3506-1 for property classes produced from corrosion resistant steels. There are many standards governing
5412-441: A very high production rate, and produces virtually no waste material. Slotted head screws require an extra step to cut the slot in the head; this is done on a slotting machine . These machines are essentially stripped down milling machines designed to process as many blanks as possible. The blanks are then polished again prior to threading. The threads are usually produced via thread rolling ; however, some are cut . The workpiece
5576-441: A very high production rate, and produces virtually no waste material. Slotted head screws require an extra step to cut the slot in the head; this is done on a slotting machine . These machines are essentially stripped down milling machines designed to process as many blanks as possible. The blanks are then polished again prior to threading. The threads are usually produced via thread rolling ; however, some are cut . The workpiece
5740-452: Is 0.25–3 in (6.35–76.20 mm) in diameter . In 1991, responding to an influx of counterfeit fasteners, Congress passed PL 101-592, the "Fastener Quality Act". As a result, the ASME B18 committee re-wrote B18.2.1, renaming finished hex bolts to hex cap screw – a term that had existed in common usage long before, but was now also being codified as an official name for
5904-401: Is 0.25–3 in (6.35–76.20 mm) in diameter . In 1991, responding to an influx of counterfeit fasteners, Congress passed PL 101-592, the "Fastener Quality Act". As a result, the ASME B18 committee re-wrote B18.2.1, renaming finished hex bolts to hex cap screw – a term that had existed in common usage long before, but was now also being codified as an official name for
6068-491: Is 1/4" Whitworth (20 tpi) and for medium/large format cameras is 3/8" Whitworth (16 tpi). It is also used for microphone stands and their appropriate clips, again in both sizes, along with "thread adapters" to allow the smaller size to attach to items requiring the larger thread. Note that while 1/4" UNC bolts fit 1/4" BSW camera tripod bushes, yield strength is reduced by the different thread angles of 60° and 55° respectively. British Association (BA) screw threads, named after
6232-491: Is 1/4" Whitworth (20 tpi) and for medium/large format cameras is 3/8" Whitworth (16 tpi). It is also used for microphone stands and their appropriate clips, again in both sizes, along with "thread adapters" to allow the smaller size to attach to items requiring the larger thread. Note that while 1/4" UNC bolts fit 1/4" BSW camera tripod bushes, yield strength is reduced by the different thread angles of 60° and 55° respectively. British Association (BA) screw threads, named after
6396-474: Is 400 MPa ultimate strength and 0.6*400=240 MPa yield strength. High-strength steel bolts have property class 8.8, which is 800 MPa ultimate strength and 0.8*800=640 MPa yield strength or above. Screw#Pan head A screw is an externally helical threaded fastener capable of being tightened or released by a twisting force ( torque ) to the head . The most common uses of screws are to hold objects together and there are many forms for
6560-408: Is a misnomer ) or French wood screw (Scandinavia) are large wood screws. Lag screws are used to lag together lumber framing, to lag machinery feet to wood floors, and for other heavy carpentry applications. The attributive modifier lag came from an early principal use of such fasteners: the fastening of lags such as barrel staves and other similar parts. These fasteners are "screws" according to
6724-408: Is a misnomer ) or French wood screw (Scandinavia) are large wood screws. Lag screws are used to lag together lumber framing, to lag machinery feet to wood floors, and for other heavy carpentry applications. The attributive modifier lag came from an early principal use of such fasteners: the fastening of lags such as barrel staves and other similar parts. These fasteners are "screws" according to
List of screw drives - Misplaced Pages Continue
6888-706: Is a spanner (UK usage) or wrench (US usage), while a nut setter is used with a power screw driver. Modern screws employ a wide variety of screw drive designs , each requiring a different kind of tool to drive in or extract them. The most common screw drives are the slotted and Phillips in the US; hex, Robertson, and Torx are also common in some applications, and Pozidriv has almost completely replaced Phillips in Europe. Some types of drive are intended for automatic assembly in mass-production of such items as automobiles. More exotic screw drive types may be used in situations where tampering
7052-612: Is a spanner (UK usage) or wrench (US usage), while a nut setter is used with a power screw driver. Modern screws employ a wide variety of screw drive designs , each requiring a different kind of tool to drive in or extract them. The most common screw drives are the slotted and Phillips in the US; hex, Robertson, and Torx are also common in some applications, and Pozidriv has almost completely replaced Phillips in Europe. Some types of drive are intended for automatic assembly in mass-production of such items as automobiles. More exotic screw drive types may be used in situations where tampering
7216-399: Is called a screwdriver . A power tool that does the same job is a power screwdriver ; power drills may also be used with screw-driving attachments. Where the holding power of the screwed joint is critical, torque-measuring and torque-limiting screwdrivers are used to ensure sufficient but not excessive force is developed by the screw. The hand tool for driving hex head threaded fasteners
7380-399: Is called a screwdriver . A power tool that does the same job is a power screwdriver ; power drills may also be used with screw-driving attachments. Where the holding power of the screwed joint is critical, torque-measuring and torque-limiting screwdrivers are used to ensure sufficient but not excessive force is developed by the screw. The hand tool for driving hex head threaded fasteners
7544-567: Is called a right-hand thread . Screws with a left-hand thread are used in exceptional cases, such as where the screw will be subject to counterclockwise torque , which would tend to loosen a right-hand screw. For this reason, the left-side pedal of a bicycle has a left-hand thread . The screw mechanism is one of the six classical simple machines defined by Renaissance scientists. Fasteners had become widespread involving concepts such as dowels and pins, wedging, mortises and tenons , dovetails , nailing (with or without clenching
7708-567: Is called a right-hand thread . Screws with a left-hand thread are used in exceptional cases, such as where the screw will be subject to counterclockwise torque , which would tend to loosen a right-hand screw. For this reason, the left-side pedal of a bicycle has a left-hand thread . The screw mechanism is one of the six classical simple machines defined by Renaissance scientists. Fasteners had become widespread involving concepts such as dowels and pins, wedging, mortises and tenons , dovetails , nailing (with or without clenching
7872-518: Is credited with forming a company ( Phillips Screw Company ), improving the design, and promoting the adoption of his product. The original 1932 patent expired in 1966, but the Phillips Screw Company continued to develop improved designs. The American Screw Company of Providence, Rhode Island , was responsible for devising a means of efficiently manufacturing the screw, and successfully patented and licensed their method; other screw makers of
8036-537: Is needed, along with the ability to repeatedly install and remove the fastener. The design features curved walls, unlike the straight-walled slot drive. The Type II (Conical/Connie) design adds a conical cup that receives a centering pin on the driver, improving the alignment of the driving tool to the fastener recess. The following are screw drives based on a cruciform (cross) shape. Other names used for these types of drives are cross recessed , cross-head , cross tip , and cross-point ; sometimes "plus" (+) as against
8200-432: Is normally used in screws with nominal diameters of 2–3 mm , PZ2 in 3.5–5 mm screws and PZ3 in 5.5–8 mm . These sizes roughly correspond to the Phillips head numbers. Pozidriv screws have a set of radial indentations (tick marks) set at 45° from the main cross recess on the head of the screw, which makes them visually distinct from Phillips screws. While a Phillips screwdriver has slightly tapered flanks,
8364-442: Is often found in marine hardware and requires a Frearson screwdriver or bit to work properly. The tool recess is a perfect, sharp cross, allowing for higher applied torque, unlike the rounded, tapered Phillips head, which can cam out at high torque. It was developed by an English inventor named Frearson in the 19th century and produced from the late 1930s to the mid-1970s. The Reed & Prince Mfg. Company of Worcester, Massachusetts,
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#17328694095148528-453: Is similar to a square drive (Robertson) but can be engaged at more frequent angles by the driver bit. [REDACTED] The triple-square , also known as XZN , is a type of screw drive with 12 equally spaced protrusions, each ending in a 90° internal angle. The name derives from overlaying three equal squares to form such a pattern with 12 right-angled protrusions (a 12-pointed star). In other words, three Robertson squares are superimposed at
8692-609: Is the outer diameter of the thread. The tapped hole (or nut) into which the screw fits, has an internal diameter which is the size of the screw minus the pitch of the thread. Thus, an M6 screw, which has a pitch of 1 mm, is made by threading a 6 mm shank, and the nut or threaded hole is made by tapping threads into a hole of 5 mm diameter (6 mm − 1 mm). Metric hexagon bolts, screws and nuts are specified, for example, in International Standards ISO 4014, ISO 4017, and ISO 4032. The following table lists
8856-540: Is the outer diameter of the thread. The tapped hole (or nut) into which the screw fits, has an internal diameter which is the size of the screw minus the pitch of the thread. Thus, an M6 screw, which has a pitch of 1 mm, is made by threading a 6 mm shank, and the nut or threaded hole is made by tapping threads into a hole of 5 mm diameter (6 mm − 1 mm). Metric hexagon bolts, screws and nuts are specified, for example, in International Standards ISO 4014, ISO 4017, and ISO 4032. The following table lists
9020-423: Is the tensile stress at which the bolt fails. Tensile yield strength is the stress at which the bolt will yield in tension across the entire section of the bolt and receive a permanent set (an elongation from which it will not recover when the force is removed) of 0.2% offset strain . Proof strength is the usable strength of the fastener. Tension testing of a bolt up to the proof load should not cause permanent set of
9184-423: Is the tensile stress at which the bolt fails. Tensile yield strength is the stress at which the bolt will yield in tension across the entire section of the bolt and receive a permanent set (an elongation from which it will not recover when the force is removed) of 0.2% offset strain . Proof strength is the usable strength of the fastener. Tension testing of a bolt up to the proof load should not cause permanent set of
9348-400: Is then cold headed , which is a cold working process. Heading produces the head of the screw. The shape of the die in the machine dictates what features are pressed into the screw head; for example a flat head screw uses a flat die. For more complicated shapes two heading processes are required to get all of the features into the screw head. This production method is used because heading has
9512-400: Is then cold headed , which is a cold working process. Heading produces the head of the screw. The shape of the die in the machine dictates what features are pressed into the screw head; for example a flat head screw uses a flat die. For more complicated shapes two heading processes are required to get all of the features into the screw head. This production method is used because heading has
9676-399: Is then tumble finished with wood and leather media to do final cleaning and polishing. For most screws, a coating, such as electroplating with zinc ( galvanizing ) or applying black oxide , is applied to prevent corrosion. Threaded fasteners either have a tapered shank or a non-tapered shank. Fasteners with tapered shanks are designed to either be driven into a substrate directly or into
9840-399: Is then tumble finished with wood and leather media to do final cleaning and polishing. For most screws, a coating, such as electroplating with zinc ( galvanizing ) or applying black oxide , is applied to prevent corrosion. Threaded fasteners either have a tapered shank or a non-tapered shank. Fasteners with tapered shanks are designed to either be driven into a substrate directly or into
10004-627: Is undesirable, such as in electronic appliances that should not be serviced by the home repair person. There are many systems for specifying the dimensions of screws, but in much of the world the ISO metric screw thread preferred series has displaced the many older systems. Other relatively common systems include the British Standard Whitworth , BA system (British Association) , and the Unified Thread Standard . The basic principles of
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#173286940951410168-449: Is undesirable, such as in electronic appliances that should not be serviced by the home repair person. There are many systems for specifying the dimensions of screws, but in much of the world the ISO metric screw thread preferred series has displaced the many older systems. Other relatively common systems include the British Standard Whitworth , BA system (British Association) , and the Unified Thread Standard . The basic principles of
10332-417: Is used for the design of the punches, bits, and screws. Files are sent over to manufacturers containing these models so that there is no miscommunication and all the parts are the same across the board. [REDACTED] A Robertson screw , also known as a square or Scrulox screw drive, is specified as ANSI Type III Square Center and has a square -shaped socket in the screw head and a square protrusion on
10496-507: Is usually a smaller fastener (less than 1 ⁄ 4 inch (6.35 mm) in diameter) threaded the entire length of its shank that usually has a recessed drive type (slotted, Phillips, etc.), usually intended to screw into a pre-formed thread, either a nut or a threaded (tapped) hole, unlike a wood or self-tapping screw. Machine screws are also made with socket heads (see above), often referred to as socket-head machine screws. ASME standard B18.2.1-1996 specifies hex cap screws whose size range
10660-507: Is usually a smaller fastener (less than 1 ⁄ 4 inch (6.35 mm) in diameter) threaded the entire length of its shank that usually has a recessed drive type (slotted, Phillips, etc.), usually intended to screw into a pre-formed thread, either a nut or a threaded (tapped) hole, unlike a wood or self-tapping screw. Machine screws are also made with socket heads (see above), often referred to as socket-head machine screws. ASME standard B18.2.1-1996 specifies hex cap screws whose size range
10824-448: Is usually larger than the body, which provides a bearing surface and keeps the screw from being driven deeper than its length; an exception being the set screw (aka grub screw ). The cylindrical portion of the screw from the underside of the head to the tip is called the shank ; it may be fully or partially threaded with the distance between each thread called the pitch . Most screws are tightened by clockwise rotation, which
10988-448: Is usually larger than the body, which provides a bearing surface and keeps the screw from being driven deeper than its length; an exception being the set screw (aka grub screw ). The cylindrical portion of the screw from the underside of the head to the tip is called the shank ; it may be fully or partially threaded with the distance between each thread called the pitch . Most screws are tightened by clockwise rotation, which
11152-816: The Machinery's Handbook criteria, and the obsolescent term "lag bolt" has been replaced by "lag screw" in the Handbook . However, based on tradition many tradesmen continue to refer to them as "bolts", because, like head bolts, they are large, with hex or square heads that require a wrench, socket, or specialized bit to turn. The head is typically an external hex. Metric hex-headed lag screws are covered by DIN 571. Inch square-headed and hex-headed lag screws are covered by ASME B18.2.1. A typical lag screw can range in diameter from 4 to 20 mm or #10 to 1.25 in (4.83 to 31.75 mm), and lengths from 16 to 200 mm or 1 ⁄ 4 to 6 in (6.35 to 152.40 mm) or longer, with
11316-715: The Machinery's Handbook criteria, and the obsolescent term "lag bolt" has been replaced by "lag screw" in the Handbook . However, based on tradition many tradesmen continue to refer to them as "bolts", because, like head bolts, they are large, with hex or square heads that require a wrench, socket, or specialized bit to turn. The head is typically an external hex. Metric hex-headed lag screws are covered by DIN 571. Inch square-headed and hex-headed lag screws are covered by ASME B18.2.1. A typical lag screw can range in diameter from 4 to 20 mm or #10 to 1.25 in (4.83 to 31.75 mm), and lengths from 16 to 200 mm or 1 ⁄ 4 to 6 in (6.35 to 152.40 mm) or longer, with
11480-504: The United States , but is also extensively used in Canada and occasionally in other countries. The size of a UTS screw is described using the following format: X-Y , where X is the nominal size (the hole or slot size in standard manufacturing practice through which the shank of the screw can easily be pushed) and Y is the threads per inch (TPI). For sizes 1 ⁄ 4 inch and larger
11644-401: The United States , but is also extensively used in Canada and occasionally in other countries. The size of a UTS screw is described using the following format: X-Y , where X is the nominal size (the hole or slot size in standard manufacturing practice through which the shank of the screw can easily be pushed) and Y is the threads per inch (TPI). For sizes 1 ⁄ 4 inch and larger
11808-412: The industrial revolution . They are key components of micrometers and lathes. There are three steps in manufacturing a screw: heading , thread rolling , and coating . Screws are normally made from wire , which is supplied in large coils, or round bar stock for larger screws. The wire or rod is then cut to the proper length for the type of screw being made; this workpiece is known as a blank . It
11972-412: The industrial revolution . They are key components of micrometers and lathes. There are three steps in manufacturing a screw: heading , thread rolling , and coating . Screws are normally made from wire , which is supplied in large coils, or round bar stock for larger screws. The wire or rod is then cut to the proper length for the type of screw being made; this workpiece is known as a blank . It
12136-427: The 15th century, if known at all. The metal screw did not become a common fastener until machine tools for mass production developed toward the end of the 18th century. This development blossomed in the 1760s and 1770s. along two separate paths that soon converged : The first path was pioneered by brothers Job and William Wyatt of Staffordshire , UK, who patented in 1760 a machine that one might today best call
12300-427: The 15th century, if known at all. The metal screw did not become a common fastener until machine tools for mass production developed toward the end of the 18th century. This development blossomed in the 1760s and 1770s. along two separate paths that soon converged : The first path was pioneered by brothers Job and William Wyatt of Staffordshire , UK, who patented in 1760 a machine that one might today best call
12464-406: The 1780s they were producing 16,000 screws a day with only 30 employees —the kind of industrial productivity and output volume that would later become characteristic of modern industry but which was revolutionary at the time. Meanwhile, English instrument-maker Jesse Ramsden (1735–1800) was working on the toolmaking and instrument-making end of the screw-cutting problem, and in 1777 he invented
12628-406: The 1780s they were producing 16,000 screws a day with only 30 employees —the kind of industrial productivity and output volume that would later become characteristic of modern industry but which was revolutionary at the time. Meanwhile, English instrument-maker Jesse Ramsden (1735–1800) was working on the toolmaking and instrument-making end of the screw-cutting problem, and in 1777 he invented
12792-511: The 1930s dismissed the Phillips concept because it called for a relatively complex recessed socket shape in the head of the screw, as distinct from the simple milled slot of a slotted screw. The Phillips screw design was developed as a direct solution to several problems with slotted screws: high cam-out potential; need for precise alignment to avoid slippage and damage to driver, fastener, and adjacent surfaces; and difficulty of driving with powered tools. Phillips drive bits are often designated by
12956-410: The 19th century, the most commonly used forms of screw head (that is, drive types ) were simple internal-wrenching straight slots and external-wrenching squares and hexagons. These were easy to machine and served most applications adequately. Rybczynski describes a flurry of patents for alternative drive types in the 1860s through 1890s, but explains that these were patented but not manufactured due to
13120-410: The 19th century, the most commonly used forms of screw head (that is, drive types ) were simple internal-wrenching straight slots and external-wrenching squares and hexagons. These were easy to machine and served most applications adequately. Rybczynski describes a flurry of patents for alternative drive types in the 1860s through 1890s, but explains that these were patented but not manufactured due to
13284-577: The 1st century BC, wooden screws were commonly used throughout the Mediterranean world in screw presses for pressing olive oil from olives and for pressing juice from grapes in winemaking . The first documentation of the screwdriver is in the medieval Housebook of Wolfegg Castle , a manuscript written sometime between 1475 and 1490. However they probably did not become widespread until after 1800, once threaded fasteners had become commodified. Metal screws used as fasteners were rare in Europe before
13448-522: The 1st century BC, wooden screws were commonly used throughout the Mediterranean world in screw presses for pressing olive oil from olives and for pressing juice from grapes in winemaking . The first documentation of the screwdriver is in the medieval Housebook of Wolfegg Castle , a manuscript written sometime between 1475 and 1490. However they probably did not become widespread until after 1800, once threaded fasteners had become commodified. Metal screws used as fasteners were rare in Europe before
13612-462: The ASME B18 standard. Lug bolt and head bolts are other terms that refer to fasteners that are designed to be threaded into a tapped hole that is in part of the assembly and so based on the Machinery's Handbook distinction they would be screws. Here common terms are at variance with Machinery's Handbook distinction. Lag screws (US) or coach screws (UK, Australia, and New Zealand) (also referred to as lag bolts or coach bolts , although this
13776-462: The ASME B18 standard. Lug bolt and head bolts are other terms that refer to fasteners that are designed to be threaded into a tapped hole that is in part of the assembly and so based on the Machinery's Handbook distinction they would be screws. Here common terms are at variance with Machinery's Handbook distinction. Lag screws (US) or coach screws (UK, Australia, and New Zealand) (also referred to as lag bolts or coach bolts , although this
13940-628: The British Association for Advancement of Science, were devised in 1884 and standardised in 1903. Screws were described as "2BA", "4BA" etc., the odd numbers being rarely used, except in equipment made prior to the 1970s for telephone exchanges in the UK. This equipment made extensive use of odd-numbered BA screws, in order—it may be suspected—to reduce theft. BA threads are specified by British Standard BS 93:1951 "Specification for British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A." While not related to ISO metric screws,
14104-566: The British Association for Advancement of Science, were devised in 1884 and standardised in 1903. Screws were described as "2BA", "4BA" etc., the odd numbers being rarely used, except in equipment made prior to the 1970s for telephone exchanges in the UK. This equipment made extensive use of odd-numbered BA screws, in order—it may be suspected—to reduce theft. BA threads are specified by British Standard BS 93:1951 "Specification for British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A." While not related to ISO metric screws,
14268-533: The ISO metric screw thread are defined in international standard ISO 68-1 and preferred combinations of diameter and pitch are listed in ISO 261. The smaller subset of diameter and pitch combinations commonly used in screws, nuts and bolts is given in ISO 262 . The most commonly used pitch value for each diameter is the coarse pitch . For some diameters, one or two additional fine pitch variants are also specified, for special applications such as threads in thin-walled pipes. ISO metric screw threads are designated by
14432-533: The ISO metric screw thread are defined in international standard ISO 68-1 and preferred combinations of diameter and pitch are listed in ISO 261. The smaller subset of diameter and pitch combinations commonly used in screws, nuts and bolts is given in ISO 262 . The most commonly used pitch value for each diameter is the coarse pitch . For some diameters, one or two additional fine pitch variants are also specified, for special applications such as threads in thin-walled pipes. ISO metric screw threads are designated by
14596-416: The Phillips screw head. Conversely, while Phillips screwdrivers will loosely fit and turn Pozidriv screws, they will cam out if enough torque is applied, potentially damaging the screw head or driver. [REDACTED] The Supadriv (sometimes spelled incorrectly as "Supadrive") screw drive is very similar in function and appearance to Pozidriv. It is a later development by the same company. The description of
14760-477: The Pozidriv head applies also to Supadriv. While each has its own driver, the same screwdriver heads may be used for both types without damage; for most purposes it is unnecessary to distinguish between the two drives. Pozidriv and Supadriv screws are slightly different in detail; the later Supadriv allows a small angular offset between the screw and the screwdriver, while Pozidriv has to be directly in line. In detail,
14924-598: The Supadriv screwhead is similar to Pozidriv but has only two identification ticks, and the secondary blades are larger. Drive blades are about equally thick. The main practical difference is that Supadriv has superior bite when driving screws into vertical or near-vertical surfaces, making screwdriving more efficient, with less cam-out . [REDACTED] The JIS B 1012 was commonly found in Japanese made equipment, such as cameras and motorbikes. JIS fasteners superficially resemble
15088-508: The Torq-set geometry are National Aerospace Standard NASM 33781 and NASM 14191 for the ribbed version. The ribbed version is also known as ACR Torq-set. [REDACTED] The Mortorq drive, developed by the Phillips Screw Company, is a format used in automotive and aerospace applications. It is designed to be a lightweight, low-profile and high-strength drive, with full contact over the entire recess wing, reducing risk of stripping. This low recess
15252-531: The United States are still inch based. The numbers stamped on the head of the bolt are referred to the grade of the bolt used in certain application with the strength of a bolt. High-strength steel bolts usually have a hexagonal head with an ISO strength rating (called property class ) stamped on the head. And the absence of marking/number indicates a lower grade bolt with low strength. The property classes most often used are 5.8, 8.8, and 10.9. The number before
15416-475: The United States are still inch based. The numbers stamped on the head of the bolt are referred to the grade of the bolt used in certain application with the strength of a bolt. High-strength steel bolts usually have a hexagonal head with an ISO strength rating (called property class ) stamped on the head. And the absence of marking/number indicates a lower grade bolt with low strength. The property classes most often used are 5.8, 8.8, and 10.9. The number before
15580-479: The angle at the tip of each of the 12 points (with a 90° angle on the XZN, instead of 60°) the general similarity and ability to insert the wrong tool can cause damage to the head. Triple-square drive fasteners have been used in high-torque applications, such as cylinder head bolts and drive train components. The fasteners involved have heads that are hardened and tempered to withstand the driving torque without destroying
15744-413: The bolt and should be conducted on actual fasteners rather than calculated. If a bolt is tensioned beyond the proof load, it may behave in plastic manner due to yielding in the threads and the tension preload may be lost due to the permanent plastic deformations. When elongating a fastener prior to reaching the yield point, the fastener is said to be operating in the elastic region; whereas elongation beyond
15908-413: The bolt and should be conducted on actual fasteners rather than calculated. If a bolt is tensioned beyond the proof load, it may behave in plastic manner due to yielding in the threads and the tension preload may be lost due to the permanent plastic deformations. When elongating a fastener prior to reaching the yield point, the fastener is said to be operating in the elastic region; whereas elongation beyond
16072-400: The bows screwed to the frame with 00-72 (pronounced double ought – seventy two) size screws. To calculate the major diameter of "ought" size screws count the number of 0's and multiply this number by 0.013 and subtract from 0.060. For example, the major diameter of a 000-72 screw thread is .060 – (3 x .013) = 0.060 − 0.039 = .021 inches. For most size screws there are multiple TPI available, with
16236-400: The bows screwed to the frame with 00-72 (pronounced double ought – seventy two) size screws. To calculate the major diameter of "ought" size screws count the number of 0's and multiply this number by 0.013 and subtract from 0.060. For example, the major diameter of a 000-72 screw thread is .060 – (3 x .013) = 0.060 − 0.039 = .021 inches. For most size screws there are multiple TPI available, with
16400-445: The coarse threads of a wood-screw or sheet-metal-screw threadform (but larger). The materials are usually carbon steel substrate with a coating of zinc galvanization (for corrosion resistance). The zinc coating may be bright yellow (electroplated), or dull gray ( hot-dip galvanized ). Bone screws have the medical use of securing broken bones in living humans and animals. As with aerospace and nuclear power, medical use involves some of
16564-445: The coarse threads of a wood-screw or sheet-metal-screw threadform (but larger). The materials are usually carbon steel substrate with a coating of zinc galvanization (for corrosion resistance). The zinc coating may be bright yellow (electroplated), or dull gray ( hot-dip galvanized ). Bone screws have the medical use of securing broken bones in living humans and animals. As with aerospace and nuclear power, medical use involves some of
16728-489: The cost of production of these parts. This will allow thinner materials to be used for the screws. The shorter head height allows more "Clearance for internal parts and more design flexibility". This allows the Mortorq drive to work in smaller and more complex builds. The recess and driver were designed for "full radial contact along all four wings of the screw" which helps to prevent stripping and cam-out. The straight walls in
16892-480: The design of the recess allow for almost all of the force of rotation to be used to drive the screw. When the bit is placed in the recess there is no wall contact until the driver is rotated, then there is full continuous contact to all four walls of the recess. The shallow recess allows for build-up and coating to occur without affecting the function of the driver. This shallow recess also grants off-angle drivability to allow work in hard-to-reach places. The design of
17056-437: The difficulties and expense of doing so at the time. In 1908, Canadian P. L. Robertson was the first to make the internal-wrenching square socket drive a practical reality by developing just the right design (slight taper angles and overall proportions) to allow the head to be stamped easily but successfully, with the metal cold forming as desired rather than being sheared or displaced in unwanted ways. Practical manufacture of
17220-437: The difficulties and expense of doing so at the time. In 1908, Canadian P. L. Robertson was the first to make the internal-wrenching square socket drive a practical reality by developing just the right design (slight taper angles and overall proportions) to allow the head to be stamped easily but successfully, with the metal cold forming as desired rather than being sheared or displaced in unwanted ways. Practical manufacture of
17384-479: The drawbacks of not fitting as closely as a hollow-ground screwdriver would, and increasing the possibility of damaging the fastener or surrounding area. ISO 2380-1 specifies the internationally standardized shape and dimensions of the tips of screwdrivers for slotted-head screws as well as the minimum test torque the blade-to-handle connection shall withstand. Screwdriver tips are generally designated by blade thickness × width in mm, e.g. 1.2 × 6.5 which roughly matches
17548-553: The electrical trade, particularly for device and circuit breaker terminals, as well as clamp connectors. Robertson screwdrivers are easy to use one-handed, because the tapered socket tends to retain the screw, even if it is shaken. They also allow for the use of angled screw drivers and trim head screws. The socket-headed Robertson screws reduce cam-out , stop a power tool when set, and can be removed if painted over or old and rusty. In industry, they speed up production and reduce product damage. [REDACTED] The LOX-Recess screw drive
17712-531: The first satisfactory screw-cutting lathe . The British engineer Henry Maudslay (1771–1831) gained fame by popularizing such lathes with his screw-cutting lathes of 1797 and 1800, containing the trifecta of leadscrew, slide rest, and change-gear gear train, all in the right proportions for industrial machining. In a sense he unified the paths of the Wyatts and Ramsden and did for machine screws what had already been done for wood screws, i.e., significant easing of production spurring commodification . His firm remained
17876-531: The first satisfactory screw-cutting lathe . The British engineer Henry Maudslay (1771–1831) gained fame by popularizing such lathes with his screw-cutting lathes of 1797 and 1800, containing the trifecta of leadscrew, slide rest, and change-gear gear train, all in the right proportions for industrial machining. In a sense he unified the paths of the Wyatts and Ramsden and did for machine screws what had already been done for wood screws, i.e., significant easing of production spurring commodification . His firm remained
18040-407: The head of tight screws, while a Pozidriv/Supadriv screwdriver will damage a Phillips screw. [REDACTED] A cross or double-slot screw drive, not a true cruciform drive in that the entire cross is not engaged, has two slots, perpendicular to each other, in the fastener head; a slotted screwdriver is used to drive either of the slots. This type is usually found in cheaply-made roofing bolts and
18204-409: The highest technology for fasteners; excellent performance, longevity, and quality are required, and reflected in prices. Bone screws are often made of relatively non-reactive stainless steel or titanium, and they often have advanced features such as conical threads, multistart threads, cannulation (hollow core), and proprietary screw drive types, some not seen outside of these applications. There are
18368-409: The highest technology for fasteners; excellent performance, longevity, and quality are required, and reflected in prices. Bone screws are often made of relatively non-reactive stainless steel or titanium, and they often have advanced features such as conical threads, multistart threads, cannulation (hollow core), and proprietary screw drive types, some not seen outside of these applications. There are
18532-479: The internal-wrenching hexagon drive ( hex socket ) shortly followed in 1911. In the early 1930s American Henry F. Phillips popularized the Phillips-head screw , with a cross-shaped internal drive. Later improved -head screws were developed, more compatible with screwdrivers not of the exactly right head size: Pozidriv and Supadriv . Phillips screws and screwdrivers are to some extent compatible with those for
18696-424: The internal-wrenching hexagon drive ( hex socket ) shortly followed in 1911. In the early 1930s American Henry F. Phillips popularized the Phillips-head screw , with a cross-shaped internal drive. Later improved -head screws were developed, more compatible with screwdrivers not of the exactly right head size: Pozidriv and Supadriv . Phillips screws and screwdrivers are to some extent compatible with those for
18860-442: The largest called PMT-7 can be used on screws with a head diameter of 35 mm. The Phillips Screw Company owns the licensed product that is the Mortorq spiral drive system. The Phillips Screw Company must inspect and approve any punches, bits, and screws before they are cleared for production. Along with this "all licensees must submit samples regularly to ensure that the strict quality standards are maintained". Solid modeling
19024-410: The letter M followed by the major diameter of the thread in millimetres (e.g. M8 ). If the thread does not use the normal coarse pitch (e.g. 1.25 mm in the case of M8), then the pitch in millimeters is also appended with a multiplication sign (e.g. "M8×1" if the screw thread has an outer diameter of 8 mm and advances by 1 mm per 360° rotation). The nominal diameter of a metric screw
19188-410: The letter M followed by the major diameter of the thread in millimetres (e.g. M8 ). If the thread does not use the normal coarse pitch (e.g. 1.25 mm in the case of M8), then the pitch in millimeters is also appended with a multiplication sign (e.g. "M8×1" if the screw thread has an outer diameter of 8 mm and advances by 1 mm per 360° rotation). The nominal diameter of a metric screw
19352-484: The letters "PH", plus a size code 0000, 000, 00, 0, 1, 2, 3, or 4 (in order of increasing size); the numerical bit size codes do not necessarily correspond to nominal screw size numbers. A Phillips screw head is slightly different from the later PoziDriv and Supadriv, similar at first glance. (see § Pozidriv for details) . The design is often criticized for its tendency to cam out at lower torque levels than other "cross head" designs. There has long been
19516-531: The like, where a thread of 5 mm (0.20 in) or above has a large flattened pan head . They provide some measure of redundancy: should one slot become deformed, the second may still be used. (Not to be confused with the company with a similar name, Philips ) [REDACTED] The Phillips screw drive (specified as an ANSI Type I Cross Recess and type H in ISO documentation) was created by John P. Thompson, who, after failing to interest manufacturers, sold his design to businessman Henry F. Phillips . Phillips
19680-483: The machinist happened to need on any given day). In 1821 Hardman Philips built the first screw factory in the United States – on Moshannon Creek, near Philipsburg – for the manufacture of blunt metal screws. An expert in screw manufacture, Thomas Lever, was brought over from England to run the factory. The mill used steam and water power, with hardwood charcoal as fuel. The screws were made from wire prepared by "rolling and wire drawing apparatus" from iron manufactured at
19844-483: The machinist happened to need on any given day). In 1821 Hardman Philips built the first screw factory in the United States – on Moshannon Creek, near Philipsburg – for the manufacture of blunt metal screws. An expert in screw manufacture, Thomas Lever, was brought over from England to run the factory. The mill used steam and water power, with hardwood charcoal as fuel. The screws were made from wire prepared by "rolling and wire drawing apparatus" from iron manufactured at
20008-405: The material and mechanical properties of imperial sized externally threaded fasteners. Some of the most common consensus standards for grades produced from carbon steels are ASTM A193, ASTM A307, ASTM A354, ASTM F3125, and SAE J429. Some of the most common consensus standards for grades produced from corrosion resistant steels are ASTM F593 & ASTM A193. The hand tool used to drive in most screws
20172-405: The material and mechanical properties of imperial sized externally threaded fasteners. Some of the most common consensus standards for grades produced from carbon steels are ASTM A193, ASTM A307, ASTM A354, ASTM F3125, and SAE J429. Some of the most common consensus standards for grades produced from corrosion resistant steels are ASTM F593 & ASTM A193. The hand tool used to drive in most screws
20336-632: The most common being designated a Unified Coarse Thread (UNC or UN) and Unified Fine Thread (UNF or UF). Note: In countries other than the United States and Canada, the ISO Metric Screw Thread System is primarily used today. Unlike most other countries the United States and Canada still use the Unified (Inch) Thread System. However, both are moving over to the ISO Metric System. It is estimated that approximately 60% of screw threads in use in
20500-449: The most common being designated a Unified Coarse Thread (UNC or UN) and Unified Fine Thread (UNF or UF). Note: In countries other than the United States and Canada, the ISO Metric Screw Thread System is primarily used today. Unlike most other countries the United States and Canada still use the Unified (Inch) Thread System. However, both are moving over to the ISO Metric System. It is estimated that approximately 60% of screw threads in use in
20664-644: The nail ends), forge welding , and many kinds of binding with cord made of leather or fiber, using many kinds of knots . The screw was one of the last of the simple machines to be invented. It first appeared in Mesopotamia during the Neo-Assyrian period (911-609) BC, and then later appeared in Ancient Egypt and Ancient Greece where it was described by the Greek mathematician Archytas of Tarentum (428–350 BC). By
20828-435: The nail ends), forge welding , and many kinds of binding with cord made of leather or fiber, using many kinds of knots . The screw was one of the last of the simple machines to be invented. It first appeared in Mesopotamia during the Neo-Assyrian period (911-609) BC, and then later appeared in Ancient Egypt and Ancient Greece where it was described by the Greek mathematician Archytas of Tarentum (428–350 BC). By
20992-502: The newer types, but with the risk of damaging the heads of tightly fastened screws. Threadform standardization further improved in the late 1940s, when the ISO metric screw thread and the Unified Thread Standard were defined. Precision screws, for controlling motion rather than fastening, developed around the turn of the 19th century, and represented one of the central technical advances, along with flat surfaces, that enabled
21156-436: The newer types, but with the risk of damaging the heads of tightly fastened screws. Threadform standardization further improved in the late 1940s, when the ISO metric screw thread and the Unified Thread Standard were defined. Precision screws, for controlling motion rather than fastening, developed around the turn of the 19th century, and represented one of the central technical advances, along with flat surfaces, that enabled
21320-444: The point is the ultimate tensile strength in MPa divided by 100. The number after the point is the multiplier ratio of yield strength to ultimate tensile strength. For example, a property class 5.8 bolt has a nominal (minimum) ultimate tensile strength of 500 MPa, and a tensile yield strength of 0.8 times ultimate tensile strength or 0.8 (500) = 400 MPa. Ultimate tensile strength
21484-399: The point is the ultimate tensile strength in MPa divided by 100. The number after the point is the multiplier ratio of yield strength to ultimate tensile strength. For example, a property class 5.8 bolt has a nominal (minimum) ultimate tensile strength of 500 MPa, and a tensile yield strength of 0.8 times ultimate tensile strength or 0.8 (500) = 400 MPa. Ultimate tensile strength
21648-472: The recess and shorter head height allows for more aesthetically pleasing work. This is in hopes that it will enhance the beauty and style of a product. Instead of covering up the screw head that it serves as an aesthetic part of the design. Ten different recess sizes are available for the Mortorq. The smallest of these, the PMT-000 can be used with screws that have a head diameter as small as 2.5 mm. While
21812-399: The relationship given in these standards between the thread size and the maximum width across the hexagonal flats (wrench size): In addition, the following non-preferred intermediate sizes are specified: Bear in mind that these are just examples and the width across flats is different for structural bolts, flanged bolts, and also varies by standards organization. The first person to create
21976-399: The relationship given in these standards between the thread size and the maximum width across the hexagonal flats (wrench size): In addition, the following non-preferred intermediate sizes are specified: Bear in mind that these are just examples and the width across flats is different for structural bolts, flanged bolts, and also varies by standards organization. The first person to create
22140-418: The rolling process does not cut the grain of the metal. A self-tapping screw is designed to cut its own thread, usually in a fairly soft metal or plastic, in the same way as a wood screw (wood screws are actually self-tapping, but not referred to as such). ASME standards specify a variety of machine screws (aka stove bolts ) in diameters ranging up to 0.75 in (19.05 mm). A machine screw or bolt
22304-418: The rolling process does not cut the grain of the metal. A self-tapping screw is designed to cut its own thread, usually in a fairly soft metal or plastic, in the same way as a wood screw (wood screws are actually self-tapping, but not referred to as such). ASME standards specify a variety of machine screws (aka stove bolts ) in diameters ranging up to 0.75 in (19.05 mm). A machine screw or bolt
22468-498: The same diameter and pitch as ISO M6, the threads have different forms and are not compatible. BA threads are still common in some niche applications. Certain types of fine machinery, such as moving-coil meters and clocks, tend to have BA threads wherever they are manufactured. BA sizes were also used extensively in aircraft, especially those manufactured in the United Kingdom. BA sizing is still used in railway signalling, mainly for
22632-441: The same diameter and pitch as ISO M6, the threads have different forms and are not compatible. BA threads are still common in some niche applications. Certain types of fine machinery, such as moving-coil meters and clocks, tend to have BA threads wherever they are manufactured. BA sizes were also used extensively in aircraft, especially those manufactured in the United Kingdom. BA sizing is still used in railway signalling, mainly for
22796-748: The sharp tapered point on nearly all modern wood screws. Some wood screws were made with cutting dies as early as the late 1700s (possibly even before 1678 when the book content was first published in parts). Eventually, lathes were used to manufacture wood screws, with the earliest patent being recorded in 1760 in England. During the 1850s, swaging tools were developed to provide a more uniform and consistent thread. Screws made with these tools have rounded valleys with sharp and rough threads. Once screw turning machines were in common use, most commercially available wood screws were produced with this method. These cut wood screws are almost invariably tapered, and even when
22960-698: The sharp tapered point on nearly all modern wood screws. Some wood screws were made with cutting dies as early as the late 1700s (possibly even before 1678 when the book content was first published in parts). Eventually, lathes were used to manufacture wood screws, with the earliest patent being recorded in 1760 in England. During the 1850s, swaging tools were developed to provide a more uniform and consistent thread. Screws made with these tools have rounded valleys with sharp and rough threads. Once screw turning machines were in common use, most commercially available wood screws were produced with this method. These cut wood screws are almost invariably tapered, and even when
23124-417: The similar naming scheme to metric fasteners, there is no correlation between the name of the size and the dimensions of the tool. Some sizes (at least M14, M16, M18) are also available in a tamperproof version (with a center hole) The 12-pointed internal star shape superficially resembles the "double hex" fastener head but differs subtly in that the points are shaped to an internal angle of 90° (derived from
23288-495: The size is given as a fraction; for sizes less than this an integer is used, ranging from 0 to 16. The integer sizes can be converted to the actual diameter by using the formula 0.060 + (0.013 × number). For example, a #4 screw is 0.060 + (0.013 × 4) = 0.060 + 0.052 = 0.112 inches in diameter. There are also screw sizes smaller than "0" (zero or ought). The sizes are 00, 000, 0000 which are usually referred to as two ought, three ought, and four ought. Most eyeglasses have
23452-495: The size is given as a fraction; for sizes less than this an integer is used, ranging from 0 to 16. The integer sizes can be converted to the actual diameter by using the formula 0.060 + (0.013 × number). For example, a #4 screw is 0.060 + (0.013 × 4) = 0.060 + 0.052 = 0.112 inches in diameter. There are also screw sizes smaller than "0" (zero or ought). The sizes are 00, 000, 0000 which are usually referred to as two ought, three ought, and four ought. Most eyeglasses have
23616-563: The sizes were actually defined in metric terms, a 0BA thread having a 6 mm diameter and 1 mm pitch. Other threads in the BA series are related to 0BA in a geometric series with the common factors 0.9 and 1.2. For example, a 4BA thread has pitch p = 0.9 4 {\displaystyle \scriptstyle p=0.9^{4}} mm (0.65 mm) and diameter 6 p 1.2 {\displaystyle \scriptstyle 6p^{1.2}} mm (3.62 mm). Although 0BA has
23780-518: The sizes were actually defined in metric terms, a 0BA thread having a 6 mm diameter and 1 mm pitch. Other threads in the BA series are related to 0BA in a geometric series with the common factors 0.9 and 1.2. For example, a 4BA thread has pitch p = 0.9 4 {\displaystyle \scriptstyle p=0.9^{4}} mm (0.65 mm) and diameter 6 p 1.2 {\displaystyle \scriptstyle 6p^{1.2}} mm (3.62 mm). Although 0BA has
23944-403: The slot; this often causes damage to the screw and surrounding material. For this reason, cruciform-slotted along with drives have replaced the slot drive in numerous applications. The tool used to drive a slot is called a common blade , flat-blade , slot-head , flat-tip or flat-head / flathead screwdriver. A hollow-ground screwdriver is less likely to cam out (leave the slot due to
24108-477: The star points. They are commonly found on German vehicles such as BMW , Opel , Mercedes , and those from the Volkswagen Group ( Porsche , Audi , Seat , Skoda , and Volkswagen ). Screw The screw head on one end has a milled slot that commonly requires a tool to transfer the twisting force. Common tools for driving screws include screwdrivers , wrenches , coins and hex keys . The head
24272-426: The tapered shank is not obvious, they can be discerned because the threads do not extend past the diameter of the shank. Such screws are best installed after drilling a pilot hole with a tapered drill bit. The majority of modern wood screws, except for those made of brass, are formed on thread rolling machines. These screws have a constant diameter and threads with a larger diameter than the shank and are stronger because
24436-426: The tapered shank is not obvious, they can be discerned because the threads do not extend past the diameter of the shank. Such screws are best installed after drilling a pilot hole with a tapered drill bit. The majority of modern wood screws, except for those made of brass, are formed on thread rolling machines. These screws have a constant diameter and threads with a larger diameter than the shank and are stronger because
24600-481: The termination of electrical equipment and cabling. BA threads are extensively used in Model Engineering where the smaller hex head sizes make scale fastenings easier to represent. As a result, many UK Model Engineering suppliers still carry stocks of BA fasteners up to typically 8BA and 10BA. 5BA is also commonly used as it can be threaded onto 1/8 rod. The Unified Thread Standard (UTS) is most commonly used in
24764-421: The termination of electrical equipment and cabling. BA threads are extensively used in Model Engineering where the smaller hex head sizes make scale fastenings easier to represent. As a result, many UK Model Engineering suppliers still carry stocks of BA fasteners up to typically 8BA and 10BA. 5BA is also commonly used as it can be threaded onto 1/8 rod. The Unified Thread Standard (UTS) is most commonly used in
24928-717: The tool. Both the tool and the socket have a slight taper . Originally to make the manufacture of the screws practical using cold forming of the heads, this taper provides two other advantages which have served to popularize the drive: it makes inserting the tool easier, and tends to help keep the screw on the tool tip without the user needing to hold it there. Robertson screws are commonplace in Canada , though they have been used elsewhere and have become much more common in other countries. As patents expired and awareness of their advantages spread, Robertson fasteners have become popular in woodworking and in general construction. Combinations of Robertson/Phillips/slot drives are often used in
25092-501: The top of the head. Because of this, a regular Phillips or flat-blade screwdriver will not fit the head. It is used in military and aerospace applications, for example, the Boeing E-3 Sentry , Lockheed P-3 Orion , Lockheed SR-71 Blackbird , General Dynamics F-16 Fighting Falcon , Airbus , Embraer , and Bombardier Inc. aircraft. Phillips Screw Company owns the name and produces the fasteners. The applicable standards that govern
25256-454: The torque being translated into an axial force, similar to that encountered with Phillips drive but dependent only on driver blade), so more torque can be applied without damaging the screw head. Flat-blade jeweler's screwdrivers and the tips found in 1 ⁄ 4 -inch or 6.4-millimeter drive sets are generally hollow-ground. Note that it is this typical chisel shape which allows 9 screwdriver sizes to drive 24 different slotted screw sizes, with
25420-406: The yield point is referred to as operating in the plastic region of the bolt material. If a bolt is loaded in tension beyond its proof strength, the yielding at the net root section of the bolt will continue until the entire section begins to yield and it has exceeded its yield strength. If tension increases, the bolt fractures at its ultimate strength. Mild steel bolts have property class 4.6, which
25584-406: The yield point is referred to as operating in the plastic region of the bolt material. If a bolt is loaded in tension beyond its proof strength, the yielding at the net root section of the bolt will continue until the entire section begins to yield and it has exceeded its yield strength. If tension increases, the bolt fractures at its ultimate strength. Mild steel bolts have property class 4.6, which
25748-405: Was 55°, and the depth and pitch varied with the diameter of the thread (i.e., the bigger the bolt, the coarser the thread). Spanners for Whitworth bolts are marked with the size of the bolt, not the distance across the flats of the screw head. The most common use of a Whitworth pitch nowadays is in all UK scaffolding . Additionally, the standard photographic tripod thread, which for small cameras
25912-405: Was 55°, and the depth and pitch varied with the diameter of the thread (i.e., the bigger the bolt, the coarser the thread). Spanners for Whitworth bolts are marked with the size of the bolt, not the distance across the flats of the screw head. The most common use of a Whitworth pitch nowadays is in all UK scaffolding . Additionally, the standard photographic tripod thread, which for small cameras
26076-433: Was able to create a shorter head height compared to other screws at the time of its development, which in turn reduced the weight of this drive type. The Mortorq was originally designed for aerospace applications. This reduction of weight within the head height was able to create lighter assemblies for many aerospace projects. The materials used in aerospace applications are expensive, and the reduction of weight cuts down on
26240-405: Was invented by Brad Wagner, and fasteners using it are distributed by licensees Hitachi, Dietrick Metal Framing, and Grabber. The design is four overlapping square recesses, with 12 contact points, and is designed to tolerate more torque, decrease wear, and avoid cam-out. [REDACTED] The double-square drive is two squares superimposed at 45° rotation, forming an eight-pointed star. The design
26404-501: Was not quickly completed; it has been an evolving process ever since. Further improvements to the mass production of screws continued to push unit prices lower and lower for decades to come, throughout the 19th century. The mass production of wood screws (metal screws for fixing wood) in a specialized, single-purpose, high-volume-production machine tool; and the low-count, toolroom -style production of machine screws or bolts (V-thread) with easy selection among various pitches (whatever
26568-501: Was not quickly completed; it has been an evolving process ever since. Further improvements to the mass production of screws continued to push unit prices lower and lower for decades to come, throughout the 19th century. The mass production of wood screws (metal screws for fixing wood) in a specialized, single-purpose, high-volume-production machine tool; and the low-count, toolroom -style production of machine screws or bolts (V-thread) with easy selection among various pitches (whatever
26732-477: Was patented by GKN Screws and Fasteners in 1962. It was designed to allow more torque to be applied and greater engagement than Phillips drives. As a result, the Pozidriv is less likely to cam out . It is similar to, and compatible with, the Supadriv screw drive. Pozidriv screwdrivers are often designated using the letters "PZ" followed by a size code of 0, 1, 2, 3, 4 or 5 (in order of increasing size). The numbers do not correspond to nominal screw size numbers. PZ1
26896-531: Was put into bankruptcy in 1987 and liquidated in 1990. Another entity called Reed & Prince Manufacturing Corporation, now of Leominster, Massachusetts, purchased some of the assets including the name at the liquidation sale. As of 2022, both Frearson screws and Frearson bits are readily available in several sizes. The available screws are made of silicon bronze . [REDACTED] Also called BNAE NFL22-070 after its Bureau de normalisation de l'aéronautique et de l'espace standard number. A cross-head screw with
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