Panel Screws

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Screw Type

Captive screws lock in place, either with locking heads, clips that hold the screw in place, or a female sleeve that attaches the screw to a work piece. They are commonly used in the aerospace and computer industries, as well as other rapid assembly applications, and in environments where it would be dangerous for a screw to fall and clog machinery.

Concrete screws are designed with hardened threads that are not too brittle and can screw into concrete, brick and other hard materials.

Machine screws are driven into tapped or pre-drilled holes. Often used with nuts, machine screws are primarily available in smaller sizes and have blunt ends. They are often used to fasten metal parts together. Machine screws come in a wide variety of head and drive styles, but they are most commonly used with slotted or Phillips drivers.

Panel screws are designed to remain firmly fixed. They often mount flush with the object on which they’re used. To hold them captive use a retaining washer (sold separately). They have blunt ends and are used with computer parts, panel assemblies, cabinets, and other items produced on assembly lines.

Self-tapping screws have sharp threads that create their own hole when they are driven. They have sharp, pointed tips and are self-starting in soft metal, but require a pre-drilled hole with harder material.

Set screws generally do not have external heads. They can have blunt or pointed ends and are used for holding pulleys, gears, and other parts from turning relative to a shaft and to prevent loosening due to vibration.

Shoulder screws, also known as shoulder bolts, have threading only part way up the screw and then a smooth shaft close to the head to act as a spacer or bearing. The shaft is generally longer than the thread of the screw, and the point is blunt. Shoulder screws with round shafts are commonly used for items that require rotation, while those with square shafts are used to lock into place and prevent rotation. They are often used in mechanical or automotive applications. The length indicated for a shoulder screw denotes the length of the shoulder not including the head height or threaded length.

Socket cap screws, also known as Allen head screws, have a recessed drive, and are commonly used when there is not enough clearance for a conventional wrench or socket. They are fastened with an Allen wrench, which is also called a hex wrench or hex key.

Thumb screws are designed to be twisted into a pre-drilled and tapped hole by hand. They have blunt ends and are often used on electronics and computers.

Wood screws have coarse threads that are designed to help them bite into wood and resist pull-out. They have sharp, pointed tips that are designed for use in wood.

Fasteners
- Screws
  - Panel Screws

Captive Screws
Concrete Screws Machine Screws Panel Screws
Self Tapping Screws Set Screws Shoulder Screws Socket Cap Screws
Thumb Screws Wood Screws

Screw Head Style

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Screw Head Style

Binding head screws are similar to those with pan heads; they are considered an older style and are commonly replaced by pan screws. Binding heads have a deeper slot and are slightly undercut under the head. They are often used for electrical work.

Binding undercut head screws are similar to pan heads, but they have a deeper drive slot, which spans the head diameter. The underside of the head is recessed. They are commonly used for electrical work.

Bugle screws have a curved, inverted cone-shaped head, and a flat head surface with slightly rounded edges.

Button head screws are similar to standard pan head screws but have a curved top.

Cheese head screws have a thick cylindrical head with a deep slot for increased driving power.

Fillister head screws have a thick cylindrical head with a deep drive slot for higher levels of torque. The head is smaller than a round head.

Flange hex head screws screws have an extra bearing surface between the top of the screw head and the body that provides an additional gripping strength. This flange area resembles a flat washer, with its semi-flat disc shape.

Flat head screws are designed to fit flush to the surface when used with countersunk holes.

Flat fillister screws are similar to fillister, but with a reduced head height.

Flat undercut screws have a countersunk, flat head with a cone-shaped bearing surface, and are undercut to a lower head height, allowing for a shallower countersink.

Hex head screws are hexagonal shaped with a flat bearing surface.

Knurled head screws have ridges or grooves on the head, which are designed to be twisted into a tapped hole by hand, without using tools.

Low head socket cap screws have a head that is about half the size of a standard socket head. They are not recommended for high strength applications.

Modified truss screws have an extra-wide, low profile dome, allowing for a wider load distribution. They have a slightly rounded top and rounded side edge.

Oval head screws are tapered on the bottom like flat heads to fit flush in countersunk holes, but they have an oval top.

Oval undercut screws have a slightly domed, arched head that has an oval-shaped curve from the side view, and a round shape from the top view. The head is undercut to a lower head height, allowing for more thread length. The base of the head is beveled towards the body.

Pan head screws have a low, large cylindrical head with a high rounded top edge. This head type is often recommended to replace older head styles such as round, binding, or truss.

Round head screws have a dome shape. They are considered an older style and are commonly replaced by pan screws.

Socket cap screws, also known as Allen head screws, have a recessed drive, and are commonly used when there is not enough clearance for a conventional wrench or socket. They are fastened with an Allen wrench, which is also called a hex wrench or hex key.

Spade head screws (with shoulder) have an easy-to-grasp spade-shaped head, which allows for easy tightening and loosening by hand. The shoulder acts as a bearing surface.

Spade head screws (without shoulder) have an easy-to-grasp spade shaped head, which allows for easy tightening and loosening by hand.

Square head screws have a square shaped, prominent head that is easy to access with a wrench or by hand, when more torque is needed.

Truss head screws have an extra-wide lower-profile dome with a slightly rounded top.

Screw Drive Style

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Screw Drive Style

Bristol drives have four or six splines, which are sharp plateau-like ridges on the fastener and on the tool. Most of the turning force is applied at right angles to the fastener's spline faces, which reduces stripping the fastener head. These drives are often found in softer metals, such as brass.

Clutch drives lock into the fastener head when the tool is turned counterclockwise, and unlock when the turning direction is reversed. Type A, sometimes called a standard clutch, is an older style. Newer type G drives are recommended for maintenance work, and other applications where the fastener must be removed and reset frequently.

Combination Phillips-slotted drives are used with either a Phillips or standard slotted driver. The drive style is designed so that the driver will cam out, or slip out, under pressure to prevent over-tightening. These screws are often used to attach knobs to furniture.

Cross drives are used with either a Phillips or standard slotted driver. The drive style is designed so that the driver will cam out, or slip out, under pressure to prevent over-tightening. These screws are often used to attach knobs to furniture.

Double hex drives have a 12-point socket shaped like two hexes, which are rotated and overlaid upon each other. Although double hex drives resemble triple square and spline drives, they are incompatible. Standard hex keys may be used with double hex sockets, but the near-circular shape decreases torque and increases stripping the fastener head.

External hex drives are six-sided, or hexagonal, and are driven by a crescent wrench, combination wrench, or sockets. They require minimal clearance above the fastener because they can be tightened or loosened from the side. External hex drives outperform external square drives in scenarios with limited fastener access, because smaller swing arcs may be used to rotate the fastener.

External square drives are four-sided, or square-shaped. They are driven by a crescent wrench, open-ended wrench, or sockets. They require minimal clearance above the fastener because they can be tightened or loosened from the side. External square drives are less common than external hex drives. Square fasteners are often found in plumbing, lighting equipment, and gate hardware.

Frearson drives, also known as Reed and Prince drives, have a cross-shaped slot like a Phillips drive. Unlike a Phillips drive, Frearson drives are a perfect cross shape, for greater torque and more cam out resistance. These drives also have a more pointed 75 degree internal V shape. One driver or bit fits all fastener sizes, an advantage over Phillips drives. Unfortunately, it is easy to confuse Frearson and Phillips drives, increasing the chance that the incorrect tool will be chosen, and increasing the chance of damage to the workpiece, fastener, or tool. These drives are often used in marine hardware.

Internal hex drives, also known as hex-socket drives, are similar to hex drives, but have a hexagonal hole in the center that requires an Allen key, also known as a hex key or Allen wrench.

Internal square drives, also known as Robertson drives, have a square-shaped center. They require a special driver and are designed to maximize torque. The driver will not cam out, so the fastener does not have to be held in place during installation, leaving both hands free to drive the internal square fastener. These drives are commonly used in woodworking and carpentry.

JIS drives, or Japanese Industrial System drives, are commonly found in Japanese electronics. They resemble the Phillips drive but are designed to not cam out, and may be damaged by a Phillips driver. Often, a single dot or an X mark near the cross-shaped slot identifies a JIS drive over a Frearson or Phillips drive.

Lobed drives have an external six-sided star shape, which allows a more even spread of force on the fastener head, thereby helping to prevent tool or fastener damage. Torque transfer on a lobed fastener is greater than for the corresponding internal star. Lobed fasteners weigh approximately 20% to 40% less than equivalent hex and pan head fasteners, which is advantageous for applications where weight may be a concern, such as automobile engines.

Not applicable defines a fastener that is either hand-driven, or held in place during use. Hand driven examples include knurled screws and spade screws. Since these are head styles, the drive style is not applicable. Carriage bolts, eye bolts, J bolts, and U bolts are all held in place during use while the nut is fed onto the threaded end of the fastener, tightening the bolt in place from the end rather than the head. The carriage bolt is held by its square neck, while eye, J, and U bolts are held in place by hand or with a tool.

Pentagon drives have five-sided fastener heads. The fastener is sometimes known as a penta head bolt or screw. Pentagon drives require a specific tool with a five-point socket. Utilities such as water meter covers, natural gas valves, fire hydrants, and electrical cabinets are commonly secured with penta fasteners. The non-standard shape offers a higher degree of security over a hex fastener, since tools that are commonly used with hexes, such as crescent wrenches, are not compatible with pentagon driven fasteners.

Phillips drives have x-shaped slots with rounded corners and are driven with a Phillips screwdriver. The slot is designed so that the driver will cam-out, or slip out, under pressure to prevent over-tightening.

Phillips-square drives, also known as Quadrex, are a combination of the Phillips and internal square screw drives. These drives are less prone to cam out than either Phillips or square drives, allowing higher torque to be used. While a Phillips or a square tool may be used, a dedicated tool is available for this drive system that increases the surface area between the tool and the fastener so that additional torque can be applied.

Pozidriv drives are an improved version of the Phillips drive, with less likelihood to cam out, allowing greater torque to be applied. Pozidriv screwdrivers and screws can be distinguished from Phillips by the thin markings at 45 degrees from the cross. Pozidriv drives are visually very similar to Phillips, even with the distinguishing marks or ticks, so the drive styles may easily be confused. A Phillips driver will turn a Pozidriv fastener, though damage to the fastener may result. However, a Pozidriv driver will not turn a Phillips fastener. Pozidriv drives are sometimes confused with Supadriv drives, which are similar in appearance but a later development by the same company.

Slotted drives have a linear slot and are used with a flat-bladed screwdriver. These drives are commonly used in woodworking and are prone to slippage.

Spline drives have twelve splines, or rounded plateau-like ridges, on the fastener and tool. Spline drives resist cam out, so they are frequently used in high-torque applications, such as tamper-proof lug nuts.

Star drives, also called Torx drives, have 6-pointed indentations that provide more driving surface area. These screws resist cam-out better than Phillips drives or slotted drives. They are used with a Torx screwdriver.

Supadriv drives are very similar in function and appearance to Pozidriv, and the two are often confused. Because the Supadriv drive is a later development by the same company, the same screwdriver heads may be used for both types without damage. The Supadriv drive allows for a small angular offset between the tool and fastener, while the Pozidriv drive must be directly in line. The Supadriv drive has two identification marks, or ticks, to the Pozidriv's four. When driving into a vertical surface, Supadriv outperforms Pozidriv by reducing cam out.

Tamper-resistant drilled spanner drives have two holes opposite each other and are sometimes called snake eyes screws. Screws with tamper-resistant drives require special tools for removal and are used to discourage theft and vandalism.

Tamper-resistant one way drives have sloped slots, so the screw can be driven in but the driver slips out if you try to loosen the screw. Screws with tamper-resistant drives require special tools for removal and are used to discourage theft and vandalism.

Tamper-resistant pin-in-head hex drives have a hexagonal shaped drive with a pin in the center. Screws with tamper-resistant drives require special tools for removal and are used to discourage theft and vandalism.

Tamper-resistant pin-in-star drives have a star-shaped hole with a pin in the center and cannot be removed with a standard torx screwdriver. Screws with tamper-resistant drives require special tools for removal and are used to discourage theft and vandalism.

Tamper-resistant tri-groove drives have slots in the outer edge of the head which provide driving force with a lowered risk of fastener damage and failure. Machine tools can be used with this driver socket, making this drive suitable for use where security and fast assembly are required, such as in the mass production of electronics.

Torq-set drives are used in high-torque applications where breakage is a concern, such as aerospace manufacturing. The Torq-set head is similar in appearance to a Phillips drive, as both have a cross-shaped slot with four arms, although the Torq-set cross arms are offset from each other. Because of this, neither a Phillips nor a flathead tool will fit a Torq-set fastener.

Tri-wing drives, also known as triangular slotted drives, drives have three radial slots extending from the center of the fastener head, positioned at 120 degrees to each other. Tri-wing fasteners may or may not include a small triangular hole in the center of the three wings. The same driver may be used for both types. These fasteners are most commonly found on electronics equipment, such as game consoles.

Triple square drives, also known as XZN, drives have 12 equally spaced tips, each with an internal 90 degree angle. Three identical overlaid squares are rotated to form a pattern. Triple square drives are useful in higher torque applications, such as drive train components. Many German vehicle manufacturers use triple square fasteners on their automobiles.

Uni-drive drives have a series of stacked pentagons, as a socket in the fastener and as a pyramid-like shape for the driver, that are intended to reduce delay by using one driver for all fasteners. The driver fits 1/2" to 1" (M12 to M24) fasteners, lowering the overall need to change bits. Uni-drive drives offer additional torque and less cam out when compared to a Philips head fastener, due to the additional points of contact between driver and fastener.