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At a minimum, a
screw A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...
drive is a set of shaped cavities and protrusions on the screw head that allows
torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
to be applied to it. Usually, it also involves a mating
tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...
, such as a
screwdriver A screwdriver is a tool, manual or powered, used for turning screws. A typical simple screwdriver has a handle and a shaft, ending in a tip the user puts into the screw head before turning the handle. This form of the screwdriver has been repla ...
, that is used to turn it. The following heads are categorized based on frequency, with some of the less-common drives being classified as "tamper-resistant." Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00". These sizes do not necessarily describe a particular dimension of the drive shape, but rather are arbitrary designations.


Slotted drives


Slot

Slot screw drives have a single horizontal indentation (the ''slot'') in the fastener head and is driven by a "common blade" or flat-bladed
screwdriver A screwdriver is a tool, manual or powered, used for turning screws. A typical simple screwdriver has a handle and a shaft, ending in a tip the user puts into the screw head before turning the handle. This form of the screwdriver has been repla ...
. This form was the first type of screw drive to be developed, and for centuries, it was the simplest and cheapest to make. Additionally, it is unique compared to other common drives, due to it being straightforward to manufacture the slot head, and the ability to be driven by a simple handtool. The ''slotted screw'' is commonly found in existing products and installations, along with use in simple
carpentry Carpentry is a skilled trade and a craft in which the primary work performed is the cutting, shaping and installation of building materials during the construction of buildings, ships, timber bridges, concrete formwork, etc. Carpenters tr ...
work and in applications where minimal
torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
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 tool A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labor used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed ...
s, given that a power driver often slips out of 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 Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
(leave the slot due to 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 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 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 a classic North American 1/4" 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 a slot drive.


Coin-slot

Coin-slot drives are so-called because of the curved bottom of the recess, which facilitates driving them with a suitable
coin A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order t ...
. 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.


Hi-Torque

Hi-Torque slot drives were designed by Alcoa Fastening Systems, for situations where very high torque 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.


Cross

A ''cross'' or ''double-slot'' screw drive has two slots, oriented perpendicular to each other, in the fastener head; a slotted screwdriver is still used to drive just one of the slots. This type is usually found in cheaply-made roofing bolts and the like, where a thread of or above has a large flattened
pan head Pan Head (born Anthony Johnson, 1966, Saint Mary Parish, Jamaica, died October 10th, 1993, Marverly, St. Andrew) was a ragga/ dancehall deejay. Biography Pan Head emerged in 1985, and after working for several years with the ''Love Vibration'' ...
. The advantage is that they provide some measure of redundancy: should one slot be deformed in service, the second may still be used.


Cruciform drives

The following are screw drives based on a
cruciform Cruciform is a term for physical manifestations resembling a common cross or Christian cross. The label can be extended to architectural shapes, biology, art, and design. Cruciform architectural plan Christian churches are commonly described ...
shape; i.e., a cross shape. Other names for these types of drives are ''cross recessed'', ''cross-head'', ''cross tip'', and ''cross-point''. A double slotted screw drive is not considered cruciform because the shape is not recessed, and consists only of two superimposed simple milled slots. Some of these types are specified in ISO 4757, ''Cross recesses for screws''.


Phillips

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 Henry Frank Phillips (June 4, 1889 – April 13, 1958) was an American businessman from Portland, Oregon. The Phillips-head ("crosshead") screw and screwdriver are named after him. The importance of the crosshead screw design lies in its self-ce ...
. Phillips is credited with forming a company (
Phillips Screw Company Phillips may refer to: Businesses Energy * Chevron Phillips Chemical, American petrochemical firm jointly owned by Chevron Corporation and Phillips 66. * ConocoPhillips, American energy company * Phillips 66, American energy company * Philli ...
), 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 American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
of
Providence, Rhode Island Providence is the capital and most populous city of the U.S. state of Rhode Island. One of the oldest cities in New England, it was founded in 1636 by Roger Williams, a Reformed Baptist theologian and religious exile from the Massachusetts Bay ...
, was responsible for devising a means of efficiently manufacturing the screw, and successfully patented and licensed their method; other screw makers of 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 Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
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 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 significantly different from a PoziDriv; see section below for details. The design is often criticized for its tendency to
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
at lower torque levels than other "cross head" designs. There has long been a popular belief that this was a ''deliberate'' feature of the design, to assemble aluminium aircraft without overtightening the fasteners. Extensive evidence is lacking for this specific narrative, and the feature is not mentioned in the original patents. However, a 1949 refinement to the original design described in US Patent #2,474,994 describes this feature.


Pozidriv

The ''Pozidriv,'' sometimes incorrectly spelled "Pozidrive", is an improved version of the Phillips screw drive. It is designated "Type IA" by
ANSI The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
standards. and "Type Z" in ISO documents. The Pozidriv was patented by
GKN GKN Ltd is a British multinational automotive and aerospace components business headquartered in Redditch, England. It is a long-running business known for many decades as Guest, Keen and Nettlefolds. It can trace its origins back to 1759 an ...
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 Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
.Pozidriv page
at Phillips Screw Company
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 is normally used on screw diameters from 2-3mm, PZ2 from 3.5-5mm and PZ3 from 5.5mm to 8mm. 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, 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. The manufacturing process for Pozidriv screwdriver bits requires a slightly more complex cutter than that for Phillips, however both can be manufactured in four cuts from a tapered blank. Pozidriv and Phillips appear broadly interchangeable, but may cause damage if incorrectly used. Pozidriv screwdrivers will jam fit into Phillips screws, but when tightened they may slip or tear out 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 screwdriver.


JIS B 1012

The '' JIS B 1012'' is commonly found in Japanese made equipment, such as cameras and motorbikes. Superficially it looks like a Phillips screw with narrower and more vertical slots, to give less tendency to
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
. 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 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. "JIS" standardized cruciform-blade screwdrivers are available for this type of screw, and should always be used to avoid head and driver damage.


Supadriv

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 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, the Supadriv screwhead is similar to Pozidriv but has only two identification ticks, and the secondary blades are larger. Drive blades are about equal thickness. The main practical difference is in driving screws into vertical surfaces: that close to a near-vertical surface to drive the screws into the drivers, Supadriv has superior bite, making screwdriving more efficient, with less
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
.


Phillips II

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 a stick-fit, and to provide anti cam-out properties (the ribs are trademarked as "ACR" for Anti Cam-out Ribs).


Frearson

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 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 Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
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, 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 Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
.


French recess

upFrench recess driver bit frameless, x22px, alt= Also called ''BNAE NFL22-070'' after its Bureau de normalisation de l'aéronautique et de l'espace standard number. A cross-head screw with a two-step driver design, with the blade diameter stepping up at a distance from the point.


Mortorq

frameless, x22px, alt= 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 was able to create a shorter head height compared to other screws at the time of its development. This shorter head height was able to reduce 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 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.


Design and Application

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 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 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 2.5mm. While the largest called PMT-7 can be used on screws with a head diameter of 35mm.


Quality Assurance

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 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. For the Phillips Screw Company, consistency is key.


Square drives


Robertson

A
Robertson screw A Robertson screw, also known as a square screw or Scrulox, is a type of screw with a square-shaped socket in the screw head and a corresponding square protrusion on the tool. Both the tool and socket have a slight taper. Originally designed to ...
, also known as a ''square'' or ''Scrulox'' screw drive, is specified as ANSI Type III Square Center and has a
square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length adj ...
-shaped socket in the screw head and a square protrusion on the tool. Both the tool and the socket have a slight
taper Taper may refer to: * Part of an object in the shape of a cone (conical) * Taper (transmission line), a transmission line gradually increasing or decreasing in size * Fishing rod taper, a measure of the flexibility of a fishing rod * Conically ta ...
. Originally to make the manufacture of the screws practical using
cold forming In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot roll ...
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 Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, 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 Woodworking is the skill of making items from wood, and includes cabinet making (cabinetry and furniture), wood carving, woodworking joints, joinery, carpentry, and woodturning. History Along with Rock (geology), stone, clay and animal parts, ...
and in general construction. Combinations of Robertson/Phillips/slot drives are often used in 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 Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
, 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.


Multiple-square drives


LOX-Recess

The LOX-Recess screw drive 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 increase torque, decrease wear, and avoid cam-out.


Double-square

The ''double-square'' drive is two squares superimposed at 45° rotation, forming an 8-pointed star. The design is similar to a square drive (Robertson), but can be engaged at more frequent angles by the driver bit.


Triple-square (XZN)

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 Robertson may refer to: People * Robertson (surname) (includes a list of people with this name) * Robertson (given name) * Clan Robertson, a Scottish clan * Robertson, stage name of Belgian magician Étienne-Gaspard Robert (1763–1837) Places ...
squares are superimposed at 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, M8, M9, M10, M12, M14, M16, and M18. Despite the similar naming scheme to
metric Metric or metrical may refer to: * Metric system, an internationally adopted decimal system of measurement * An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement Mathematics In mathem ...
fasteners, there is no correlation between the name of the size and the dimensions of the tool. 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 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 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 In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
bolts and
drive train A drivetrain (also frequently spelled as drive train or sometimes drive-train) is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drivetrain is the components o ...
components. The fasteners involved have heads that are hardened and tempered to withstand the driving torque without destroying the star points. They are commonly found on
German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...
vehicles A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wate ...
such as BMW,
Opel Opel Automobile GmbH (), usually shortened to Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by the American automaker General Motors from 1929 until 2017 and the PSA Grou ...
, Mercedes, and those from the
Volkswagen Group Volkswagen AG (), known internationally as the Volkswagen Group, is a German multinational automotive manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. The company designs, manufactures and distributes passenger and commercial ...
(
Porsche Dr. Ing. h.c. F. Porsche AG, usually shortened to Porsche (; see #Pronunciation, below), is a German automobile manufacturer specializing in high-performance sports cars, SUVs and sedans, headquartered in Stuttgart, Baden-Württemberg, Germany ...
,
Audi Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide. Th ...
,
Seat A seat is a place to sit. The term may encompass additional features, such as back, armrest, head restraint but also headquarters in a wider sense. Types of seat The following are examples of different kinds of seat: * Armchair (furniture), ...
,
Skoda Škoda means ''pity'' in the Czech and Slovak languages. It may also refer to: Czech brands and enterprises * Škoda Auto, automobile and previously bicycle manufacturer in Mladá Boleslav ** Škoda Motorsport, the division of Škoda Auto respons ...
, and
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
).


Internal hex drives


Hex socket

The ''hex socket'' screw drive has a hexagonal recess and may be driven by a ''hex wrench'', also known as an ''Allen wrench'', ''Allen key'', ''
hex key Hex keys of various sizes Socket head screws of various sizes A hex key (also, hex wrench, Allen key and Allen wrench) is a simple driver for bolts or screws that have heads with ''internal'' hexagonal recesses (sockets). Hex keys are form ...
'', or ''inbus'' as well as by a hex screwdriver (also known as a hex driver) or bit. Tamper-resistant versions with a pin in the recess are available. Metric sizes of the hex socket are defined by ISO 4762 (socket head cap screws), ISO 4026 (socket set screws with flat point), ISO 4027 (socket set screws with cone point), ISO 4028 (socket set screws with dog point), and ISO 4029 (socket set screws with cup point). The German company Bauer & Schaurte patented the hex socket 1936 in Germany, and marketed products based on it. The term "inbus" is derived from ''Innensechskant Bauer u. Schaurte'' (German: "Inner 6-edge Bauer & Schaurte"), analogous to the US term "Allen key". In many countries it is commonly but incorrectly called "imbus".


Double hex

''Double hex'' is a screw drive with a socket shaped as two coaxial offset hex recesses; it can be driven by standard hex key tools. The shape resembles triple square and spline screw drives, but they are incompatible. The radial "height" of each
arris In architecture, an arris is the sharp edge formed by the intersection of two surfaces, such as the corner of a masonry unit; the edge of a timber in timber framing; the junction between two planes of plaster or any intersection of divergent a ...
is reduced, compared to a six-point, although their number is doubled. They are potentially capable of allowing more torque than a six-point, but greater demands are placed on the metallurgy of the heads and the tools used, to avoid rounding off and slippage. The shape of a double hex head is equivalent to that of a 2 regular
dodecagram In geometry, a dodecagram (γραμμή
Henry George Liddell, Robe ...
.


Pentalobular sockets


Pentalobe

The ''pentalobe'' screw drive (often mistaken for 6-point torx screw drives) is a five-pointed tamper-resistant system being implemented by
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
in its products. Apple's first use of the pentalobe drive was in mid-2009 to secure the battery in the MacBook Pro. Smaller versions are now used on the
iPhone 4 The iPhone 4 is a smartphone that was designed and marketed by Apple Inc. It is the fourth generation of the iPhone lineup, succeeding the iPhone 3GS and preceding the 4S. Following a number of notable leaks, the iPhone 4 was first unvei ...
and subsequent models, the
MacBook Air The MacBook Air is a line of ultrabook computers developed and manufactured by Apple Inc. It consists of a full-size keyboard, a machined aluminum case, and, in the more modern versions, a thin light structure. The Air was originally positioned ...
(since the late 2010 model), the MacBook Pro with Retina Display and the 2015 MacBook. Inexpensive pentalobe screwdrivers, manufactured by third parties, are relatively easy to obtain. Pentalobe screw sizes include TS1 (also known as P2 or 0.8 mm, used on the iPhone 4 and subsequent models), TS4 (also known as P5 or 1.2 mm, used on the MacBook Air ince late 2010 the MacBook Pro with Retina Display and the 2015 MacBook) and TS5 (also known as P6 or 1.5 mm, used on the 2009 MacBook Pro battery). The TS designation is ambiguous as it is also used for a Torq-set screw drive.


ASTER recess

The ''ASTER recess'' was designed by LISI Aerospace to provide a more reliable solution than the hexagonal recess for assemblies of composite structures on aircraft. This recess is optimized to fit on the threaded end of aerospace fasteners. These fasteners allow for tightening the nut and holding the bolt simultaneously, on the same side of the structure, by only one operator.


Hexalobular (Torx)


Torx

The ''hexalobular socket'' screw drive, often referred to by the original proprietary brand name ''
Torx Torx (pronounced ) is a trademark for a type of screw drive characterized by a 6-point star-shaped pattern, developed in 1967, Bernard F. Reiland, "Coupling arrangement and tools for same", filed 1967-03-21 by Camcar Textron. A popular generic ...
'' () or by the alternative generic name ''star drive'', uses a star-shaped recess in the fastener with six rounded points. It was designed to permit increased torque transfer from the driver to the bit compared to other drive systems. The drive was developed in 1967 by Camcar
Textron Textron Inc. is an American industrial conglomerate based in Providence, Rhode Island. Textron's subsidiaries include Arctic Cat, Bell Textron, Textron Aviation (which itself includes the Beechcraft, and Cessna brands), and Lycoming Engines. ...
. Torx is very popular in the automotive and electronics industries because of resistance to
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
, and extended bit life, as well as reduced operator fatigue by minimizing the need to bear down on the drive tool to prevent cam out. A tamper-resistant '' Security Torx'' head has a small pin inside the recess. Owing to its six-fold symmetry, a Torx driver can also be used as an improvised substitute for a hex driver, although careful sizing is critical to prevent stripping the socket.


Torx Plus

''Torx Plus'' is an improved version of Torx that extends tool life even further and permits greater torque transfer compared to Torx. An ''External Torx'' version exists, where the screw head has the shape of a Torx screwdriver bit, and a Torx socket is used to drive it.


Torx Plus Tamper-Resistant

The tamper-resistant variant of Torx Plus, sometimes called ''Torx Plus Security'', is a five-lobed variant, with a center post. It is used for security as the drivers are uncommon.


Torx Paralobe

''Torx Paralobe'' is a further improvement over Torx Plus, claiming 40% increased drive system torque over Torx and 20% over Torx Plus.


Torx ttap

''Torx ttap'' is a version of Torx that reduces wobbling between the fastener and the tool, and is
backward compatible Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
with standard hexalobular tools.


Spline socket

The ''spline socket'' (alternatively known as ''Bristo'',Radio Material School, Naval Research Laboratory. (1943)
NAVPERS 14004 ''Mechanical Practice''
Washington, D.C.: USGPO. pp. 48, 50, 51.
''Bristol'',Bureau of Naval Personnel. (1971)
''Tools and Their Uses''
Washington, D.C.: USGPO. p. 13 (21)
''Bristol spline'', ''multiple-spline''The Bristol Company (June 18, 1962
"Why a Multiple-Spline Socket Screw?"
New York: C.M. Business Publications Inc. ''Purchasing''. p. 137
and ''fluted'') screw drive features four or six splines.American Society of Mechanical Engineers (2003). ASME B18.3-2003 ''Socket Cap, Shoulder, and Set Screws, Hex and Spline Keys (Inch Series)''. New York: ASME. pp. 42, 45 Almost all of the force of the key or driver is applied normal to the sides of the splines. Little force tending to expand the socket is exerted, unlike the hexagon socket design, making the spline socket preferable for fasteners made of lower strength materials and in setscrews due to reduced tendency of the setscrew to bind.United States Maritime Service Institute. (1949)
''Engine Room Tools''
New York: Mast Magazine Association. p. 25
The spline socket is also preferred over the hexagon socket in screws that must be subjected to high driving torque and in applications requiring high reliability of the fastener. Compared to the hexagon socket drive, spline socket drives are less likely to strip for the same amount of torque; however, the spline socket drive is not much more strip-resistant than a Torx drive. As a makeshift if the correct spline key is not available, a spline socket screw can be turned with any screwdriver designed to drive slotted screws that fits into the socket such that the width of the blade occupies the major diameter of the socket and the thickness of the blade permits it to fit between adjacent splines.Editors (April, May 1913)
"Goodwin's Hollow Safety Set Screw"
''Hardware Dealers' Magazine''. pp. 846 V, 865, 1090
This makeshift does not permit as much torque to be applied to the screw as can be applied with the correct spline key, due to concentration of stress that can damage the socket or screwdriver. The spline socket drive system was patented in the United States in 1913 by Dwight S. Goodwin and initially produced by the Goodwin Hollow Set Screw Company. Spline socket screws are used in
avionics Avionics (a blend word, blend of ''aviation'' and ''electronics'') are the Electronics, electronic systems used on aircraft. Avionic systems include communications, Air navigation, navigation, the display and management of multiple systems, ...
, high reliability applications, cameras, air brakes, construction and farm equipment and astronomy equipment.


Combination drives

Some screws have heads designed to accommodate more than one kind of driver, sometimes referred to as combo-head or combi-head. The most common of these are a combination of a ''slotted/Phillips'' head. Other combinations are a Phillips and Robertson, a Robertson and a slotted, a Torx and a slotted and a triple-drive screw that can take a slotted, Phillips or a Robertson.


Slotted/Phillips

The ''Slotted/Phillips'' head is often used in attaching knobs to furniture drawer fronts and combined ''slotted/pozidriv'' heads are so ubiquitous in electrical switchgear to have earned the nickname "electrician's screws". (The idea is that first screwdriver out of the toolbox is used, and the user does not have to waste valuable time searching for the correct driver). Slotted/Phillips (as opposed to slotted/pozidriv) heads occur in some North American-made switchgear. Their rise to popular use has been in spite of the fact that the head is weaker and neither a flat screwdriver nor a Pozidriv/Phillips screwdriver as appropriate is fully successful in driving these screws to the required torque. Some screwdriver manufacturers solve this problem offer matching screwdrivers and call them "Modulo", "plus-minus", or "contractor screwdrivers", although the original concept of not needing to search for a particular driver is defeated.


ACR Phillips II Plus

ACR Phillips II Plus is a screw-drive design that can be driven by a #2 Phillips driver or a #2 Robertson driver, but when driven by a Phillips II Plus Bit, the combination results in a stick-fit interface.


Phillips/square

The ''Phillips/square'' screw drive, also known as the ', ''Pozisquare'' screw drive, is a combination of the Phillips and Robertson screw drives. While a standard Phillips or Robertson tool can be used, there is also a dedicated tool for it that increases the surface area between the tool and the fastener so it can handle more torque.


Recex

The ''Recex'' drive system claims it offers the combined non-slip convenience of a Robertson drive during production assembly and Phillips for after market serviceability. The Phillips Screw Company offers both Phillips and Pozidriv combo heads with Robertson.


Slotted/Torx

A combined slotted and Torx drive screw was used in electronics manufacturing. For example,
Compaq Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
used this type to combine the benefits of Torx in manufacturing and the commonality of flat drive in field repair situations. The slot was closed on the ends to prevent the flat-blade tool from slipping out sideways and damaging nearby electronics.


Slotted/Square

Also known as an ECX or Combination Tip drive. A combined slotted and Robertson drive screw found in electrical power equipment and distribution equipment. The design allows for higher torque application with reduced camming, slipping out and damaging the fastener.


Clutch

There are two types of ''clutch'' screw drives: Type A and Type G. Type A, also known as a "standard clutch", resembles a
bow tie The bow tie is a type of necktie. A modern bow tie is tied using a common shoelace knot, which is also called the bow knot for that reason. It consists of a ribbon of fabric tied around the collar of a shirt in a symmetrical manner so that th ...
, with a small circular "knot" at the center. These were common in GM automobiles, trucks and buses of the 1940s and 1950s. Type G resembles a butterfly, and lacks the center "knot". This type of screw head is commonly used in the manufacture of
mobile homes A mobile home (also known as a house trailer, park home, trailer, or trailer home) is a prefabricated structure, built in a factory on a permanently attached chassis before being transported to site (either by being towed or on a trailer). Us ...
and
recreational vehicles A recreational vehicle, often abbreviated as RV, is a motor vehicle or trailer that includes living quarters designed for accommodation. Types of RVs include motorhomes, campervans, coaches, caravans (also known as travel trailers and camper ...
. The clutch head was designed to be driven with a flat-blade screwdriver as well as a clutch driver.


Thumbscrew

A ''thumbscrew'' is a type of screw drive with either a tall head and ridged or
knurl Knurling is a manufacturing process, typically conducted on a lathe, whereby a pattern of straight, angled or crossed lines is rolled into the material. Etymology The terms ''knurl'' and ''knurled'' are from an earlier ''knur'' ‘knot in wo ...
ed sides, or a key-like flat-sided vertical head. They are intended to be tightened and loosened by hand, and not found in structural applications. They are sometimes also cut for
Phillips head Henry Frank Phillips (June 4, 1889 – April 13, 1958) was an American businessman from Portland, Oregon. The Phillips-head ("crosshead") screw and screwdriver are named after him. The importance of the crosshead screw design lies in its self-ce ...
or slotted screwdrivers as well as having the knurl for finger grip.
ASME The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing ...
18.6.8 covers dimensions for Type A (shoulder under the head), regular and heavy, along with Type B (without shoulder), regular and heavy. They can be found on many
computer case A computer case, also known as a computer chassis, is the enclosure that contains most of the hardware of a personal computer. The components housed inside the case (such as the CPU, motherboard, memory, mass storage devices, power supply unit a ...
s, and in other locations where easy access without tools is desired.


External drives

External drives are characterized by a
female Female (Venus symbol, symbol: ♀) is the sex of an organism that produces the large non-motile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female has larger gamet ...
tool and a
male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...
fastener. An advantage of external drive fasteners is that they lack a recess in the head, which can collect water, dirt, or paint, which can interfere with later insertion of a driver tool. Also, some external drives can be engaged from the side, without requiring large inline clearance for tool access, which allows their use in tight spaces such as engines or complex pipework. Because the heads must stand out from the surface they attach to, they are rarely available in countersunk or flush designs.


Square

A ''square'' screw drive uses four-sided fastener heads which can be turned with an
adjustable wrench An adjustable spanner (UK and most other English-speaking countries) or adjustable wrench (US and Canada) is any of various styles of spanner (wrench) with a movable jaw, allowing it to be used with different sizes of fastener head (nut, bolt ...
,
open-end wrench A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as Nut (hardware), nuts and screw, bolts—or keep them from turning. In the United Kingdom, UK ...
, or 8- or 12-point sockets. Common in the 19th and early 20th centuries, when it was easier and cheaper to manufacture than most other drives, it is less common today (although still easy to find) because the external hex is now cost-competitive and allows better access for wrenching despite nearby obstructions.


Hex

A ''hex'' screw drive uses six-sided fastener heads, and the fastener is known as a '' hex head cap screw''. It can be turned with an adjustable wrench,
combination wrench A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning. In the UK, Ireland, Australia, and New Zealan ...
and 6- or 12-point sockets. The hex drive is better than square drive for locations where surrounding obstacles limit wrenching access, because smaller wrench-swing arcs can still successfully rotate the fastener. Metric sizes of the hex are specified by ISO 4032 and ISO 4033, plus ISO 4035 for Jam Nuts, and ISO 4014 and ISO 4017 for hex cap screws, ISO 4018 for Hex head screws (grade c).


Slotted Hex

A combination slotted/hex head cap is often used for self-tapping screws for metal, where the hex head enables greater torque during the initial self-tapping installation, while allowing the convenience of a slotted screwdriver to be used for removal and reinsertion.


Pentagon

A ''pentagon'' screw drive uses five-sided fastener heads, and the fastener is known as a ''penta screw'' or ''penta bolt''. It is designed to be intrinsically incompatible with many tools. Since five is an
odd number In mathematics, parity is the property of an integer of whether it is even or odd. An integer is even if it is a multiple of two, and odd if it is not.. For example, −4, 0, 82 are even because \begin -2 \cdot 2 &= -4 \\ 0 \cdot 2 &= 0 \\ 41 ...
, it cannot be turned by open-end or
adjustable wrench An adjustable spanner (UK and most other English-speaking countries) or adjustable wrench (US and Canada) is any of various styles of spanner (wrench) with a movable jaw, allowing it to be used with different sizes of fastener head (nut, bolt ...
es, which have parallel faces (and thus require a fastener with an even number of sides). Moreover, it cannot be turned by typical consumer- and professional-grade socket drivers, which possess either six or twelve points (neither of which are multiples of five). ''Penta nut'' security fasteners also are available, which can only be driven by specialized five-sided socket drivers. However, the security feature of this design can be bypassed by using some type of
pliers Pliers are a hand tool used to hold objects firmly, possibly developed from tongs used to handle hot metal in Bronze Age Europe. They are also useful for bending and physically compressing a wide range of materials. Generally, pliers consist ...
if enough force is applied. Due to the difficulty of turning these fasteners without specialized (and uncommon) five-point wrenches such as
hydrant wrench A hydrant wrench is a tool used to remove fire hydrant caps and open the valve of the hydrant. They are usually adjustable so as to fit different sized hydrant nuts. In France In France, The wrench is called "Guillemin wrench" (, pronounced ), ...
es, they are commonly used for tamper resistance by
public utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...
on
water meter Water metering is the practice of measuring water use. Water meters measure the volume of water used by residential and commercial building units that are supplied with water by a public water supply system. They are also used to determine flo ...
covers, natural gas valves, electrical cabinets, and
fire hydrant A fire hydrant, waterplug, or firecock (archaic) is a connection point by which firefighters can tap into a water supply. It is a component of active fire protection. Underground fire hydrants have been used in Europe and Asia since at least ...
s.


External Torx

An ''external Torx'' screw has a projecting head in the shape of a Torx screwdriver bit (instead of a standard recessed cavity); a Torx socket is used to drive it. The external "E" Torx nominal sizing does not correspond to the "T" size (for example, an E40 socket is too large to fit a T40, while an E8 Torx socket will fit a T40 Torx bit). These screws are most commonly encountered in the motor industry.


12-point

A ''12-point'' screw drive uses two overlapped hexagon shapes, one rotated by 30°. Standard 12-point hex socket bits and wrenches fit these screws. The screw heads are typically flanged, and may fit into standard Allen hex socket cap screw counterbores molded or machined into parts to be fastened. Compared to Allen hex sockets, the advantages of these bolts include higher torque capability and the lack of a recess to trap water. A disadvantage is the extra cost involved in forming the heads.


Tamper-resistant types

Most
tamper-resistant Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and ti ...
screw configurations rely on the common unavailability of corresponding drivers to reduce the likelihood of widespread tampering. True tamper-proof - rather than merely resistant - screw drives include the breakaway head and one-way screw drives. Both tamper-proof and tamper-resistant drives are commonly used in vandalism-prone areas, such as public restrooms; tamper-resistant in similar applications, and on equipment such as
home electronics Consumer electronics or home electronics are electronic ( analog or digital) equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment, communications and recreation. Usually ...
, to prevent easy access and thus reduce injuries and improper repairs. Recent widespread availability of assorted drive bits (including security types) minimizes this advantage, at least for some fastener types. In addition to screw drives, various nut drives have been designed to make removal difficult without specialized tools. Proprietary examples include T-Groove, Slot-Lok, Pentagon, Tork-Nut, T-Slope and Spanner designs.


Breakaway head

The ''breakaway head'' (also called ''breakoff'' or ''shear'' fastener) is a high-security fastener whose head breaks off during installation, during or immediately after the driving process, to leave only a smooth surface. It typically consists of a countersunk flat-head bolt, with a thin shank and hex head protruding from the flat head. The hex head is used to drive the bolt into the countersunk hole, then either a wrench or hammer is used to break the shank and hex head from the flat head, or it is driven until the driving head shears off. Either method leaves only a smooth bolt head exposed. This type of bolt is commonly used with prison door locks, automobile
ignition switch An ignition switch, starter switch or start switch is a switch in the control system of a motor vehicle that activates the main electrical systems for the vehicle, including "accessories" (radio, power windows, etc.). In vehicles powered by intern ...
es, and
street sign Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduce ...
s, to prevent easy removal. An alternative design leaves a low-profile button head visible after installation. In addition to breakaway bolts, breakaway nuts of similar design are available. In non-security applications, a breakaway head fastener is sometimes used as a crude
torque limiter A torque limiter is an automatic device that protects mechanical equipment, or its work, from damage by mechanical overload. A torque limiter may limit the torque by slipping (as in a friction plate slip-clutch), or uncouple the load entirely (as ...
, intended to break off at an approximate torque limit. For example, certain
toilet seat A toilet seat is a hinged unit consisting of a round or oval open seat, and usually a lid, which is bolted onto the bowl of a toilet used in a sitting position (as opposed to a squat toilet). The seat can be either for a flush toilet or a dry toi ...
fastener bolts use a breakaway plastic nut, with the driver part intended to shear at a torque high enough to prevent wobbling, while not shattering the porcelain toilet from excessive pressure. Breakaway fasteners used in a non-security application may have a second driveable surface (such as a hex head) to allow later removal or adjustment of the fastener after the initial breakaway installation. This drive type has the disadvantage of not being as precisely controlled as can be obtained by proper use of a
torque wrench A torque wrench is a tool used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. It is usually in the form of a socket wrench with an indicating scale, or an internal mechanism which will indicate (as by 'clicking', a s ...
; applications may still fail due to either too little torque being applied to correctly fasten the joint, or too much torque being required to shear the head, resulting in damage to the material being fastened.


Line Head and Line Recess

''Line Head'' and ''Line Recess'' screw drives are Japanese systems with male, female and tamper-resistant configurations. The fasteners are commonly called ''line head screws''. They are also known as ''Gamebit screws'', due to their use on some video game consoles. They are found on IBM computers, as well as
Nintendo is a Japanese Multinational corporation, multinational video game company headquartered in Kyoto, Japan. It develops video games and video game consoles. Nintendo was founded in 1889 as by craftsman Fusajiro Yamauchi and originally produce ...
and
Sega is a Japanese multinational corporation, multinational video game and entertainment company headquartered in Shinagawa, Tokyo. Its international branches, Sega of America and Sega Europe, are headquartered in Irvine, California and London, r ...
systems and their
game cartridges A ROM cartridge, usually referred to in context simply as a cartridge, cart, or card, is a replaceable part designed to be connected to a consumer electronics device such as a home computer, video game console or, to a lesser extent, electro ...
. The female sizes are designated ALR2, ALR3, ALR4, ALR5, ALR6; the male sizes are designated with an "H" instead of an "R"; and the tamper-resistant female have a "T" at the end of the designation (e.g. ALR3T). In Japan, the male sizes are often designated as DTC-20, DTC-27, DTC-40 (discontinued) and DTC-45 corresponding to a respective screw head size of 3.2mm, 4.6mm, 6.4mm and 7.7mm; with the size of the screw measured across the widest portion of the mating part of the head. The most common sizes in use for consumer electronics are DCT-20 and DTC-27.


One-way

''One-way screws'' are special screws that can be turned only in one direction. They are sometimes called ''one-way clutch screws'', but should not be confused with true "clutch" screws. They can be installed with a standard flat-blade screwdriver, but cannot be easily removed using standard tools. One-way screws are commonly used in commercial restroom fixtures and on
vehicle registration plate A vehicle registration plate, also known as a number plate (British English), license plate (American English), or licence plate ( Canadian English), is a metal or plastic plate attached to a motor vehicle or trailer for official identificati ...
s, to prevent
vandals The Vandals were a Germanic peoples, Germanic people who first inhabited what is now southern Poland. They established Vandal Kingdom, Vandal kingdoms on the Iberian Peninsula, Mediterranean islands, and North Africa in the fifth century. The ...
from tampering with them. One-way screws are practical only when the need for removal is unlikely. They are difficult to remove with conventional tools because the slot is designed to cause
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
when even minimal torque is applied in the direction to unscrew it. Instead, a one-way screw can be removed by drilling a hole through the head of the screw and inserting a
screw extractor A screw extractor held in a tap wrench A screw extractor is a tool for removing broken or seized screws. There are two types: one has a spiral flute structure, commonly called an easy out after the trademarked name ''EZ-Out''; the other has a str ...
. Alternatively, a
rotary tool Die grinders and rotary tools are handheld power tools used for grinding, sanding, honing, polishing, or machining material (typically metal, but also plastic or wood). All such tools are conceptually similar, with no bright dividing line betwe ...
with cutting disk can be used to extend the slot, the head can be gripped with
locking pliers Locking pliers (also called Vise-Grips, a vice grip, Mole wrench or mole grips) are pliers that can be locked into position, using an "over-center" cam action. Locking pliers are available with many different jaw styles, such as needle-nose pli ...
, or the screw can be removed with a pin spanner (snake-eyes driver) after drilling two holes in the slot. It can also sometimes be removed by attaching a precision drill chuck tightly to the screw head, in a manner similar to removing screws that have broken heads.


Oval

Espresso makers from
Jura Elektroapparate Jura Elektroapparate AG is a Swiss developer and distributor of home appliances, mainly espresso machines, headquartered in Niederbuchsiten, Canton of Solothurn. The company was founded in 1931 by Leo Henzirohs. Formerly, Jura ran its own facto ...
use a proprietary screw head with an eccentric oval to dissuade owners from servicing their own machines.


Polydrive

The ''polydrive'' screw drive, also known as ''RIBE'', is spline-shaped with rounded ends in the fastener head. The tool has six flat teeth at equal spacing; the sizes are determined by the diameter of the star points. Its primary advantage over older screw drives is that it resists
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
. It is used primarily in the automotive industry in high-torque applications, such as
brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...
s and
driveshaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...
s.


Proprietary head

There are specialty fastener companies that make unusual, proprietary head designs, such as Slot-Lok and Avsafe. These use special circular or oval cam-shaped heads that require complementary socket drivers. For further security, there are custom-designed fastener heads requiring matching drivers available only from the manufacturer and only supplied to registered owners, similar to keyed locks. The Ultra-Lok, and Ultra-Lok II are some of these designs that use custom keyed drivers, which tend to be confined to industrial and institutional uses that are unavailable to the average layperson. Key-Rex screws are another design, and are used in such things as ballot boxes and bank vaults. One example familiar to laypersons is for the attachment of wheels and spare tires of passenger vehicles to deter theft; one of the lug nuts on each wheel may require a specialized socket provided with the set of lug nuts. Similar security fasteners are also available for bicycle wheels and seats.


Security hex

A ''security hex'' screw drive features an extruded pin to make the fastener more tamper resistant by inserting a pin in the center of the female socket, requiring a tool with a corresponding hole to drive the fastener. This can also prevent attempts at turning the screw with a small flat-bladed screwdriver.


Security Torx

A ''security Torx'' screw drive is a common modification to socket and cruciform style drives to make the fastener more tamper resistant by inserting a pin in the center of the female socket, requiring a tool with a corresponding hole to drive the fastener. This can also prevent attempts at turning the screw with a small flat-bladed screwdriver.


Spanner

The ''spanner'' or ''Snake-Eyes'' (trademarked) screw drive uses two round holes (sometimes two slots; the same driver bits work in both types) opposite each other and is designed to prevent tampering. Other informal names include ''pig nose'', ''drilled head'' or ''twin hole''. This type is often seen in
elevator An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
s and
restrooms A public toilet, restroom, public bathroom or washroom is a room or small building with toilets (or urinals) and sinks for use by the general public. The facilities are available to customers, travelers, employees of a business, school pupils ...
in the United States, the
London Underground The London Underground (also known simply as the Underground or by its nickname the Tube) is a rapid transit system serving Greater London and some parts of the adjacent ceremonial counties of England, counties of Buckinghamshire, Essex and He ...
in the United Kingdom, some train wagons and the
Montreal Metro The Montreal Metro (french: Métro de Montréal) is a rubber-tired underground rapid transit system serving Greater Montreal, Quebec, Canada. The metro, operated by the Société de transport de Montréal (STM), was inaugurated on October 14, ...
in
Montreal Montreal ( ; officially Montréal, ) is the List of the largest municipalities in Canada by population, second-most populous city in Canada and List of towns in Quebec, most populous city in the Provinces and territories of Canada, Canadian ...
,
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
, and is seen in all
Panama Metro The Panama Metro ( es, Metro de Panamá) is a rapid transit system in Panama City, Panama. It links the south and the east of the metropolitan area to the city center. The metro was inaugurated on April 5, 2014, and it entered revenue service tw ...
wagons. The driving tool is called a "spanner driver" or "spanner screwdriver" in the US, and a "pin spanner" in the UK. They are also often used for soft spikes on golf shoes. The US military's M17 and M18 service pistols (variants of the
SIG Sauer P320 The SIG Sauer P320 is a modular semi-automatic pistol made by SIG Sauer, Inc., SIG Sauer's American branch. It is a further development of the SIG Sauer P250, utilizing a striker-fired mechanism in lieu of a double action only hammer system. Th ...
) use spanner screws to dissuade disassembly of the handgun beyond normal field maintenance except by the authorized armorer, they have also been used previously for reinforcement screws on the M14 in order to secure the front locking tab on the magazine well, and are commonly found on the recoil lug of surplus rifles. The knife and gun manufacturer Microtech uses a variation of this with 3 round holes arranged in a triangle shape. The camera company
Leica Camera Leica Camera AG () is a German company that manufactures cameras, optical lenses, photographic lenses, binoculars, Telescopic sight, rifle scopes and microscopes. The company was founded by Ernst Leitz in 1869 (Ernst Leitz Wetzlar), in Wetz ...
has used versions of this on rewind knobs and other levers on their
rangefinder camera A rangefinder camera is a camera fitted with a rangefinder, typically a split-image rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most var ...
s.


12-spline flange

The ''12-spline flange screw'' drive has twelve splines in the fastener and tool. It consists of 12 equally spaced protrusions, each with a 60° angle. It is achieved overlaying 4 equilateral triangles, each one rotated 30° over the previous one. The spline drive was part of the obsolete, U.S-designed
Optimum Metric Fastener System Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...
and was defined by
ASTM ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
B18.2.7.1M, which was withdrawn in 2011, making the spline drive obsolescent. Spline drives were specified for 5, 6.3, 8, 10, 12, 14, 16, and 20 mm size screws. Its primary advantage is its ability to resist
cam out Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Repeatedly camming out damages the screw, and possibly also ...
, so it is used in high-torque applications, such as
tamper-proof Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and ti ...
lug nut A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires. Design A lug nut is a nut fastener wi ...
s, cylinder head bolts, and other engine bolts. Care should be taken not to confuse the name of this pattern with the casual phrase "spline head" which usually refers to the XZN pattern.


Torq-set

''Torq-set'' is a
cruciform Cruciform is a term for physical manifestations resembling a common cross or Christian cross. The label can be extended to architectural shapes, biology, art, and design. Cruciform architectural plan Christian churches are commonly described ...
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 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 E-3, P-3,
F-16 The General Dynamics F-16 Fighting Falcon is a single-engine Multirole combat aircraft, multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superiority day fighter, it ...
,
Airbus Airbus SE (; ; ; ) is a European Multinational corporation, multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace manufacturer, aerospace products worldwide and manufactures aircraft througho ...
,
Embraer Embraer S.A. () is a Brazilian multinational aerospace manufacturer that produces commercial, military, executive and agricultural aircraft, and provides aeronautical services. It was founded in 1969 in São José dos Campos, São Paulo, where i ...
, and Bombardier Inc. aircraft. Phillips Screw Company owns the name and produces the fasteners. The applicable standards that govern 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.


Tri-angle

The ''TA'' is a type of screw drive that uses a triangle-shaped recess in the screw head. This drive can restrict access to the device internals but can readily be driven with hex keys. These screws are often found in children's toys from fast food restaurants, as well as vacuum cleaners, fan heaters,
elevator An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
s, camping stoves, golf clubs, Breville kettles and Master Locks, among others, Sizes include TA14, TA18, TA20, TA23 and TA27. Note that the sides of the triangle are straight, which differs from Tri-point-3 fasteners.


Tri-point

The ''TP'' (or ''Y-type'') security screw drive is similar to the Phillips screw head, but with three points rather than four. These specialized screws are usually used on electronics equipment, including some
Nintendo is a Japanese Multinational corporation, multinational video game company headquartered in Kyoto, Japan. It develops video games and video game consoles. Nintendo was founded in 1889 as by craftsman Fusajiro Yamauchi and originally produce ...
handheld hardware, Sanyo and Kyocera cellular telephones, and Fuji digital cameras.
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
uses Y-type screws to secure the battery on the 2010 and 2011 MacBook Pro, as well as an extremely small type in the
Apple Watch Apple Watch is a line of smartwatches produced by Apple Inc. It incorporates fitness tracking, health-oriented capabilities, and wireless telecommunication, and integrates with iOS and other Apple products and services. The Apple Watch was rel ...
,
iPhone 7 The iPhone 7 and iPhone 7 Plus are smartphones that were designed, developed, and marketed by Apple Inc. They are the tenth generation of the iPhone. They were announced on September 7, 2016, at the Bill Graham Civic Auditorium in San Fran ...
and
iPhone X The iPhone X (Roman numeral "X" pronounced "ten", also known as iPhone 10) is a smartphone designed, developed and marketed by Apple Inc. It is part of the 11th generation of the iPhone. Available for pre-order from October 27, 2017, it was re ...
.


Tri-point-3

''TP3'' (sometimes referred to as ''tri-lobe'' or ''tri-lobular'') uses a Reuleaux triangle-shaped recess in the screw head, to make it semi-secure because it cannot be driven by a flat-blade screwdriver and is not readily driven, as Tri-angle is, by hex keys. It is used on
fast food Fast food is a type of mass-produced food designed for commercial resale, with a strong priority placed on speed of service. It is a commercial term, limited to food sold in a restaurant or store with frozen, preheated or precooked ingredien ...
promotional toys and video games, die-cast toys, and some
Roomba Roomba is a series of autonomous robotic vacuum cleaners made by the company iRobot. Introduced in September 2002, they have a set of sensors that enable them to navigate the floor area of a home. These sensors can detect the presence of obstac ...
battery packs. There are four sizes: ''A'' = 2 mm, 2.3 mm, 2.7 mm, and 3.2 mm.


Tri-groove

''Tri-groove'' or ''T-groove'' is a design for a security screw with a flat-topped conical head and three short radial slots that do not join in the center.


Tri-wing

The ''tri-wing'', also known as ''triangular slotted'', is a screw with three slotted "wings" and a small triangular hole in the center. Unlike the "tri-point" fastener, the slots are offset, and do not intersect the center of the fastener. A version with left-hand threads is called an ''Opsit'' screw, where unscrewing can be done by turning the screwdriver clockwise, which is the opposite of tri-wing and regular screws. The design was adopted by some parts of the aerospace industry, led by Lockheed in the early 1970s on the
L-1011 The Lockheed L-1011 TriStar, also known as the L-1011 (pronounced "El-ten-eleven") and TriStar, is an American medium-to-long-range, wide-body trijet airliner built by the Lockheed Corporation. It was the third wide-body airliner to enter comme ...
, but met with mixed results due to complaints of insert damage during installation.
McDonnell Douglas McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it produ ...
also used this as a primary fastener on its commercial aircraft. British Aerospace and Airbus are also users of this fastener.


Other types

A ''U-drive screw'' has a helical thread with an angle acute enough to be driven by a hammer or pressure from an
arbor press An arbor press is a small hand-operated press. It is typically used to perform smaller jobs, such as staking, riveting, installing, configuring and removing bearings and other press fit work. Punches, inserters, or other tools/dies may be added ...
, and thus has a domed head with no means of turning it. These are most frequently driven into plastic.


See also

*
Mechanical joint A mechanical joint is a section of a machine which is used to connect one or more mechanical part to another. Mechanical joints may be temporary or permanent, most types are designed to be disassembled. Most mechanical joints are designed to allo ...
*
Wrench A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning. In the UK, Ireland, Australia, and New Zealan ...


References


Further reading

* {{Rybczynski2000


External links


Spanner Jaw Sizes


* ttp://www.instructables.com/id/When-a-Phillips-is-not-a-Phillips/ When a Phillips is not a Phillips
When a Phillips is Not a Phillips Plus So Much More!


Mechanical standards Screws Screw drives