Types of screws. Types and application of screw fasteners Types of screws

A screw and nut are the most common combination of fasteners. They are found everywhere, from mobile phones to cars and airplanes. A screw is a rod with a knurled thread and a screw-in head made to fit the end face, wrench or screwdriver. The nut has the shape of a ring, the hole of which is equipped with a thread. These fasteners come in different diameters, lengths and shapes.

These fasteners can be found in almost any mechanism consisting of assembled parts. The screw and nut can have different designs, but in most cases they are universal and can be swapped from one mechanism to another. They are used in places where it is necessary to provide a stable tensile connection.

Screw and nut - design features

When examining the design of a screw, you will notice that it is very similar to a bolt. Externally, both of these fasteners are a metal rod with threads over the entire surface and a head with slots for fixing the screwing tool. There is an opinion that their main difference is that the bolt passes through the elements being connected and tightens them when screwed into the nut, and the screw is screwed directly into one of the parts for a connection that has a threaded thread. This statement is fundamentally incorrect, which is confirmed by GOST 27017-86, which directly states that a bolt can be attached either to a nut or to a threaded hole.

The definition in GOST also dispels the statement that a screw is intended to be screwed in with a face or a screwdriver, and a bolt only with a wrench. The only difference between these two elements is their purpose. The screw provides a tensile connection, while the bolt provides a tensile and shear connection. However, in most cases the screw is actually tightened using a screwdriver or edge, while an open-end wrench is rare.

A nut is a ring-shaped fastener with an internal thread designed to be screwed onto a screw, stud or bolt. Its outer side can have a hexagonal shape, intended for use with a regular open-end wrench, square, or with special blades for fingers, the so-called wings.

Types of nuts

Since nuts are used to fasten various elements, they differ not only in size, but also in shape.

The most common types are the following:

• Hexagonal.
• Crowned.
• Cap.
• Lamb.
• Square.
• Splined.
• Eye nut.

Hexagon

The most common type. It is designed to be tightened or loosened using a wrench of any design. Often there is a chamfer along the rim of such fasteners, making it easier to grip with a wrench, which is very important when working in hard-to-reach places.

crown

The form is more rare. Along the outer end of the fastener there are shallow grooves similar to crown teeth. This design is used in those mechanisms where there is a high risk of fasteners self-unscrewing. There is a special hole in the screw shaft into which a pin is inserted, which passes through the groove of the nut, which makes unauthorized unscrewing impossible. To remove such fasteners, you must first manually pull out the pin and then use a wrench.

Cap

The design is used in cases where it is necessary not only to create a reliable connection, but also to disguise it or prevent water from entering its surface. When using the cap type, you don’t have to worry that the thread will rust and there will be difficulties when unscrewing. Such fasteners are often used on furniture. Large size cap nut is used to fix rims on cars.

Lamb

It is considered one of the most convenient types. This design has special blades that allow convenient winding by hand. This screw and nut work without the use of additional tools. The lamb can be found on furniture, as well as in cases where you have to constantly assemble and disassemble, and the key is not always at hand.

Square

Usually inserted into a rectangular groove on the connection piece, which provides fixation without allowing it to rotate. This eliminates the need for additional key retention. This is important when connecting in hard-to-reach places, when it is difficult to reach the nut to hold it. A similar connection is found in sockets for clamping wire cores.

Splined

The design has a round shape with slots selected on the side, perpendicular to the thread. This type can be tightened using a special key. It is mainly used in aircraft manufacturing. There are also special fork screwdrivers for working with small slotted nuts.

Flanged

The design combines a conventional hex nut with an adjacent washer, which increases the pressure area on the attracted surface. This design is intended for connecting parts operating under heavy loads. The washer effectively suppresses vibrations, reducing self-unwinding.

Eye nut

It has a metal ring designed to pass a cable or chain through it. To screw on this type of fastener, simply insert the rod into the ring and tighten it. The screw and nut of the ring structure can be tightened without using a special wrench. You can easily get by with pliers or do everything with your fingers.

Types of screws

Screws come in different thicknesses and lengths. The larger they are, the more reliable the connection they can provide. In addition, they differ from each other in the shape of the heads, as well as in the slots applied to the head.

The shape of the heads is:

• Flat.
• Convex.
• Round.
• Mushroom-shaped.
• Secret.
• Semi-hidden.

Flat screw and nut are the most common types of connections. They are used in places where protruding fasteners do not interfere. First of all, this applies to hidden areas located in the housing of household appliances, cars and other mechanisms.

Convex, round and mushroom-shaped the form is used in visible areas, while the smoothed upper edges easily slide with mechanical contact, which minimizes injuries and does not snag clothing.

countersunk head has a conical shape with a flat top, this type is often found on screws. The head of such a screw is designed to be screwed flush into the surface of the elements being connected, which makes the head almost invisible.

Semi-secret the shape is similar to the secret one, but its top is not flat, but slightly rounded. Such a fastener can also be included in the parts being connected, while a special plastic plug is placed on top, providing protection against corrosion and hiding the fastening.

As for the types of splines, there are more than 20 of them. Many of them are practically not used. The most popular are slots for a straight or Phillips screwdriver. They are used everywhere, from children's toys, computer mice to panels on trains. Socket wrench pliers with four, six, or star-shaped edges are also popular.

Specialized

In addition, there are a lot of unusual shapes that were invented for a special key. A specialized screw and nut are used on proprietary equipment to prevent unauthorized disassembly, which may be prohibited under the terms of the warranty. A prime example of this is the screws used by Apple, which can only be opened with a clover-shaped socket wrench. This type of slot is called Pentalobe.

There are many more similar examples. In most cases, this form is used on small screws, so you can use improvised means to loosen them. Often it is quite possible to get by with a regular flat-head screwdriver, but the slots will be damaged, so for reassembly you will have to replace the screw with a familiar one. If the type of spline pattern is completely unusual, then you can pour superglue into it and insert a suitable screwdriver or socket wrench, which will allow you to unscrew the fastener after gluing. In this case, the screw will also be damaged. Instead of glue, you can use cold welding or molten tin. As a last resort, such a head can be drilled out.

To secure various elements, it is customary to use threaded fasteners. The most common options for such fasteners are a bolt and a screw.

You can buy screws with a semicircular head in specialized stores. But what other types of these products are there?

The most famous types of screws

In the modern world, you can purchase various products, each of which is designed to perform specific functions. The main difference between different types of hardware is the shape of their heads.

• when turning the countersunk screws, the product is camouflaged in the material that was chosen for the job. If there is a hexagonal hole in the head of the product, then you are guaranteed a more effective result of the work done due to the fact that the hardware is very durable and reliable;
• the cylindrical head of the screw remains on the surface of the material, so it is not customary to use it in furniture making. You can opt for hardware with a hexagon located inside;
• There are screws whose heads are semi-cylindrical or semi-circular. Such products may also contain a special hexagon, but most often you can find hardware with a cross-shaped slot.

These types of screws are most often found in modern shops. You can choose one of them depending on the tasks you need to complete.

Features of using screws

To select the appropriate type of screw, many factors must be taken into account. A store consultant will help you sort them out.

If the structural elements are not subject to too much load, then you should choose screws with a cylindrical head. The fact is that a flat-shaped screwdriver will not be able to cope with securing such hardware.

Countersunk head screws are most often used in furniture manufacturing because the finished product looks attractive and aesthetically pleasing. The same hardware has found its application in the housing and public utilities sector.

To securely fix metal sheets, it is necessary to use screws with a semi-cylindrical or semi-circular head. Also, such hardware allows you to secure products in the construction industry.

These are the main features of the use of various types of screws. If you can correctly determine the tasks that need to be completed, then the hardware will perform its main functions efficiently and effectively.

For those who don’t know how a screw differs from a bolt, we suggest watching this video:

It is difficult to imagine the life of modern human society without connecting elements - bolts, nuts, screws, screws and the like. All these seemingly insignificant details surround us everywhere, even in the domestic sphere, not to mention industry and construction. Almost everything - from furniture to a computer - uses some kind of connecting parts. But still, the most common connection elements are bolts.

A bolt is a fastening threaded part that looks like a cylindrical rod. Some part of the bolt has external threads designed to screw on one or more nuts. On one side, this rod is equipped with a head, usually hexagonal in shape, suitable for a wrench. As a rule, bolts are used when assembling dismountable structures. The advantage of this type of connection is that it can be easily replaced if the bolts for any reason fail, or such a need arises.

All types of bolts can be divided into two categories: black and galvanized.

Black bolts are untreated, or do not have an outer coating. They are used in cases where the aesthetic appearance of the structure does not matter, or the product will be painted. For example, untreated bolts are used in mechanical engineering, industrial construction and other similar fields.

Galvanized bolts are used when assembling products in which appearance matters. Such bolts are not subject to corrosion and retain a presentable appearance for a long time. Galvanized bolts are used, for example, when assembling appliances or room furniture.

Also, bolts, whether coated or uncoated, have visual differences between them. Let's look at the main ones.

Types of bolts by size and head shape

Depending on the purpose of the bolt, its head may have one shape or another. The most common types of heads are hexagonal, but there are also square, round and oval.

Head sizes may also vary. For example, a hex head can be either normal, standard size, or reduced or enlarged. The head profile also varies.

Some bolts have a semicircular shape, and there are also bolts that have a round head with a hole inside. There are bolts with a hidden head, for example, for assembling furniture.

Types of bolts according to the shape of the rod

The most common type of rod is a rod of the same diameter along the entire length. But there are also stepped rods, in which the smooth part of the rod is slightly larger in diameter than the part on which the thread is applied. Bolts with this shape of the rod are called tight-fitting and are used to fasten heavily loaded connections.

Also, bolts can be very specific, that is, they are intended for one specific purpose.

Types of bolts by type and thread pitch

Bolts, like nuts, differ from each other and the type of thread. Threads can be metric, inch, trapezoidal, pipe, square, rectangular and thrust. The most applicable is metric thread, which, in turn, is divided into two types: fine and coarse pitch.

Types of bolts by design

An execution option is a design feature defined by a standard, such as GOST or DIN.
For example, in hex bolts, this option may be to lock the threaded connection. To do this, a hole is made on the head of the bolt or, alternatively, at the end of the threaded part for the tying wire or cotter pin.

It also happens that there is a need to reduce the weight of a bolt, while maintaining its size and strength. In such cases, a recess is made in the head of the bolt.

Types of bolts by accuracy class, strength and material

Bolts with a hex head are also classified according to their accuracy class. There are three definitions of accuracy class in total, and they are designated by capital letters “A”, “B” and “C”. Accuracy refers to the degree of thread roughness, the difference in the diameters of cylindrical rods and the supporting surfaces of the heads. Thus, types of bolts with increased accuracy class “A” are used in the most critical assemblies, for example, in precision instrument making.

The difference in diameters between the bolt and the hole does not exceed 0.25 - 0.30 millimeters. The most common accuracy class is “B”. Such bolts are used in holes whose diameter is 1 - 1.5 millimeters larger than the diameter of the bolt rod. For "C" grade bolts, a significant discrepancy between the shank and the hole is allowed. So, the bolt shaft here can be smaller than the hole by up to three millimeters. Such bolts are used for minor connections.

Based on the potential purpose of bolts, different grades of steel are used in their manufacture. Consequently, different types of bolts have different strengths. The following materials are used in their production: steel of ordinary quality; high-quality structural carbon steel; stainless, corrosion-resistant, ordinary steel; stainless, corrosion-resistant, heat-resistant steel; structural alloy carbon steel; low-alloy structural steel for welded structures; heat-resistant relaxation-resistant steel; technical titanium; wrought titanium alloy; copper; brass.

Other types of bolts

The range of use of different types of bolts is very wide. This type of connection has firmly taken its place both at the industrial and household levels. Depending on the scope of use of the bolts, its purpose is also classified. Thus, enterprises producing hardware products produce the following main types of bolts for their intended purpose:

Engineering bolts. A distinctive feature of these types of bolts is their increased strength. They are usually produced with hexagonal head shapes. Threads are usually metric. They are intended primarily for connections that are subject to heavy loads. Area of ​​use: mechanical engineering, instrument making, industrial equipment, as well as assembly of various mechanisms. They are used to connect mainly steel and cast iron parts.

Construction bolts. High-strength materials are also used in their production. They are usually produced with enlarged heads. Such bolts find their use in the construction of various buildings, both civil and industrial. For example, they are used in the assembly of building structures. They are also used in the construction of bridges, tunnels, subways and other important facilities.

Road bolts. The strength class of such bolts varies from low to higher, depending on the location of application. They are made with a semicircular head and a square head - thanks to this they can be tightened without an auxiliary mounting key. They are used in the assembly of metal road barriers. Often these bolts are galvanized to protect them from exposure to weather factors.

Railway bolts. Such fastening connections are produced in small quantities, since the scope of their use is quite small. These types of bolts are used when installing railway tracks and auxiliary structures. In turn, railway bolts are divided into butt (or track), embedded and terminal bolts. Butt (track) bolts are used together with rail pads. They are produced with rounded heads. The anchor bolts are designed to connect sleepers with linings. And with the help of terminal bolts the gasket is attached to the rails. Railway bolts are made from high-strength carbon steel.

Transport (elevator) bolts. Sometimes they are also called elevator bolts. They are designed to attach a bucket or other feeding element to a transport belt. They are made from carbon steel with or without zinc coating. The head of such bolts has its own peculiarity. At the end it is flat, and at the side of the rod it is made in the form of a hemisphere. There are two spikes on the hemisphere that prevent the bolt from rotating around its axis.

Blade bolts. Like railway bolts, such bolts are produced in limited quantities. The scope of their use is agricultural machines. Attachments are secured with plowshare bolts; these can be either metal or wooden elements. They are made with countersunk heads, and in terms of accuracy class, plowshare bolts are produced even with class “C”. They also have a square head that fixes the bolt in one position and prevents it from rotating.

Furniture bolts. As a rule, such bolts are produced with semicircular or countersunk heads. Furniture bolts are cheaper in cost than, say, engineering bolts. They are used not only in assembling furniture, but also in the manufacture of other wooden structures, such as rafters or frame houses. They are often used for other purposes in non-critical connections. The strength level of furniture bolts is usually average. Almost all types of furniture bolts are produced with a galvanized coating for aesthetic reasons.

Despite such a small size and a rather simple principle of operation at first glance, the benefits of screw threads for humanity are difficult to determine. It was the screw that became the factor that gave impetus to the development of science and technology, and many discoveries made by man would have been inaccessible without this simple, yet at the same time so necessary and ingenious invention.

A little history and classification

The design of the screw was known back in Ancient Greece, but at that time this invention was used for the purpose of supplying water, since its blades helped raise water to a certain height. A similar mechanism was also used as presses for wine and oil. The screw mechanism appeared as a fastening element in the 16th century, but it became widespread only in the 19th century. At this time, the bolt was used as a fastening element in construction, as well as in various types of crafts. Bolts gained high popularity in the era of mass production of various mechanisms. Since the advent of the first automobiles, bolts have become an integral part of construction, making structures stronger and more reliable.

There are several types of parts:

• Fasteners. The most common type, which is used to connect parts with the possibility of their detachment. The design consists of a threaded rod at one end of which a head is placed. The head is used to grab a screw with a screwdriver or other tool and then clamp the part. The shape of the head can be very different: round, square, multifaceted, etc. To make it impossible to unscrew the fasteners, heads with a unique shape are created, which requires a special tool.
• Installation. This option is used to fix components in a mutual way. For this purpose, recesses or projections are located at the ends of the bolt for better fixation. The ends of such parts can have different shapes: flat, conical, stepped, cylindrical, ball, embossed, etc.

Scope of application

Screws are widely used in mechanical engineering, construction, agriculture, industry and other fields. Different options are used for different elements, which allows you to achieve specific goals:

• Parts with tapered threads are used for through and blind type holes. Such options are not recommended for use under high dynamic loads, since in this case deformation of the internal thread is possible.
• Flat end bolts can also be used in through-hole and blind fastener applications. In this case, the screwing plane must be perpendicular to the thread axis.
• Parts with a cylindrical pin. This option is only used in blind holes, since it involves less action.

The choice of option depends on several factors, in particular the temperature of the work, vibration indicator, load, etc.

2015

Currently, the use of screws has a wide range. They are primarily used for fastening materials where nails were once used. To speed up the process of driving the latter, special guns are used, but when doing work at home, it is not always rational to use them. It is more profitable and reliable to use screws and screws. They are indispensable for roofing, fastening, finishing and installation work. To facilitate and speed up the fastening process, use electric drills and cordless screwdrivers.

How to choose screws?

There is a sufficient assortment of screws and screws of all colors and sizes, different shapes and models on store shelves. Before purchasing the model you need, you should answer several questions, including:

What material will be joined and its thickness? For example: we are connecting boards of 0.5 and 1 inches (1.25 and 2.5 cm), it is necessary to take screws of at least 1 inch so that the fasteners cover half of the thicker part. Longer fasteners may penetrate through the thickness of the wood.

What tools are used? A screwdriver or drill can be an indispensable assistant. They are also used for drilling pilot holes slightly smaller in diameter than the diameter of the screw. This will make the twisting process easier. The magnetic head (bit) on the screwdriver will allow you to work more comfortably. When choosing a bit, it is necessary that it sits tightly on the slots of the screw. This is necessary to avoid licking the surface of the splines. To fine-tune the fasteners, use a screwdriver. When using a power tool, tighten at low speeds; this will prevent the screw head from breaking and problems with its removal. This happens with brass and stainless steel fasteners.

Types of Screws: Philips is the most common type of screw and has a flat head with a Phillips slot on top. Suitable for outdoor use. Due to this shape of the head, the screw is screwed into the wood until it is flush with it or protrudes slightly. Products for external use are coated with a special coating that protects them from exposure to the atmosphere and gives the screw a gray color. Matte black screws are used indoors.

Types and purpose of screws

Coated screws. Most often, the material from which the fastener is made is determined by the color of the product. These include brass screws. They are perfect for securing door hinges, they are clearly visible and have an aesthetic appearance. Brass screws are a relatively soft metal, so they need to be tightened carefully. The cost of fasteners depends on the quality of the screws manufactured and their coating. Cheap products lose their protective coating when screwed in and then removed; this can lead to the formation of rust spots around the edge and corrosion of the product. This is not significant when fastening boards made of untreated wood. It’s another matter if pressed lumber is fastened together, then the use of cheap screws can lead in the future to their falling out and weakening the structure. Imported universal screws are in great demand; they are also called self-tapping screws. They have a smooth thread surface, unlike Russian-made screws, so they are easier to tighten.

Stainless steel screws. This type of fastener is best used for outdoor work, since there is no need to worry about the coating, and it completely justifies all the expenses for its purchase. The head of these screws has a square recess for mounting them.

Pan head screws. This type of fastening is used as part of the finishing of the surfaces to be joined, because the head of the screw will be visible. The screw head can be convex on the outside and smooth on the inside. Along with the screw, a flat finishing washer made of the same material as the screw is used.

Countersunk head screws. Such product fasteners are used when it is necessary to hide traces of the connection. In such screws, the head is slightly larger than the diameter of the screw itself and has a square recess for tightening. Used for assembling furniture structures.

Blue screws. Used for connecting concrete structures and masonry. They are especially needed for masonry, as they greatly simplify working with it. They have a fairly strong metal structure, but to install them it is necessary to make guide holes using a hammer drill.

The purpose of each type of screw can be found in the instructions for their use:

1. Purpose: for working on metal, chipboard, wood, etc.

2. Product head and coating material: flush, semi-flush; brass, chrome, etc.

3. Quantity per package.

Because of their ease of use, versatility, and durability, screws and screws are a must-have for DIY projects.