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What is a fastener

What are Fasteners Solutions?

Fastener solutions refer to the various types of devices, products, and techniques used to join or secure materials together. These solutions play a crucial role in numerous industries, including construction, automotive, aerospace, and manufacturing.

What is a fastener?

Fastener is an important hardware device, which is used in many engineering related applications to mechanically connect or fix two or more objects together. They are considered as alternatives to welding. Also known as standard parts on the market.

In the manufacturing of machines, fasteners are used to hold two parts together. Fasteners can also be divided into three categories: permanent fasteners, temporary fasteners and semi-permanent fasteners.

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Characteristics of fasteners

Fasteners are mechanical devices that hold two or more parts together. They can be assembled and disassembled at will, allowing for easy removal of the parts without damaging them. Fasteners are generally small in size, light in weight and easy to mass produce. This allows manufacturers to use large quantities of fasteners on a single assembly line with minimal labor costs compared to other types of fastener systems. Additionally, their ease of use means they require little maintenance and therefore have low operating costs over time compared with other systems such as rivets or bolts which require frequent maintenance due to their complexity.”

Materials of Fasteners

There are three main types of steel fasteners used in industry: stainless steel, carbon steel and alloy steel. Main grades of stainless steel fasteners: 200 series, 300 series and 400 series. Titanium, aluminum and various alloys are also common structural materials of metal fasteners. In many cases, special coatings or coatings can be applied to metal fasteners to improve their performance characteristics, such as enhancing corrosion resistance. Common coatings / coatings include zinc, chromium and hot dip galvanizing.

Carbon steel

Carbon steel is a series of carbon and iron alloys, containing up to about 1% carbon and up to 1.65% manganese, and adding a specific amount of deoxidizing elements and residues of other elements.

Low alloy steel

Low alloy steel is a kind of metal mixture composed of steel and other metals, which has ideal properties. Low alloy steel contains about 1% – 5% alloy elements. Therefore, it has precise chemical composition, provides better mechanical properties and aims to prevent corrosion.

Stainless steel

Stainless steel is a general term of the corrosion-resistant alloy steel family containing 10.5% or more chromium. All stainless steels have high corrosion resistance. This resistance to attack is due to the formation of a natural chromium rich oxide film on the surface of the steel.


Brass is a copper-based alloy with the main addition being zinc.


Aluminum is a silvery white metal and the 13th element in the periodic table. A surprising fact about aluminum is that it is the most widely distributed metal on earth, accounting for more than 8% of the mass of the earth’s core. It is also the third most common chemical element on our planet after oxygen and silicon.


Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a malleable metal with very high thermal conductivity and conductivity. Pure copper is soft and plastic; The newly exposed surface is orange red. It is used as a conductor of heat and electricity, building materials, and components of various metal alloys.
The title was provided by our writer.


Titanium is a transition metal light with white silver metal color. It is strong, shiny and corrosion resistant. Pure titanium is insoluble in water, but soluble in concentrated acid. When exposed to high temperatures in the air, this metal forms a passive but protective oxide layer (resulting in corrosion resistance), but it can resist discoloration at room temperature.
The main oxidation state is 4+, although the states of 3+ and 2+ are also known, but they are not very stable. This element burns in air when it is heated to obtain dioxide TiO2 and when it combines with halogen. It reduces water vapor to form carbon dioxide and hydrogen. It reacts in a similar way to hot concentrated acid, but it forms trichloride with chlorohydric acid. The metal absorbs hydrogen to obtain TiH2 and forms nitride tin and carbide tic. Other known compounds are sulfur TiS2, the lowest oxides Ti2O3 and TiO, and sulfur Ti2S3 and tis. Salts are known in all three oxidation states.

Nickel and its alloys

Nickel alloy is an alloy with nickel as the main element. There is complete solid solubility between nickel and copper. The wide solubility range between iron, chromium and nickel makes many alloy combinations possible.

All these materials can be found on a variety of fastener types including screws, rivets, bolts and nuts.  They are used in both structural applications as well as non-structural applications such as fastening accessories to furniture or electronic devices

Types of Fasteners

There are many types of fasteners. The following is a list of the most common:
1. Bolt: it is a fastener composed of head and cylinder, and the screw has external thread. It needs to be used with nuts to fasten and connect two parts with through holes. Bolted connections are removable connections.
2. Stud: it is a fastener without head, and only two ends have external threads. When connecting, one end must be screwed into the part with internal thread hole, the other end must pass through the part with through hole, and then screw on the nut, even if the two parts are closely connected as a whole. Stud connection is also a detachable connection.
3. Screw: it is also a fastener composed of head and screw.
According to the purpose, it can be divided into three categories: mechanical screw, fixed screw and special purpose screw.

  • 1) Mechanical screw: mainly used for fastening connection between parts with fixed threaded holes and parts with through holes.
  • 2) Fixing screw: mainly used to fix the relative position between two parts.
  • 3) Special purpose screws: for example, there are eyebolts for lifting parts.

4. Nut: it has internal thread hole shape, generally flat hexagonal column shape, flat square column shape or flat cylindrical shape. It is used in conjunction with bolts, studs or machine screws to fasten and connect two parts into a whole.
According to its special category, it is divided into two categories: high-strength self-locking nut and nylon self-locking nut.

  • 1) High strength self-locking nut: high strength and good reliability. It is used for road construction machinery, mining machinery, vibration machinery and equipment. It is European technology and less domestic production.
  • 2) Nylon self-locking nut. It is a new type of high seismic and anti loosening fastener, which can be used in various electromechanical products with a temperature of – 50100 ℃. The demand for nylon self-locking nuts in aerospace, aviation, tanks, mining machinery, automobile transportation machinery, agricultural machinery, textile machinery, electrical products and all kinds of machinery has increased sharply, which can prevent major accidents caused by loose fasteners.

5. Self tapping screw: similar to machine screw, but the thread on the screw is the special thread of self tapping screw. It is used to fasten and connect two thin metal components as a whole. This connection is also a detachable connection.
6. Wood screw: it is also similar to machine screw, but the thread on the screw is the special thread of wood screw, which can be directly screwed on wood parts or parts to connect metal or non-metal parts with through holes with wood screws. These parts are fixed together. This connection is also a removable connection.
7. The shape of the washer is a fastener ring. It is placed between the support surface of the bolt, screw or nut and the surface of the connector, which increases the contact surface area of the connector, reduces the pressure per unit area, and protects the surface of the connector from damage. Another elastic washer can also play such a role. It has the function of preventing the nut from loosening.
8. Retaining ring: installed in the shaft groove or hole groove of machinery and equipment to prevent the left and right movement of parts on the shaft or hole.
9. Pin: it is mainly used for the positioning of parts, and some are also used for the connection of parts, fixing parts, transmitting power or locking other fasteners.
10. Rivet: it is a fastener composed of head and handle. It is used to fasten and connect two parts or components with through holes to make them a whole. This connection form is called rivet connection, or riveting for short. It is an inseparable connection.
11. Assembly and connection sub assembly: refers to a combination of supplied fasteners, such as some machine screws or bolts, self provided screws, flat washers or spring washers, and lock washers are supplied in combination. Connecting pair: refers to a fastener supplied by a combination of special bolts, nuts and washers, such as high-strength hexagon head bolt connecting pair for steel structure.
12. Welding nail: it is a heterogeneous fastener composed of light energy and nail head or no nail head, which is fixedly connected to a part or component by welding for connection with other parts.
13. Steel wire screw sleeve: it is a new type of threaded connection element, which is refined from high-strength and high-precision corrosion-resistant diamond wire. Shaped like a spring, it is installed in a specific screw hole of the matrix, and its inner surface forms a standard thread. Matching with the screw bolt can significantly improve the strength and wear resistance of the threaded connection; Especially in aluminum, magnesium, cast iron, plastics and other low-strength materials. The locking type is to add one or more locking rings on the basis of the ordinary type.

Standard of fasteners

The following table is provided for guidance only as there are often dimensional variations between standards.

DIN Standard ISO Standard British Standard Product
DIN 1 ISO 2339   Cone Pins, untempered
DIN 125 ISO 7089   Washers; medium type, primarily for hexagon bolts
DIN 125 ISO 7090   Washers; medium type, primarily for hexagon bolts
DIN 126 ISO 7091   Product grade C washers – designed for use with Hexagon Head Bolts and Nut
DIN 127   BS4464B Spring Lock Washers with square ends or tang ends
DIN 128     Curved and wave Spring Lock Washers
DIN 137     Spring Washers, curved or wave
DIN 1440 ISO 8738   Medium type washers for pins
DIN 1443 ISO 2340   Clevis Pins without head
DIN 1444 ISO 2341   Clevis Pins with head
DIN 1470 ISO 8739   Grooved Pins, full length parallel-grooved with pilot
DIN 1471 ISO 8744   Grooved Pins, full length taper-grooved
DIN 1472 ISO 8745   Grooved Pins, half length taper-grooved
DIN 1473 ISO 8740   Grooved Pins, full length parallel-grooved with chamfer
DIN 1474 ISO 8741   Grooved Pins, half length reverse-grooved
DIN 1475 ISO 8742   Grooved Pins, third length centre-grooved
DIN 1476 ISO 8746   Round Head Grooved Pins
DIN 1477 ISO 8747   Countersunk Head Grooved Pins
DIN 1481 ISO 8752   Spring-type Straight Pins (roll pins) – heavy type
DIN 1587     Hexagon Domed Cap Nuts
DIN 1816     Round Nut with set pin holes inside; ISO metric fine thread
DIN 315     Wing Nuts with rounded wings
DIN 316     Wing Screws with rounded wings
DIN 404     Slotted Capstan Screws
DIN 417 ISO 7435   Slotted Set Screws with long dog point
DIN 427 ISO 2342   Slotted Headless Screws with chamfered end
DIN 428 ISO 4034   Hexagon Nuts, Grade C
DIN 433 ISO 7092   Washers for use with cheese head screws
DIN 433-1 ISO 7092   Product grade A washers – with a hardness up to 250 HV designed for use with cheese head screws
DIN 433-2 ISO 7092   Product grade A washers – with a hardness up to 300 HV designed for use with cheese head screws
DIN 438 ISO 7436   Slotted Set Screws with cup point
DIN 439 ISO 4035 BS3692 Hexagon Thin Nuts
DIN 439 ISO 4036 BS3692 Hexagon Thin Nuts
DIN 439 ISO 8675 BS3692 Hexagon Thin Nuts
DIN 439-1 ISO 4036   Unchamfered Hexagon Thin Nuts – product grade B
DIN 439-2 ISO 4035   Chamfered Hexagon Thin Nuts – product grades A and B
DIN 439-2 ISO 8675   Chamfered Hexagon Thin Nuts – product grades A and B
DIN 440 ISO 7094   Washers for use in timber constructions
DIN 444     Eyebolts
DIN 462     Machine tools; internal tab washers for slotted round nuts for hook spanner according to DIN 1804
DIN 464     Knurled Thumb Screws, high type
DIN 466     Knurled Nuts, high type
DIN 467     Knurled Nuts, low type
DIN 471     Circlips (retaining rings) for shafts; normal type and heavy type
DIN 479     Square Head Bolts with short dog point
DIN 5406     Lock Washers and locking plates for use with rolling bearings
DIN 548     Round Nuts with set pin holes inside
DIN 551 ISO 4766   Slotted Set Screws with flat point
DIN 553 ISO 7434   Slotted Set Screws with cone point
DIN 555 ISO 4034   M5 to M100x6 Hexagon Nuts – product grade C
DIN 558 ISO 4018   Hexagon Head Screws
DIN 580     Collar Eyebolts for lifting purposes
DIN 601 ISO 4016   M5 to M52 Hexagon Head Bolts; product grade C
DIN 603     Mushroom Head Square Neck Bolts
DIN 609     Hexagon Fits Bolts with long thread
DIN 6319     Spherical Washers and conical seats
DIN 6325 ISO 8734   Parallel Pins, hardened: tolerance zone m6
DIN 6340     Washers for clamping devices
DIN 653     Knurled Thumb Screws, low type
DIN 6797     Toothed Lock Washers
DIN 6798     Serrated Lock Washers
DIN 6799     Lock Washers (retaining washers) for shafts
DIN 6900 ISO 10644   Screw and Washer assemblies
DIN 6901 ISO 10510   Tapping Screw and Washer assemblies
DIN 6902 ISO 10673   Plain Washers for screw and washer assemblies
DIN 6903 ISO 10669   Plain Washers for tapping screw and washer assemblies
DIN 6912     Hexagon Socket Thin Head Cap Screws with pilot recess
DIN 6914 ISO 14399-4   High-strength Hexagon Head Bolts with large widths across flats for structural steel bolting
DIN 6916     Round Washers for high-strength structural steel bolting
DIN 6921 ISO 1665   Hexagon Flange Bolts
DIN 6922 ISO 1665   Hexagon Flange Bolts with reduced shank
DIN 6923 ISO 1661   Hexagon Nuts with flange
DIN 6924 ISO 7040   Prevailing torque type Hexagon Nuts with non-metallic insert
DIN 6924 ISO 10512   Prevailing torque type Hexagon Nuts with non-metallic insert
DIN 6925 ISO 7042   Prevailing torque type all-metal Hexagon Nuts
DIN 6925 ISO 10513   Prevailing torque type all-metal Hexagon Nuts
DIN 6926 ISO 7043   Prevailing torque type Hexagon Nuts with flange and with non-metallic insert
DIN 6926 ISO 12125   Prevailing torque type Hexagon Nuts with flange and with non-metallic insert
DIN 6927 ISO 7044    Prevailing torque type All-Metal Nuts with flange
DIN 6927 ISO 12126    Prevailing torque type All-Metal Nuts with flange
DIN 7045     Pan Head Screws with type H or type Z cross recess – product grade A
DIN 7337 ISO 14589   Break mandrel Bblind Rivets
DIN 7337 ISO 15977 to ISO 15984   Break mandrel Blind Rivets
DIN 7337 ISO 16582 to ISO 16584   Break mandrel Blind Rivets
DIN 7343 ISO 8750   Spiral Pins; normal type
DIN 7344 ISO 8748   Spiral Pins; heavy duty type
DIN 7346 ISO 13337   Spring-type Straight Pins; (roll pins) lightweight type
DIN 7349     Plain Washers for Bolts with heavy clamping sleeves
DIN 7500-1 ISO 7085   Thread rolling Screws for metric ISO thread – Part 1: Types, designation, requirements
DIN 7500-2     Thread rolling Screws for ISO metric thread; guideline values for hole diameters
DIN 7504     Self-drilling Screws with tapping screw thread – dimensions, requirements and testing
DIN 7513     Hexagon Head and slotted head thread cutting screws – dimensions, requirements and testing
DIN 7516     Cross recessed head thread cutting screws – dimensions, requirements and testing
DIN 7603     Ring Seals and Gaskets
DIN 7970 ISO 1478   Threads and thread ends for tapping screws (modified version of ISO 1478)
DIN 7971 ISO 1481 BS4174 Slotted Pan Head Tapping Screws
DIN 7972 ISO 1482   Slotted Countersunk Head Tapping Screws
DIN 7973 ISO 1483   Slotted Raised Countersunk Head Tapping Screws
DIN 7977 ISO 8737   Taper Pins with thread ends and constant point lengths
DIN 7978 ISO 8736   Taper Pins with internal thread
DIN 7979 ISO 8733   Parallel Pins with internal thread
DIN 7979 ISO 8735   Parallel Pins with internal thread
DIN 7980   BS4464A Spring Lock Washers with square ends for cheese head screws
DIN 7981 ISO 7049   Cross Recessed Pan Head Tapping Screws
DIN 7982 ISO 7050   Cross Recessed Countersunk Head Tapping Screws
DIN 7983 ISO 7051   Countersunk (flat) Head Tapping Screws with cross recess
DIN 7984     Hexagon Socket Thin Head Cap Screws
DIN 7985 ISO 7045 BS4183 Cross recessed raised Phillips Pan Head Screws
DIN 7989-1     Washers for steel structures – product grade C
DIN 7989-2     Washers for steel structures – product grade A
DIN 7991 ISO 10642 BS4168 Hexagon Socket Countersunk Head Cap Screws
DIN 84 ISO 1207 BS4183 Product grade A Slotted Cheese Head Screws
DIN 85 ISO 1580 BS4183 Product grade A Slotted Pan Head Screws
DIN 9021 ISO 7093   Plain Washers with large outside diameter
DIN 908     Hexagon Socket Screw Plugs with parallel screw thread
DIN 910     Hexagon-duty hexagon Head Screw Plugs
DIN 911 ISO 2936   Hexagon Socket Screw Keys
DIN 912 ISO 4762 BS4168 Hexagon Socket Head Cap Screws (modified version of ISO 4762)
DIN 912  ISO 21268 BS4168 Hexagon Socket Head Cap Screws (modified version of ISO 4762)
DIN 913 ISO 4026   Hexagon Socket Set Screws with flat point (ISO 4026 modified)
DIN 914 ISO 4027   Hexagon Socket Set Screws with cone point (ISO 4029 modified)
DIN 915 ISO 4028   Hexagon Socket Set Screws with full dog point
DIN 916 ISO 4029   Hexagon Socket Set Screws with cup point (ISO 4029 modified)
DIN 918-3     Overview of European standards for fasteners
DIN 921     Slotted Pan Head Screws with large head
DIN 923     Slotted Pan Head Screws with shoulder
DIN 929     Hexagon Weld Nuts
DIN 93     Tab Washers with long tab
DIN 930     Fine thread pitch partially Threaded Screws
DIN 931-1 ISO 4014 BS3692 M1,6 to M39 Hexagon Cap Screws partially threaded – product grades A and B
DIN 931-2 ISO 4014 BS3692 M42 to M160x6 Hexagon Cap Screws partially threaded – product grade B
DIN 933 ISO 4017 BS3692 M1,6 to M52 Hexagon Cap Screws fully threaded – product grades 8.8
DIN 934 ISO 4032   Hexagon Nuts with metric coarse and fine pitch thread – product classes A and B
DIN 934 ISO 8673   Hexagon Nuts with metric coarse and fine pitch thread – product classes A and B
DIN 935-1     Hexagon Slotted Nuts and Castle Nuts with metric coarse and fine pitch thread – product grades A and B
DIN 935-2     M42 to M160x6 Hexagon Head Bolts; product grade B
DIN 935-3     Hexagon Slotted Nuts with metric coarse pitch thread – product grade C
DIN 936   BS3692 M8 to M52 and M8x1 to M52x3 hexagon thin nuts; product grades A and B
DIN 937     Hexagon Thin Castle Nuts
DIN 938     Studs with a length of engagement equal to about 1 d
DIN 939     Studs with a length of engagement equal to about 1,25 d
DIN 94 ISO 1234   Split Pins
DIN 95     Slotted Raised Countersunk (oval) Head Wood Screws
DIN 96     Slotted Round Head Wood Screws
DIN 960 ISO 8765   M8x1 to M100x4 Hexagon Head Bolts with fine pitch thread – product grades A and B
DIN 960 ISO 8676   M8x1 to M100x4 Hexagon Head Bolts with fine pitch thread – product grades A and B
DIN 961 ISO 8676   M8x1 to M52x3 Hexagon Head Bolts with fine pitch thread – product grades A and B
DIN 962     Designation system for fasteners
DIN 963 ISO 2009 BS3692 Slotted Countersunk Head Screws (with countersunk heads as specified in ISO 2009-1972)
DIN 964 ISO 2010 BS3692 Slotted Raised Countersunk Oval Head Screws
DIN 965 ISO 7046 BS3692 Cross Recessed Countersunk Flat Head Screws
DIN 966 ISO 7047   Cross Recessed Raised Countersunk Head Screws
DIN 970 ISO 4032   Hexagon Nuts; style 1; metric coarse thread, product grades A and B; ISO 4032 modified
DIN 971-1 ISO 8673   Style 1 Hexagon Nuts with metric fine pitch thread; property classes 6 and 8
DIN 971-2 ISO 8674   Style 2 Hexagon Nuts with metric fine pitch thread; property classes 10 and 12
DIN 972 ISO 4034   M5 to M39 Hexagon Nuts; style 1; product grade C (modified version of ISO 4034)
DIN 975     Threaded Rods
DIN 976-1     Metric thread Stud Bolts
DIN 976-2     Metric interference-fit thread Stud Bolts
DIN 977 ISO 21670   Hexagon Weld Nuts with flange
DIN 979     Hexagon Thin Slotted Nuts and Castle Nuts with metric coarse and fine pitch thread – Product grades A and B
DIN 980 ISO 7042   All-metal prevailing torque type Hexagon Nuts
DIN 980 ISO 10513   All-metal prevailing torque type Hexagon Nuts
DIN 981     Locknuts for use with rolling bearings
DIN 982 ISO 7040   Prevailing torque type Hexagon Nuts with non-metallic insert
DIN 982 ISO 10512   Prevailing torque type Hexagon Nuts with non-metallic insert
DIN 983     Retaining Rings with lugs for use on shafts (external circlips)
DIN 985 ISO 10511   Prevailing torque type Hexagon Thin Nuts with non-metallic insert
DIN 986     Prevailing torque type Hexagon Domed Cap Nuts with non-metallic insert
DIN 988     Shim Rings and supporting rings

Uses of Fasteners

Fasteners are used in applications where holding power is required.Fasteners are mechanical units used to connect two or more objects. Fasteners can be used for permanent or temporary connections, depending on site conditions. There are many types of fasteners that have different applications and people should certainly know.
Fasteners can be divided into permanent or temporary units.
Examples of permanent fasteners can be rivets, nails, etc., which are disposable fasteners designed to permanently connect two objects. Therefore, these fasteners cannot be removed once installed, and removing it may cause damage to it. Temporary fasteners are designed to temporarily connect two or more objects and can be easily removed and reused.
Examples of temporary fasteners are bolts and screws, which are commonly used in some industries and products because they allow components to be reassembled when needed. Temporary fasteners are also called threaded or unthreaded.
From household appliances commonly used in our daily life to some high-tech gadgets, we all have a common component, that is fasteners. Although fasteners are not directly imagined by us, they will play an important role in our routine life. Whatever it is, from the tables and chairs we sit on to the cars we travel, because every edge we use is fixed in place by fasteners. Fasteners can be used in various industries, such as automobile, petrochemical, pharmaceutical, oil and natural gas, rubber, food processing, heavy machinery and so on.

Identification and inspection of threads

The use and characteristics of threads.

Threads are used in a wide range of applications, from airplanes and automobiles to water pipes and gas used in our daily lives, most threads are used for fastening connections, followed by force and motion transmission, and some specialized threads.
The use of threads has endured because of their simple structure, reliable performance, ease of disassembly and ease of manufacture, making them an indispensable structural element in various electromechanical products today.
According to the use of threads, all kinds of threaded parts should have the following two basic functions: first, good spinability; second, sufficient strength.

Classification of threads

a. There are four major categories according to their structural characteristics and uses:

  • Common thread (fastening thread): The thread is triangular in shape and is used to connect or fasten parts. The common thread is divided into coarse thread and fine thread according to the pitch, and the connection strength of fine thread is higher.
  • Transmission threads: The threads are trapezoidal, rectangular, saw-shaped and triangular in shape.
  • Sealing threads: Used for sealing connections, mainly pipe threads, tapered threads and tapered pipe threads.
  • Special-purpose threads, referred to as special threads.

b. Threads can be divided into metric threads (metric threads), English threads, American threads, etc. We customarily refer to English threads and American threads collectively as English threads, which have a tooth angle of 60°, 55°, etc. The thread parameters such as diameter and pitch use the English size (inch). In our country, the thread angle is 60°, and the diameter and pitch in millimeters (mm) are used.

Basic terminology of threads

  • Thread: A continuous protrusion with a specified thread pattern along the spiral line on a cylindrical or conical surface.
  • External thread: The thread formed on the external surface of a cylinder or cone.
  • Internal thread: The internal thread formed on the inner surface of a cylinder or cone.
  • Major diameter: The diameter of an imaginary cylinder or cone tangent to the top of the male thread or the bottom of the female thread.
  • Minor diameter: The diameter of an imaginary cylinder or cone tangent to the bottom of the external thread or the top of the internal thread.
  • Median: The diameter of an imaginary cylinder or cone whose bus bar passes through a groove and a projection of equal width on the tooth pattern. This hypothetical cylinder or cone is called a median cylinder or median cone.
  • Right-hand thread: A thread that is screwed in when rotated clockwise.
  • Left-hand thread: A thread that is screwed in when rotated counterclockwise.
  • Tooth angle: The angle between two adjacent tooth sides on a thread tooth pattern.
  • Pitch: The axial distance between two points on the mid-diameter line of two adjacent teeth.

Marking of threads

Metric thread markings:
In general, a complete metric thread marking should include the following three aspects:

  • a. The thread type code indicating the characteristics of the thread;
  • b. Thread size: Generally, the diameter and pitch should be included, and for multi-threads, the lead and thread number should be included;
  • c. Accuracy of the thread: The accuracy of most threads is determined by the tolerance zone (including the position and size of the tolerance zone) of each diameter and the length of the spin.

Thread measurement

For standard threads, the thread ring gauge or plug gauge is used to measure the thread.
Since there are many thread parameters, it is impossible to measure each one of them individually. It is convenient and reliable, and has become the most common method of acceptance in actual production because it is comparable to the accuracy requirements of ordinary threads.

Thread measurement (middle diameter)

In a threaded connection, only the median size determines the nature of the thread fit, so it is critical to determine whether the median size is properly qualified. Based on the fact that the median size should ensure that the most basic performance of the thread is achieved, the standard stipulates the principle of judging the median qualification, namely: “The actual thread’s operational median cannot exceed the median of the largest solid tooth type. And the single median diameter of any part of the actual thread cannot exceed the median diameter of the smallest solid tooth type.”
There are two convenient methods to measure the single mid-diameter, one is to measure the mid-diameter with a thread mid-diameter micrometer, and the other is to use the three-pin method (our company uses the three-pin method).

Thread fit grade

The thread fit is the size of loose or tight between the screwed threads, and the grade of the fit is the combination of deviation and tolerance specified on the internal and external threads.
(1) For unified imperial threads, there are three thread grades for external threads: 1A, 2A and 3A, and three grades for internal threads: 1B, 2B and 3B, all of which are clearance fits. The higher the grade number, the tighter the fit. In imperial threads, deviations are specified only for grades 1A and 2A, with zero deviation for grade 3A, and the deviations are equal for grades 1A and 2A.
The larger the grade number the smaller the tolerance, as shown in the figure:

  • 1) Class 1A and 1B, very loose tolerance grades, which are applicable to the tolerance fit of internal and external threads.
  • 2) Class 2A and 2B, the most common thread tolerance class specified for imperial series mechanical fasteners.
  • 3) Grades 3A and 3B, the tightest fit for tight tolerance fasteners, are used for safety-critical designs.
  • 4) For external threads, Class 1A and 2A have a fit deviation, while Class 3A does not. Class 1A tolerance is 50% greater than Class 2A tolerance and 75% greater than Class 3A, and for internal threads, Class 2B tolerance is 30% greater than 2A tolerance. Class 1B is 50% greater than Class 2B and 75% greater than Class 3B.

(2) For metric threads, there are common thread grades for external threads: 4h, 6e, 6g and 6h, and for internal threads: 6G, 6 H and 7H. (Japanese standard thread accuracy grades are divided into three levels: I, II and III, and the usual condition is grade II.) In metric threads, the basic deviation of H and h is zero. the basic deviation of G is positive, and the basic deviation of e, f and g is negative. As shown in the figure:

  • 1) H is a common tolerance zone position for internal threads, and is not generally used as a surface coating or with a very thin phosphate layer. g position basic deviation is used for special occasions, such as thicker coatings, and is generally rarely used.
  • 2) g is commonly used to plating 6-9um thin plating, such as product drawings require 6h bolt, its thread before plating using the tolerance band of 6g.
  • 3) The thread fit is best combined as H/g, H/h or G/h. For the thread of refined fasteners such as bolts and nuts, the standard recommendation is to use a 6H/6g fit.

Medium accuracy grade for common threads
Nut: 6H
Bolt: 6g
Medium accuracy grade for threads with thick cover
Nuts: 6G Bolts: 6e
High-precision grade
Nuts: 4H Bolts: 4h , 6h

Types and structure of steel structure bolts

Steel Structure Bolt Connection

Steel structure bolting is a connection method to connect two or more steel structure parts or members with bolts to become one. Bolt connection is the easiest way to connect the components in pre-assembly and structural installation.
Bolted connections were first used in the installation of metal structures, and in the late 1830s, bolted connections were gradually replaced by riveted connections, which were only used as temporary fixing measures in the assembly of members. high strength bolting methods emerged in the 1950s. High-strength bolts are made of medium carbon steel or medium carbon alloy steel, and their strength is 2-3 times higher than ordinary bolts. High-strength bolt connection has the advantages of easy construction, safety and reliability, and began to be used in the manufacture and installation of steel structures in some metallurgical plants after the 1960s.

Specifications of bolts

Bolt specifications commonly used in steel structures are M12, M16, M20, M24, M30, M is the bolt symbol, the number is the nominal diameter.
Bolts in accordance with the performance level of 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9 a total of ten grades, of which more than 8.8 grade bolt material for low-carbon alloy steel or medium carbon steel and heat treatment (quenching, tempering), commonly known as high-strength bolts, 8.8 grade below (excluding 8.8 grade, refined ordinary bolts also contain 8.8 grade) Generally known as ordinary bolts. The following table shows the performance grade and mechanical properties of bolts.
The bolt performance grade number consists of two parts, which indicate the nominal tensile strength of the bolt and the flexural strength ratio of the material. Such as the performance level of 4.6 bolts means: the first part of the number (“4” in 4.6) for the nominal tensile strength of the bolt material (N/mm2) 1/100, that is, fu ≥ 400N/mm2; the second part of the number (“6” in 4.6) “) for the bolt material yield strength ratio of 10 times, that is, fy/fu = 0.6; the product of the two parts of the number (4 × 6 = “24”) for the nominal yield point (or yield strength) of the bolt material (N/mm2) of 1/10, that is, fy ≥ 240N/mm2.
Ordinary bolts of steel structure can be divided into three grades according to the production accuracy: A, B and C. A and B grade are refined bolts, which are generally used for mechanical products, and C grade are rough bolts. Unless otherwise specified, ordinary bolts of steel structure are generally ordinary rough-made C grade bolts with performance grade 4.6 or 4.8.
The strength design value of the bolt connection using GB50017-2003 “Steel Design Code” Table 3.4.1-4 take value.

The classification of bolts

Bolts in a broad sense, including ordinary bolts, high-strength bolts, foot anchors, expansion bolts, chemical anchors, screws, pins, etc.; bolts in a narrow sense are divided into ordinary bolted connections and high-strength bolts.
1) Ordinary bolt connection
Ordinary bolts are divided into rough bolts and fine bolts according to the production accuracy.
Ordinary bolts can be divided into hexagonal head bolts, double head bolts, countersunk head bolts according to the form.
Rough bolts
C-level bolts are generally rough bolts, made of carbon structural steel. In order to make the bolts penetrate into the screw holes smoothly, the aperture should be 1.0-2.0mm larger than the nominal diameter d of the bolts, which is a class II hole. The bolt hole spacing arrangement should be convenient for the wrench to tighten the nut. When the rough bolt is used to connect the members of the column, beam and roof frame, the connection structure with the pallet should be used. At this time, the bolt is in tension and the shear force is carried by the pallet (as shown below).
The low strength grade of the material used in the rough bolt limits the scope of its use in the structural connection, but it is still widely used in the connection of the secondary beam of the working platform, the wall skin beam, the roof beam and the support, the articulated support, etc., where the shear force is small.
Rough bolts are also commonly used for pre-assembly of steel structures in plants, pre-tightening of riveted members before riveting, and temporary tightening before assembly and welding of installation nodes before high-strength bolts are connected. When rough bolts are used as permanent fixing bolts, they need to be tightened and anti-loosening measures taken after alignment.
Refined bolts
Grade A and B bolts are refined bolts, and the holes are generally Class I. The aperture should be 0.3-0.5mm larger than the nominal diameter of the bolt d. Refined bolts are used for some structural connections that are often disassembled and cannot be riveted. Refined bolts are generally used for mechanical products, and are rarely used in construction steel structures.
2) High-strength bolt connection
Bolts made of high-strength steel or bolts that require a large preload can be called high-strength bolts. High-strength bolts apply pre-tension and transmit external force by friction. Ordinary bolt connection by the bolt rod shear and hole wall pressure to transmit shear, tighten the nut when the pre-tension is very small, the impact can be negligible, while high-strength bolts in addition to its high material strength, but also to the bolt to apply a lot of pre-tension, so that the connection between the members of the squeezing pressure, so that there is a great deal of friction perpendicular to the direction of the screw, and pre-tension, anti-slip coefficient and the type of steel have a direct impact on the high-strength bolts. load-bearing capacity.
High-strength bolts are divided into two main types according to their stress conditions: friction type and pressure type.
High strength bolts are divided into two types according to the construction process: torsional shear type high strength bolts and large hexagonal high strength bolts.
Friction type high-strength bolts are connected by the friction force generated on the contact surface of the steel plate after the tightening pressure of the bolts makes the connection plate layer tight to transfer the external force. The surface of the component is sandblasted to produce a red rust surface, which can obtain a larger friction coefficient and reduce the number of connecting bolts. The aperture of friction type high strength bolts should be 1.5-2.0mm larger than the nominal diameter d of the bolts.
The hole diameter should be 1.0-1.5mm larger than the nominal diameter of the bolt d. The holes are drilled by CNC drilling machine and drilling die.
In short, friction type high-strength bolts and pressure type high-strength bolts are actually the same kind of bolts, the difference lies in whether the design takes into account the slip. Design, friction type high strength bolts friction surface can not slide, the screw does not bear shear, once the friction surface slip, it is considered to reach the design damage state, technically more mature and reliable; pressure type high strength bolts friction surface can slide, the screw also bear shear, the final damage and ordinary bolt damage the same (bolt shear bad or steel plate crush bad).
Large hexagonal high-strength bolts, from a high-strength bolt, a nut and two washers can form a high-strength bolt connection vice.
During construction, the structure is temporarily fixed with rough bolts, and after the structure is installed and corrected, the rough bolts are replaced with high-strength bolts one by one starting from the middle of the bolt group and the initial screwing is carried out, and then the re-screwing and final screwing are carried out in sequence after the initial screwing.
When installing high strength bolts with large hexagonal head, a washer should be added on each side of the bolt. The initial screwing torque value is 50% of the final screwing torque value, the re-screwing torque value is equal to the final screwing torque value, the final screwing torque value calculation formula is: Tc=K*Pc*d. Tc is the final screwing torque value, unit N-m; K is the torque coefficient; Pc is the construction pre-tension, unit kN; d is the high strength bolt thread diameter, unit mm. torque wrench is used for screwing, torque correction should be made before each use.
Torsional shear high-strength bolts, a high-strength bolt, a nut and a washer form a torsional shear high-strength bolt connection
When installing torsion shear high strength bolts, only one washer should be added on the side of the nut. The formula for calculating the initial torque value is: Tc=0.065*Pc*d. Tc is the initial torque value, unit N-m; Pc is the construction pretension, unit kN; d is the diameter of the thread of the high-strength bolt, unit mm. The final screwing is done by using a special wrench to break the end of the plummer head. The focus of quality inspection should be on the supervision and inspection of the construction process.
3) Footing anchor bolts
Footing anchor bolts, alias footing bolts, footing screws, footing wires, etc., are used for the connection of steel structure footing and concrete foundation components. It is generally made of Q235 and Q345 round steel.
Different kinds of footing anchor bolts (diameter greater than 24mm should be used in the form of anchor plate)
The footing anchor bolt group is fixed by the steel frame during installation, installed together with the tied steel cage, and then concrete is poured, and the bolt head should be exposed to the concrete surface for a certain length. After the concrete reaches a certain strength, install the steel column footing, and finally the second grouting at the bottom of the column.
4) Chemical anchor bolts
Chemical anchor bolt is a new type of fastening material, which consists of chemical agent and metal rod body. It is used to install connections of other structures on the completed concrete structure. It can be used in the installation of various steel structures, curtain walls, marble dry hanging construction after the addition of buried parts, but also for equipment installation, highway, bridge guardrail installation, building reinforcement and transformation.
Chemical anchor is a new type of anchor after the expansion anchor, is through the special chemical adhesive, the screw gluing fixed in the concrete substrate drilling, in order to achieve the anchoring of the fixed parts of the composite parts. Because the chemical anchor bolt has a large pullout capacity, it can replace the embedded anchor reinforcement, and is often used in the construction site to forget to install the steel pre-buried parts but the concrete has been poured, with the later addition of the chemical anchor bolt embedded parts to remedy.
The construction steps of chemical anchor bolts are as follows:

  • According to the engineering design requirements, drill holes in the base material (e.g. concrete) at corresponding locations. The hole diameter, hole depth and bolt diameter should be determined by professional technicians or field tests.
  • Drill the hole with impact drill or water drill.
  • Clean up the dust in the drilling with special air cylinder, brush or compressed air machine, it is recommended to repeat no less than 3 times, there should be no dust and open water in the hole.
  • Make sure the surface of the bolt is clean, dry and free of oil plaster.
  • Make sure the glass tube anchor package is free from any abnormalities such as broken appearance and solidification of chemicals, put the round head facing outward into the anchor hole and push it to the bottom of the hole.
  • Use electric drill and special installation jig to insert the screw to the bottom of the hole with strong rotation, and do not use impact method.
  • When rotating to the bottom of the hole or the marked position on the bolt, stop rotating immediately and remove the installation jig. Avoid disturbing after the gel until it is completely cured. Overtime rotation leads to loss of glue and affects anchoring force. (Rotation time should not exceed 30 seconds, rotation speed should not be less than 300 rpm and not more than 750 rpm, bolt advance speed is about 2cm/sec, impact is not allowed)

5) Expansion bolts
The role of expansion bolts is the same as the role of chemical anchor bolts, used for anchorages with less force.
No expansion bolts shall be used in the parts of concrete structure with cracks and parts prone to cracks. At the same time, the main load-bearing structures, important pipelines and high-speed operation, impact loading and vibration of the design of the expansion bolts, should be calculated according to the design of the tensile force and the design of the shear force to choose a larger specifications.

The arrangement of bolts and construction requirements

Bolt arrangement is divided into two kinds of parallel and staggered:

  • Side by side – simple, neat and compact used to connect the plate size is small, but the member cross-section weakening large;
  • Staggered – arrangement is not compact, the size of the connection plate used is large, but the cross-sectional weakening of the member is small.

Force requirements

  • Vertical force direction: in order to prevent the bolt stress concentration from affecting each other, the cross-sectional weakening is too much and reduces the bearing capacity, the edge distance and end distance of the bolt cannot be too small;
  • With the direction of force action: in order to prevent the plate from being pulled or sheared off, the end distance cannot be too small;
  • For compressed members: to prevent bulging of the connecting plates, the middle distance cannot be too large.

Structural requirements

The edge distance and the middle distance of the bolts should not be too large, so as to avoid poor fit between the plates and moisture intrusion and corrosion of the steel.

Construction requirements

  • In order to facilitate the tightening of nuts by wrenches, the middle distance of bolts should be not less than 3do;
  • According to the above requirements, GB50017-2017 Steel Structure Design Code gives the allowable spacing of bolts and related design values.

Manufacturing process of fasteners

There are different types of fasteners. These include:

  • 1. Coil element: Small billets are used as raw material, heated and rolled to make coiled elements, also known as wire or coil.
  • 2. Annealing: A metal heat treatment process in which metal is slowly heated to a certain temperature for sufficient time, and then cooled at an appropriate rate (usually slow cooling, sometimes controlled cooling).
  • 3. Pickling: A process of cleaning metal surface with acid solution to remove oxide layer and rust on metal surface.
  • 4. Phosphating treatment: It is a process of forming phosphide chemical conversion film through chemical and electrochemical reaction. The function of phosphating film is to basically protect the metal, prevent the metal from corrosion, and prevent friction and lubrication at the same time. It belongs to surface treatment. Pretreatment.
  • 5. Saponification: refers to the hydrolysis reaction process of oil products catalyzed by alkali. The function of saponification is to further increase the lubrication performance of metal surface, which also belongs to the pretreatment of surface treatment.
  • 6. Stretch. The pretreated wire is extruded into the required shape (including appearance and material diameter) with a disc die with appropriate wire diameter.
  • 7. Cold heading: a forging method in which a die is used to extrude a metal rod at room temperature. It is usually used to manufacture screws, bolts, rivets and nuts, which can reduce or replace cutting.
  • 8. Turning: It is a kind of machining, which mainly uses turning equipment to turn the workpiece blank to obtain the ideal workpiece shape.
  • 9. Thread processing (threading, rolling and tapping): Threads are obtained by extruding or cutting the material.
  • 10. Heat treatment: the comprehensive process of heating, heat preservation and cooling the material in a certain medium, and controlling its performance by changing the surface or internal structure of the material.
  • 11. Surface treatment. It refers to the process of artificially forming a surface layer with different mechanical, physical and chemical properties from the substrate on the surface of basic materials. Its purpose is to meet the requirements of corrosion resistance, wear resistance, decoration or other special functions of the product. We often hear hot-dip galvanizing, blue white zinc plating, bluing, blackening, etc. These are surface treatment processes.

Fastener Coatings and Finishes

Fasteners are available with various coatings and finishes to enhance their performance, appearance, and longevity. Some popular options include:

  • Zinc Plating: Offers corrosion resistance and is ideal for indoor applications.
  • Galvanized Coating: Provides excellent corrosion protection, making it suitable for outdoor and harsh environments.
  • Black Oxide: Improves the appearance and adds a layer of corrosion resistance to fasteners.
  • Nickel Plating: Enhances corrosion resistance and provides a decorative finish.

Packing of fasteners

How to Pack Fasteners

Packaging fasteners is a delicate process that requires skill, caution and attention to detail.
It’s important to remember that packaging can be an extra expense for your company, so it’s important to accurately understand your needs. You don’t want to spend money on unnecessary packaging materials or services.
The best way to pack fasteners is to use a vacuum bag system. This method uses heat and pressure to seal the bags around your products to form a custom, airtight seal to protect them from damage during transportation. The bagging system also helps to protect the product from moisture so that it will not rust or corrode during storage.
You can also choose to use shrink wrapping machine to achieve this purpose. This machine seals the plastic on the edge of the product so that it will not be damaged by moisture entering the container during transportation or storage.
Packaging fasteners are a key part of any order fulfillment process. If you don’t know how to pack the fasteners correctly, you may eventually cause damage to the goods or even litigation.
In order to pack the fasteners correctly, you need to use bubble film and air bag to prevent them from shifting during transportation. You should also use packaging peanuts or other cushioning materials, such as paper or foam, to prevent items from rubbing against each other during transportation, which will cause damage over time. It is also important that your packaging materials be clean so that they do not get dirty during storage or transportation.
When you package fasteners in batches, make sure each has its own space so that they will not be damaged during transportation or storage.

Quality inspection of fasteners

How to check fasteners?

The first step in checking fasteners is to identify them properly. There are several different types of fasteners that have different characteristics, so it’s important not to confuse them with each other. After you’ve identified the type of fastener you’re working with, make sure it’s rated for high-quality use by checking its specifications sheet or contacting the manufacturer directly.
If you’re working with a new type of fastener for the first time (or if you want to get more information on how something works), there are plenty of online resources available to help you learn more about them before using them on any project.
When you’re inspecting fasteners, look for the following:

  • 1. The heads of screws should be flat and smooth.
  • 2. The threads on the bolts should be clean and even throughout their length.
  • 3. The ends of all bolts should be smooth and free of burrs or cracks that could cause them to break off in use.

Surface inspection: This is the simplest, most common form of quality inspection. Inspectors will examine a fastener to check for defects, such as pitting or scratches, before it leaves the factory.

Dimensional inspection: This type of quality control involves measuring various dimensions to ensure that they fall within a small tolerance range. For example, if a bolt has been tightened too much during assembly, its diameter will be smaller than expected because it’s compressed from both sides and not just from one side like when you tighten a nut onto a bolt by hand.
Chemical analysis: A machine called an X-ray fluorescence analyzer can detect trace elements present in steel alloys at very low levels—this is useful for detecting impurities like lead or sulfur which would make your fastener less corrosion resistant and more likely to fail prematurely due to stress corrosion cracking (SCC) between two surfaces sharing an electrolyte-containing fluid interface (like salt water). Chemical analysis can also reveal other types of contaminants such as manganese content so we know whether our alloy contains too much manganese which makes it brittle when hardened rather than tough like chrome molybdenum steels should be used instead

Measurement of fasteners

When you’re measuring fasteners, there are a few factors to consider. You’ll need to know the length and diameter of each fastener before you can proceed with anything else. Once you have those numbers, though, it’s time to look at standards.

Many different types of fasteners exist and have been developed over time depending on what they’re being used for and what type of materials they’re going into or coming out of. For instance, if your project requires high-strength bolts that will resist corrosion from salt water exposure then perhaps these three grades would be ideal: Grade 8 (200 ksi), Grade 10 (350 ksi), Grade 12 (500 ksi). The higher the grade number is means greater tensile strength capabilities so these grades would provide much better protection against corrosion than lower grade options such as 5/16th inch flathead lag screws rated for 150 pounds per inch; use this only if no other option were available!

How to improve the quality of fasteners

When it comes to the quality of fasteners, there are many factors that affect the quality of a product.

  • Supply chain management
  • Process control
  • Quality control
  • Selection of raw materials
  • Technological improvement
  • Advanced equipment
  • Staff training
  • Customer feedback

Cost of fasteners

The cost of fasteners depends on the raw material and the labor cost. The exchange rate between USD and RMB affects the cost of fasteners.

How to Choose Industrial Fasteners

What should you be looking for in a fastener? Here are a few things to consider.

  • 1. Strength.
  • 2. Brittleness.
  • 3. Corrosion resistance.
  • 4. Electrical coupling corrosion performance.
  • 5. Cost.

When selecting fasteners for industrial applications, a variety of factors and characteristics must be considered, including:

  • The type of thread.
  • The applied load on the fastener.
  • The stiffness of the fastener.
  • The number of fasteners required.
  • Accessibility.
  • Environmental factors (meaning temperature, water exposure and potential corrosion factors).
  • Installation process.
  • Material to be connected.
  • Reusability.
  • Weight limitations.

Fasteners can sometimes be supplied with coatings (e.g. cadmium plated, zinc plated, phosphate plated) to improve their corrosion resistance and general performance.

How to find reliable fastener manufacturers

To get the best fastener manufacturers, you’ll want to find out:

  • The reliability of each manufacturer. To do this, ask for a certificate of quality and check the manufacturer’s website for information about its certification. You can find information on third-party inspections and payment terms there as well.
  • The delivery time and after-sales service offered by each manufacturer.
  • Whether or not a particular manufacturer offers warranty on its products or services (and what kind of warranty it is).

Place an order of fastener

  • You can contact us by email or phone.
  • You can also visit our factory.
  • You need to tell us the size and quantity of fasteners you need.
  • We will send you the quotation.
  • You need to pay a deposit.

Source: China Fasteners Supplier:

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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