A screw is a shaft which has a groove on its surface. It is designed to hold objects in a certain alignment. There are different types of screw heads which have different applications such as Robertson, Slotted and Polydrive.
Did You Know?
Spanner screw drives are often used for soft spikes on golf shoes.
A screw is a shaft with a coiling or spiraling groove, also called thread on its surface. Its main purpose is to join two things or objects together. It is a simple machine that transforms torque into linear force. Every screw needs to be turned in order to fit tightly with the objects joined. This turning is done with the help of a tool called screw driver. The screw driver fits into the head of the screw and turns it. Every screw has a different tool to be driven or turned. It is because each screw drive has a design that’s different from the other.
Previously, as early as the first to third century BC, screws were manufactured using wood. They were used in wine and olive oil presses. Metal screws were first used in Europe in the 15th century for cabinetry work. However, they did not become well-known until effective machine tools were produced by the end of the 18th century. The earliest screws made were only slotted. Gradually, screws with new designs started becoming popular when several advances in screw making began taking place. This was due to the various needs in industry and the fact that persistent innovation is a driving economic force. There are various drive types of metal screws used in various applications. They are described as under.
Types Of Screw Drives
This is the most widely used and popular type of screw head. It is the oldest screw head produced. It has a slot in the head, which holds the flat-bladed screw driver. It can have a round or a flat head. It is used in woodworking applications. However, the use of screwdrivers with the slotted drives are declining because the driver tends to slip out when subjected to heavy pressure, thereby damaging the screw head, the screw driver, and the surrounding area. So, it is not used for mechanical purposes.
The screwhead, Phillips has been named after its creator, Henry F. Phillips. It has a cross-shaped recess on the head, i.e. two slots at 90 degrees to each other. The force that is required to turn the screw is less which is why it better than the slotted screw drive. Like the slotted drive, this screw head too causes the screw driver to cam out when high torque is applied to tool. However, the intensity is lesser compared to that of the slotted drive. Hence, the damage is limited to the screwdriver instead of the work or the screw head. The purpose of its design was to make the driver cam out so that it did not result in over-tightening. It has applications in home and workshops.
This square screw drive has been named after the Canadian inventor, P. L. Robertson. It a square-shaped recess in the screw head, which holds the tool firmly. It is also called a Robertson drive. They are highly resistant to camming out which is why they are being used more. The driver does not slip off the head easily even when high force is applied to it. They are used by woodworkers, electricians and motor mechanics.
This screw head has a six-pointed star-shaped pattern. It is popularly known as star. It can resist cam out much better than Phillips head or slot head screws. Torx screw finds applications in automobile industry, telecommunications, appliance industries and others. A version called Security Torx or tamper-resistant TORX screws has a small post in the middle of the drive that prevents a TORX driver from being inserted. A more advanced type, TORX Plus was introduced later. It allows for greater contact area between the driver and the screw head and hence higher force can be applied to it. It also helps reduce damage. Another variant, a tamper-resistant version of Torx Plus, has five lobes with a solid post in the center. It finds uses in correctional facilities, high security applications, electronic devices and others.
These screw drives are a combination of two drives. They were made with the intention that different kinds to drivers could fit into it and turn it. They are also called combo or combi heads. For example, a slotted and Phillips head can form a combination drive. It is used in attaching knobs to furniture drawer fronts. The other kinds of combinations drives are a Phillips and Robertson known as quadrex, a Robertson and a slotted, a torx and a slotted, and a triple-drive screw that can take a slotted, Phillips or a Robertson. These screw drives increase productivity by transmission of more torque and reduces the possibility of cam-out.
This screw drive has a triangular slot on the screw head. They are used in children’s toys, vacuum cleaners, fan heaters, elevators and camping stoves.
The posidriv is an advanced form of the Philips drive. Its appearance is similar to the Phillips, but is a little different. It has two crosses. One cross is broader than the other cross. The narrower cross is set at an angle of 45 degrees from the cross recess. It allows for a better resistance to cam out than the Philips drive and thus can sustain more force.
This screw head is often mistaken with the Pozidriv, but they are not that similar. The screwhead is identical to the Pozidriv, but has two identification ticks. Supadriv lets a small angular offset between the screw and the driver, but Pozidriv has to be directly in line. However, one screwdriver can be used to turn the pozidriv and the supadriv. Supadriv is a better screw drive than the posidriv due to its superior bite screw. It is efficient and causes minimal cam-out.
It is a screw head with ridged or knurled sides. It has an over-sized head that allow the screw to be gripped easily and hence tightened or loosened by hand. This type of screw drive is used in places where removal and re-installation are needed. They are also used in electronic devices.
This screw head has three slots in the form of wings and a triangular hole in the center. It is used in the aerospace industry and household appliances.
This screw drive has a spline-shaped slot in the head. It has six teeth with flat tips at equal distances. It ensures compactness and allows for great torque transmission when driving. It is used primarily in the automotive industry.
This screw drive is a combination of two squares set at 45 degrees. It can allow for a better grip by the screw driver while turning it.
Triple square screw drives have twelve tips separated at equal distances. The recess is made of three squares and each of them is set at right angles. They are also called XZN. They are used in German, European and Asian vehicles.
These screws have slots which are narrow at the center and gets wider as they proceed towards the edges. They can be turned only in one direction. The shape of the slot allows a flat-bladed screw driver to rotate the head in the driving direction, but not in the removing direction. They can have either a flat head or a round head. They are used in restroom fixtures and on vehicle registration plates. They are mostly used in thin metal or wood.
The spanner screw has two rectangular pins or holes in its head. It is also called snake eyes. This design prevents over-tightening of the screw while turning it. It does not allow for transmission of high torque. It is used in electronics, restroom stall doors, and elevators.
This screw drive was named after English inventor, Frearson. It is occasionally called by its former name of Reed & Prince (owing to its producer, Reed & Prince Manufacturing Company). This screw drive is similar to a Phillips. However, the V-shaped angle that the slot forms is more pointed than Phillips. It allows for greater torque with minimal cam-out. Moreover, one Frearson screwdriver can fit well in all Frearson screw sizes. It is compact and economical. It is used in marine hardware.
The Mortorq Spiral System is an efficient drive in terms of cost and operation. It has a deep slot, which allows full contact of the driver over the slot, thus creating high torque. There is no possibility of damage to the driver or surrounding area. Its head is made with light-weight material. It is used in automotive and aerospace applications.
This type of screw drive has a hexagonal slot. The slot has six sides which are at a 120° angle to each other. It can be driven by a six-sided driver. It is better than the square drive in situations where surrounding obstacles limit the turning of the driver.
The TTAP® screw drive is an improved hexalobular/Torx drive. It is designed to work with all types of assembling. It is possible to work it with a single hand due to its stick-fit-no-wobbling feature. The user does not have to place one hand on the screw and the other on screwdriver.
The spline screw drive has a head consisting of twelve splines. It offers great resistance to cam-out. It is used in high-torque applications, like tamper-proof lug nuts, cylinder head bolts, and other engine bolts.
It is a cruciform screw drive with a cross having four arms, which do not form an intersecting slot, as the opposite arms are not in the same line. It allows for great torque transfer. It finds applications in the aerospace market.
The TP3 screw drive has a head with a triangular slot with rounded sides. It is a rare type of screw drive. It is used on Nintendo, Game boy, promotional toys and video games.
This drive system has six splines. It is more advantageous over other screw drives, as other drives tend to expand the socket rather than tighten the screw drive. The design of this screw addresses problems like cam-out, socket expansion and rounding of screwdrivers. They are used in avionics, high-end communications equipment, cameras, air brakes, construction, farming and military equipment and astronomy.
Clutch screw drives are of two types; Type A and Type G. Type A looks like a bow tie and is used in trailer trucks, and electric motors. Type G looks like a butterfly and finds applications in maintenance applications that need removal at short intervals. They are used in the manufacture of mobile homes and recreational vehicles.
A square head screw drive has a square head on the fastener. It was popular in the 19th and early 20th centuries, but is rarely used now.
A pentagon screw drive has a five-sided head. It is used in water meter covers, natural gas valves, and electrical cabinets.
This is a screw drive with a hexagonal head. It is commonly seen on bolt products and also on many screw products. It can come in several versions. It can transmit higher tightening torque than other head styles.
Various Shapes of Screw Heads
This screw head has a countersunk head with a flat top. It is recommended for use in things to distribute pressure over a larger and less angular surface. It is most commonly used on door hinges or into steel applications. They can be also seen on bolt products, aluminum, and plastics.
This is a scew head with a tall domed head. It has a head whose diameter is less than the pan head. It is usually used as wood screws and machine screws.
This screw drive has a slightly rounded head with short vertical sides. It is mostly substituted in applications requiring round, truss or binding heads.
Oval Head/Raised Countersunk
This screw drive has a countersunk head similar to the flat head, but with an oval-shaped top. It is used when a more decorative finish is required. It is generally chrome or nickel-plated.
Fillister Head/Raised Cheese
This type of screw head has a diameter lesser than the round head, but is raised up and has a shallower recess. The smaller diameter head increases the pressure applied on the area and can be set close to flanges and raised surfaces. It is rarely used today though it may be used with counterbored holes. Earlier it was used as machine screws.
This screw drive has a hex head with a built in washer to protect assembly finish. It can also transmit higher tightening torque levels than other head styles. It is very versatile and used in metals, woods, plastics and others.
Truss Head/Oven Head/Stove Head/Oval Binding Head
This screw head has a rounded top with an extra wide bearing surface, more than a round head. It is designed to prevent tampering and to cover larger diameter holes in metal surface.
This head fairly matches with a round head, but is flatter. It has been designed for light fastening applications. It is mostly seen on self-drilling and machine screws.
This screw head has a disc with cylindrical outer edge. Its height is about half the diameter of the head. It is mostly found on machine screws.
This screw head is of a square shape. It is not much in use now. Earlier, they were used on timber bridges.