Types of screwdrivers and slots: description and application

Straight slots

Straight (flat) slot (SL)

A straight flat slot is the simplest and cheapest type of slot in production, in the form of a straight slot for a flat screwdriver. It has been used for centuries to this day, in tasks that do not require a high tightening torque or high labor productivity. It is also used in the restoration of old furniture, vehicles and equipment. A straight flat slot is inconvenient for use with a power tool, since the tool tends to slip out of the slot with scratching of the surrounding surface, and does not provide centering. Due to these disadvantages, it is displaced by other types of slots.

Screwdrivers for a flat slot can have different types of sharpening: both classic - two flat faces at a small angle, and radius (hollow-ground). Radius sharpening is preferable, since it is less prone to pushing out the tool and less often leads to a breakdown of the slot, but such screwdrivers are inconvenient for use for other purposes (to pry, split, bend, etc.).

In Russia, the straight slot is standardized in GOST 24669-81.

Coin slot

Coin slot with a concave bottom surface, it is used where the availability of the tool is not assumed. A coin or other flat object is suitable for rotating such a slot. Often, such a slot has covers of battery compartments of household appliances, for example, bicycle computers.

Hi-Torque

The Hi-Torque slot was developed by Alcoa Fastening Systems, for tasks in which high torque is required, as well as the possibility of frequent twisting - unscrewing fasteners. It has a radial recess of the slot, unlike a flat one in a simple flat slot.

Cross

A combination of two flat slots at right angles. Provides a kind of duplication, if for some reason one flat slot is damaged, then you can use the second one.

Cross-shaped slots

The slots listed below are called "cruciform", since their shape is based on a cross, they can also be called "cross" or "plus". A double straight slot in the form of a cross is not included in this group, since it is a combination of two straight slots, and not an independent form. Some of the above types of cross slots are described in the ISO 4757 standard Cross recesses for screws.

Friason

Slot type Frearson, also known as Reed and Prince described by the ANSI Type II Cross Recess standard, it is very similar to the Phillips slot, but has sharp edges and a larger angle of the screwdriver tip. One of the advantages over the Phillips slot is that one screwdriver fits all screw sizes. Fasteners with this type of slot can be found in foreign marine equipment, and a "Friason" type screwdriver is required for correct operation. Clear sharp edges allow you to transmit a large torque, unlike a Phillips-type slot, which is prone to pushing the tool out of the slot at high torques. It was developed by an English inventor named Friason in the 19th century and products with such a slot were produced from the late 1930s to the mid-1970s. The Reed & Prince Mfg Company. The Company of Worcester, Massachusetts, filed for bankruptcy in 1987 and was liquidated in 1990. Another company Reed & Prince Manufacturing Corporation, now of Leominster, Massachusetts acquired part of the assets, including the name in the liquidation of the company.

Phillips

Phillips cross slot according to GOST 10753-86 type H, as well as Type I Cross Recess in the ANSI standard. The only cruciform slot widely used in the USSR, as a result, almost all Soviet-made phillips screwdrivers have this slot.

This type of slot was developed by John P. Thompson, who, after unsuccessful attempts to interest manufacturers, sold the patent to businessman Henry Phillips. Phillips founded the Phillips Screw Company, improved the design of the slot and promoted his product on the market. The original patent expired in 1966, but Phillips Screw Company continued to improve the design of the slot.

American Screw Company was engaged in developments that increase the efficiency of screw production, and successfully patented their improvements. Other fastener manufacturers rejected these developments, since the complex shape of the slot deepening significantly complicated the production process, compared with simple milling of a flat slot. At the same time, the design of the slot proposed by the company was the solution to a number of problems of a straight flat slot - the tendency to push out the tool, the need for precise alignment in order to avoid disruption of the slot, and the inconvenience of working with electric and pneumatic tools.

The tool for slots of the Phillips type is marked with the letters "PH", and the size number 0000, 000, 00, 0, 1, 2, 3, or 4 (in order of increasing size); number it does not transmit any specific geometric size and is conditional. 

The slot of the "Phillips" type differs significantly from the externally similar slot of the "PoziDriv" type.

The design of this slot is often criticized for pushing out the tool when tightening, as a result of which this slot provides a smaller tightening torque than other cross-shaped slots. For a long time there was a popular opinion that this was done on purpose, allegedly it allowed to assemble aluminum planes without unnecessarily strong tightening. No evidence of this hypothesis has been found, in addition, this "advantage" does not appear in the description of the original patent. However, the 1949 additions to US Patent #2,474,994 describe this feature.

Posidriv

Slot Pozidriv — an improved version of the phillips slot. Described as "Type IA" by the ANSI standard. In Russia , GOST 10753-86 type Z is described .

The slot was patented by GKN Screws and Fasteners in 1962. The slot design is specifically designed to transmit more torque than a phillips-type slot, and is less prone to pushing the tool out of the slot. It is very similar and compatible with a Supadriv type slot.

Screwdrivers for the slot type "Pozidriv" are often marked with the letters "PZ" and a number symbolizing the size: 0, 1, 2, 3, 4 or 5 (in ascending order of size). The numbers denote a conditional size and do not convey any precise geometric parameter.

The slot "Pozidriv" has additional ribs on the screwdriver and a cross on the head of the slot for visual difference from the slots of the "Phillips" type. Additional ribs and risks are rotated 45° from the main cross of the slot.

If the faces on the Phillips screwdriver have a small radius (which leads to the tool being pushed out of the slot at high torque), then the Pozidrive screwdriver has parallel faces. The presence of additional drawings for identification complicates the manufacturing process.

Slots like Philips and posidriv, despite the apparent identity, are not interchangeable. The philips bit cannot fit tightly into the posidriv slot, and the posidriv bit damages the philips type slot with its sharp flat edges. In this case, the contact between the slot and the tool is not complete (point) and when applying force, both the bit and the slot of the tool will be damaged and worn out.

Supadriv

Slot type Supadriv is very similar in appearance and functionally to the posidriv type slot, and is a subsequent development of the posidriv from the same company. The description of the posidriva is also relevant for the supadriva. Although each slot has its own screwdriver, one type of screwdriver can be used for both supadriv slots and posidriv slots, without harm and consequences in most cases. Supadriv and posidriv are slightly different in details, the supadriv that appeared later allows for some axial displacement of the screwdriver, while the posidriv should be strictly aligned.

Phillips II

Phillips II slot compatible with regular phillips screwdrivers, but has vertical ribs inside the cruciform recess, which engage with the corrugation on the screwdriver, thereby reducing the ejection effect of the slot. The corrugation on the screwdriver has the trademark "ACR" (Anti Cam-out Ribs).

French slot

French slot, also known as BNAE NFL22-070 by the standard number in the Bureau de normalisation de l'aéronautique et de l'espace. It has a cross-shaped slot of a stepped shape, small in the center and larger closer to the edge.

JIS B 1012

Japanese slot standard JIS B 1012 is widely used in Japanese equipment. It looks similar to the Phillips slot, but it is designed to minimize the effect of pushing the tool out of the slot, and therefore it is damaged by the tool under the Phillips slot. The head is usually marked with a dot on one side of the cross.

A specific "JIS" standard phillips screwdriver for use with these slots is available and available on the market.

Mortorq

Slot Mortorq was developed by Phillips Screw Company, for use in the automotive and aviation industries. The design of the fastener with such a slot has a low weight, a small profile and a large transmitted torque, allowing to reduce the risk of a slot failure.

Design changes

Many screwdrivers have one or more of the following design changes.

Ratchet mechanism (reversible screwdriver)

A more complex version of a screwdriver is a screwdriver with a ratchet mechanism ("ratchet"), thanks to which the rod with the tip freely scrolls in the handle in one direction. This design allows you to work with a screwdriver with one hand (and any one) without intercepting the handle. Depending on the functions performed (unscrewing or screwing), it is necessary to change the direction of scrolling of the rod. The ratchet mechanism is equipped with a switch for this purpose, made in the form of a lever, a slider switch or a clutch. The middle position of the switch blocks the rotation of the rod in the handle.

Screwdrivers-inserts (replaceable tips, nozzles)

Universal screwdrivers are also available, which are a handle to which it is possible to attach a whole set of tips or replaceable heads for different types and sizes of slots. Fastening is carried out using a magnetic or spring holder (screwdrivers-inserts with a drive external hexagon, for example, according to GOST 30092-93, or replaceable inserts for a universal screwdriver with a cam leash according to OST 1 52461-01 and so on), collet clamp or other method. Screwdrivers-inserts can have different lengths.

The colloquial name of the screwdriver-insert— "bit"— is not found in the official regulatory technical documentation.

Отвёртки-вставки являются оснасткой (расходным материалом) для шуруповёртов и винтовёртов.

Dielectric screwdriver

For operation near conductors under electric voltage or with live parts, the screwdriver can be covered with insulating material. Usually the entire handle and the rod are covered with the exception of the tip. The dielectric coating of such a screwdriver is calculated for guaranteed protection against voltage up to 1000V, when it is released from production, it is tested and a mark is placed on the handle.

Indicator screwdriver

Indicator screwdriver (screwdriver probe, screwdriver tester)- portable single—function electrical measuring device (phase meter), manufactured in accordance with GOST 30012.1-2002 Analog devices showing direct-acting electrical measuring devices and auxiliary parts to them. It is used to detect a phase wire (to assess the presence of a voltage phase on a given current-carrying section) during electrical installation work. The indicator screwdriver has a dielectric coating. Due to the design features, as a rule, this type of screwdriver is not designed to apply significant mechanical forces.

Operating principle

In accordance with the laws of physics, one of the wires of the household lighting network is neutral and under normal conditions does not pose a danger to humans. To avoid an accident, as well as to determine the location of the phase wire, an electrician must determine it. To do this, professionals use an incandescent lamp as a probe or use an indicator screwdriver that works in accordance with the principle that was discovered in the XIX century by Heinrich Hertz. The principle is based on electromagnetic interaction. In the household electrical network, alternating current is most often used, with a frequency of 50 Hz, the electromagnetic waves generated in this case are actively radiated into the surrounding space. Thus, if you touch the test wire with a metal wedge-shaped working surface, the measuring screwdriver becomes an antenna for receiving waves of frequency 50 Hz. At the same time, the gas-discharge indicator lamp, which, unlike an incandescent lamp, has a break in the electrical circuit between the electrodes, begins to work on the principle of an electric capacitor, between the plates of which, under the action of alternating voltage, a current is induced, which causes ionization (spark gap) and the glow of the gas filling the bulb of the lamp. Initially, the radiation resistance is high and the electron flux is not enough for sufficient ionization of the gas gap between the electrodes in the lamp. However, it is enough to touch the contact button with your finger, the electrons rush to the body and the resulting current is the cause of gorenje indicator lamp screwdriver. This effect of the lamp glow when touching the working surface of the indicator screwdriver to the phase wire is observed regularly, regardless of whether there is contact of the master's body with grounding or not. As a result of contact, part of the energy is extinguished by the skin, causing barely noticeable heating of the contact areas, but a significant part is radiated into the surrounding space. The surface area of an adult's body exceeds one square meter, because the power dissipation into the ether is significant. This phenomenon causes an increase in the number of electrons passing through the discharge lamp, and it lights up. So, the initial ignition of the spark gap occurs due to a potential difference: a wired network for transmitting and distributing current has a certain potential, the difference of which with the human body is enough to ignite the arc. In the XX century, LEDs became widely available, which found application in modern indicator screwdrivers, replacing gas-discharge lamps. The use of LEDs in general does not change the principle of operation of the indicator screwdriver, however, it eliminates the need to take up the contact button with your hand, since energy is already radiated through the metal contact pad. However, if you do touch it, the size of the receiving antenna increases, which helps to increase the brightness of the LED.

As a protection against a possible electric shock, a resistance of a high nominal value was consistently installed in the circuit of the indicator gas-discharge lamp before entering the contact plate. The purpose of the resistance is obvious: if an unlucky electrician touches a phase wire with his bare hand (through a spark gap) during operation, and leans against a grounded conductive object with the other part of the body, then taking into account the relatively small resistance of the human body to alternating current, there were no fatal consequences.

Heel for striking

Some screwdrivers have a rod that runs through the entire length of the handle and expands at the end opposite the tip. This extension (heel) can be struck with a hammer without the threat of destruction of the handle. Such measures are resorted to in cases when the slot of the part is heavily soiled and otherwise it is not possible to reliably hook the part, as well as in some other cases. In some screwdrivers, the heel for striking is made in the form of a hexagonal turn-key leash.

Adjusting screwdriver

A screwdriver made entirely of plastic or ceramic. It is designed for tuning sensitive equipment, reduces hand-pointing, does not distort the parameters of the tuned circuit (capacitance, inductance or magnetization).

Impact screwdriver

Impact screwdriver for replaceable heads (mentioned in GOST 29308-92. Mounting tool for screws and nuts. Nomenclature)- a mechanical device that converts the impact energy into torque. As a rule, the impact screwdriver (impact-rotary screwdriver) is equipped with a reverse that allows you to change the direction of rotation.

Watch screwdriver

The watch screwdriver is a watch tool (watch repair tool) designed for for carrying out precise work with a reduced in size, particularly precise working part and a rotating head on the handle for convenience in working with small-sized hardware heads. Sometimes the design provides a device for installing replaceable nozzles with different sizes of the working part, specially sharpened to accurately match the screw heads of small and especially small sizes. This type of screwdriver is used for assembling— disassembling not only watches, but also microcalculators, cameras, players and other electronics.

Electric screwdriver

The development of the idea of a screwdriver is a specialized electric or pneumatic tool that drives a replaceable tip (electric screwdriver, screwdriver, screw). Drills are also used for this purpose, but the use of a drill that does not have a torque regulator coupling is fraught with damage to the fastener or screwdriver insert.

GOST and other standards

• GOST 29308-92. Mounting tool for screws and nuts. Nomenclature
• GOST 21010-75 Dielectric screwdrivers. Technical conditions
• GOST R 53935-2010 Screwdrivers for screws and screws with a cruciform slot. General technical requirements, control and testing methods
• GOST R 52785-2007 Locksmith screwdrivers for screws and screws with a cross-shaped slot. The working part. Dimensions
• GOST 24437-80 Screwdrivers for locksmith and assembly. Blades of locksmith and assembly screwdrivers for screws and screws with a straight slot. Dimensions
• GOST 30092-93 Screwdrivers-inserts with a drive external hexagon for screws with a straight slot. Dimensions
• GOST 17199-88 Locksmith and assembly screwdrivers. Technical conditions (Action completed 01.01.2012)
• GOST 10753-86 Cross-shaped slots for screws and screws. Dimensions and control methods
• GOST 10754-80 Screwdrivers for locksmith and assembly. The working part of locksmith and assembly screwdrivers for screws and screws with a cross-shaped slot. Dimensions
• GOST 104-83. Replaceable heads. Types and basic sizes (with Changes N 1, 2)
• OST 1 52446-79 Inserts for screws with a cross slot according to GOST 10753-64. Design and dimensions
• OST 1 52448-79 Inserts for screws with a cross slot according to GOST 10753-64. Design and dimensions
• OST 1 52461-01 Replaceable inserts for screws with a cross slot according to GOST 10753-64. Design and dimensions