Nuts and bolts are common fasteners in the manufacturing industry, serving the purpose of mechanically connecting two or more components together. For instance, when installing equipment, screws are used to secure various objects. Many people are not clear about the differences between bolts and nuts. Some believe that bolts are nuts, and nuts are bolts. However, this misconception is incorrect. In this CNC machining guide, we will delve into the distinctions between bolts and nuts, as well as the types they come in.
What is a Nut?
A nut is a fastening device, typically made of metal, featuring a square or hexagonal block with a central hole that has internal threads. These threads fit onto the male threads of a corresponding bolt or screw, creating a secure connection. Nuts are essential in fastening machine and structural components. Variations include standard square and hexagonal nuts, as well as specialized types like slotted nuts and locknuts that prevent loosening.
Advantages and Disadvantages of Nuts
| Advantages | Disadvantages |
|---|---|
| Provides strong and secure fastening | Requires proper torque to avoid loosening |
| Can be reused multiple times | Threads can wear out or become damaged over time |
| Available in various sizes and materials | Some types may require specific tools for installation |
| Generally easy to install and remove | May loosen under vibration or dynamic loads |
| Relatively inexpensive | Can incur additional costs if specialized nuts are needed |
| Easy to inspect and maintain | May need periodic tightening |
| Distributes load evenly across threads | Improper installation can lead to uneven load distribution |
| Easily available in hardware stores | Small sizes can be difficult to handle |
Types of Nut
There is a wide variety of nut types, each with its specific uses and advantages. Some of the most common types of nuts include:
1.Acorn Nuts
Acorn nuts, as the name suggests, are nuts with caps, named for the acorn-shaped cap at the top. Their primary purpose is to prevent foreign particles and moisture from infiltrating the interior, thus avoiding corrosion and rust. They also serve to minimize the risk of skin and clothing catching on sharp edges. Therefore, these nuts are often used in industrial machinery in areas where contact with the human body is frequent, reducing the risk of injury to personnel.
2.Weld Nuts
Weld nuts are nuts designed to be welded onto another component. They are typically made of weldable materials and have a thicker structure to accommodate the welding process. Weld nuts create a strong connection by fusing the two separate pieces into one solid unit through high temperatures.
Weld nuts find widespread use in applications requiring high-strength connections, such as in construction, bridges, vehicle manufacturing, and other fields. They are welded into place to provide sturdy support and connection at their respective positions.
3.Hex Nuts
Hex nuts are named for their hexagonal shape, featuring six equal sides and angles. This design allows them to be easily tightened or loosened using tools such as wrenches or screwdrivers. Hex nuts are suitable for fastening most mechanical components and equipment, capable of withstanding high pressures without deformation or damage.
4.Wing Nuts
Wing nuts feature a wing-shaped structure with wings on each side of the nut, allowing them to be easily rotated by hand without the need for tools. This makes them particularly suitable for use on equipment that requires frequent disassembly or fastening. Their design enables quick and convenient operation.
Wing nuts are commonly used in mechanical equipment, electrical equipment, transportation vehicles, and other applications where frequent tightening or loosening of nuts is necessary. They are the perfect solution for situations requiring frequent adjustment or removal of nuts.
5.Barrel Nuts
Barrel nuts, also known as sex bolts or Chicago screws, are made of steel and feature extremely thin bolt heads and metal parts. Their advantage lies in not requiring flanges to be machined or forged on the receiving component, thus reducing their weight.
6.Jam Nuts
Jam nuts are highly practical fasteners, typically hexagonal in shape and half the size of regular nuts. They come in various designs and structures, including but not limited to friction locking, mechanical locking, rivet locking, and structural locking methods.
In mechanical and engineering applications, the problem of nuts loosening due to vibration or impact is often encountered. The introduction of jam nuts effectively addresses this issue. For example, In automotive fasteners, jam nuts are primarily used as fasteners for critical components such as automotive suspension, engines, and transmissions to prevent loosening caused by vibration and impact.
7.Lock Nuts
Lock nuts utilize friction between the nut and bolt to self-lock, ensuring the stability of the connection. In some critical applications, additional anti-loosening measures may be taken to ensure the reliability of nut locking. Refer to the “jam nuts” mentioned above.
Lock nuts are widely used in industries such as machinery to secure threaded pipe fittings or other components, ensuring stable and safe connections.
8.Flange Nuts
Flange nuts, also known as flanged nuts, washer-faced nuts, serrated flange nuts, or hex flange nuts, feature a wide flange at one end, which effectively acts as an integrated washer. When the nut is tightened, this flange distributes pressure evenly across the secured component, reducing the risk of damage due to excessive pressure and increasing the stability of the entire connection.
Please watch the following YouTube video to learn how your nuts and bolts are made.
What is a Bolts?
A bolt is a mechanical fastener typically used with a nut to connect two or more parts. It consists of a head and a cylindrical body with screw threads along part of its length. Bolted joints can be easily disassembled and reassembled, making bolts a preferred choice in mass-produced items and steel structures. Washers are often used alongside bolts to prevent loosening and distribute pressure.
Advantages and Disadvantages of Bolt
| Advantages | Disadvantages |
|---|---|
| Provides strong and secure fastening for heavy loads | Requires precise torque to avoid over-tightening or loosening |
| Can be reused multiple times with proper maintenance | Threads can wear out or become damaged over time |
| Available in various sizes, materials, and grades | Some applications may require specific types or grades |
| Generally easy to install and remove with basic tools | May require multiple components (nuts, washers) |
| Relatively inexpensive for standard bolts | High-strength or specialized bolts can be costly |
| Easy to inspect and maintain | May need periodic re-tightening, especially under vibration |
| Distributes load evenly across the bolted joint | Improper installation can lead to uneven load distribution |
| Widely available in hardware stores and suppliers | Can be time-consuming to install in large quantities |
Types of Bolts
There are various types of bolts that can be classified according to different standards and requirements. The following are some common types of bolts:
1.Anchor Bolts
Anchor bolts are commonly used in the construction industry. They utilize the structure of the bolt itself, combined with special components, to expand and anchor in concrete foundations within bolt holes. This type of bolt is convenient to install on-site and can immediately bear loads once installed. Moreover, they can be disassembled and reused if necessary, making them popular among professionals and DIY enthusiasts alike.
2.Carriage Bolts
Carriage bolts consist of a head and a cylindrical shaft with external threads, making them fasteners that require use with nuts to securely connect two components with through-holes. Their heads are often hexagonal and relatively large, with a rounded shape and no designs such as cross-slots or internal hexagons. This design not only facilitates installation but also serves as a deterrent against theft during the connection process.
3.Blind Bolts
Blind bolts are a special type of bolt characterized by their non-through-hole design. They typically feature internal hexagon and internal hexagon with grip slot structures, facilitating installation using hexagon wrenches or socket heads. This design makes blind bolts particularly useful in situations where tightening can only be done from one side.
Blind bolts exhibit high strength. For example, a blind bolt with an M20 specification can have a shear load-carrying capacity design value of up to 54.5 kN (single shear surface), and the tensile load-carrying capacity design value varies depending on the type of blind bolt but generally remains high. This strength ensures that blind bolts can provide stable and reliable connections in various applications.
4.U-Bolts
U-bolts, also known as horse bolts, are named for their unique U-shaped structure. These bolts are non-standard components. They feature threads at both ends of the U shape, which can be combined with nuts to achieve fastening. U-bolts are primarily used for securing cylindrical objects such as pipes or flat objects like vehicle leaf springs.
5.Eye Bolts
Eye bolt is a type of bolt with a lifting eye on the head, characterized by a longer shaft and fewer threads. It consists of three parts: the lifting eye, nut, and bolt. Usually used for lifting or hanging heavy objects, such as outdoor fences, tower cranes, and other scenarios.
During installation, the lifting eye bolts must be installed vertically on the plane of the workpiece, the joint surface should be flat and tight, and adjusted to the stretching direction to avoid contact with sharp edges. Its test load is 2.5 times the working load, and 20000 fatigue tests are conducted at 1.5 times the working load.
6.Hex Bolts
Hex bolts are one of the most commonly used types of bolts. Their surfaces are hexagonal in shape, allowing for rotation using tools such as wrenches to apply the necessary force for fastening. Regarding the threaded portion, hex bolts can be fully threaded or partially threaded. They are suitable for connecting various mechanical equipment and structures.
7.Flange Bolts
Flange bolts primarily consist of three parts: a hexagonal head, a flange (which includes a washer and is integrated with the hexagon below), and a shaft (a cylindrical body with external threads). The flange serves as a washer, distributing the load and providing a larger “support area to stress area ratio” for the bolt.
The working principle of flange bolts mainly relies on the mutual engagement of the threads. When the nut is rotated, the threads between the bolt and the nut interlock, causing the bolt to move forward or backward, achieving the fastening effect. Compared to regular bolts, flange bolts have wider heads and usually have expanded tails, making them more sturdy and secure.
Flange bolts are widely used in scenarios requiring the bearing of heavy loads and higher safety, such as automotive engines and heavy machinery products.
How to Choose the Appropriate Nut for Your Bolt?
Selecting the appropriate nut for a bolt is a process that requires considering multiple factors. Below are some key steps and factors to consider:
1.Match Thread Specifications
Ensure that the chosen nut’s thread specifications match those of the bolt completely. This includes parameters such as nominal diameter, pitch, and thread count. For example, an M6 bolt should correspond to an M6 nut. If the specifications don’t match, the nut won’t properly install on the bolt, affecting the fastening effect.
For more thread specifications and sizes, please refer to the following article: Thread Size Chart
2.Size and Shape
Choose the appropriate nut size and shape based on the usage scenario and requirements. For instance, the selection of head type may involve factors such as anti-tamper performance, appearance, and stability. If a stable and secure nut is needed, consider using a prevailing torque nut or a nut with washers.
3.Determine Required Strength
Select the nut material and grade based on the strength requirements of the application. For instance, for applications requiring high loads, opt for high-strength nuts.
4.Consider Environmental Conditions
If the nut will be used in damp, corrosive, or high-temperature environments, choose a nut with corresponding corrosion resistance and high-temperature characteristics. Stainless steel nuts are typically suitable for these special environments.
5.Choose the Appropriate Nut Type
Select the appropriate nut type based on specific needs. For instance, if better anti-tamper performance is required, consider using a hex flange nut; if higher strength is needed, opt for a prevailing torque nut, etc.
Common Bolt and Nut Materials
The commonly used materials for bolts and nuts include:
- Carbon steel
- Stainless steel
- Alloy steel
- Aluminum alloy
- Titanium alloy
- Brass
- Polymers, such as nylon
What is the Difference Between Nuts and Bolts?
A bolt consists of a head and a cylindrical body with screw threads along part of its length. It is typically used with a nut, which is the female counterpart with internal threads that match the bolt’s threads. Washers are often added between the bolt head or nut and the surfaces they connect to prevent loosening and distribute pressure evenly.
Nut vs bolt chart
| Feature | Nut | Bolt |
|---|---|---|
| Purpose | Provides the opposite side of the threaded hole to secure the bolt to the component | Passes through the component and engages with a nut to form the connection |
| Shape | Typically hexagonal or square | Mostly cylindrical |
| Structure | Hollow | Solid |
| Function | Provides the threaded hole for the bolt to be screwed into | Provides torque to screw into the nut |
| Material | Usually metal | Usually metal |
| Fastening method | Matches with the bolt by rotation | Matches with the nut by rotation |
| Size | Size usually determined by thread specifications | Size usually determined by diameter and length |
| Primary role | Provides threaded hole allowing bolt fixation | Provides torque and force for a secure connection |
| Common types | Standard, hexagonal, square | Flat head, round head, screw type, stud type |
How Are Nuts And Bolts Held Together?
Nuts and bolts are held together primarily through threaded engagement. The external threads on the bolt mesh with the internal threads of the nut, creating a tight connection that resists pulling apart. As the nut is tightened, it applies compressive force, squeezing the parts together. Friction between the threads helps prevent loosening, while the slight stretching of the bolt under tension further enhances the clamping force. In applications prone to vibration or movement, additional locking mechanisms like nylon-insert lock nuts or mechanical washers are used to maintain tightness and prevent unintended loosening over time.
Strength Comparison: Nut vs. Bolt
In engineering, the strength of a joint between a nut and a bolt is crucially important. When assembling a joint, torque is applied to achieve a proper clamp load, ensuring the components are securely fastened. If too much torque is applied:
- Bolt Strength: If the bolt is weaker, it may stretch or even break before reaching the intended torque, signaling a problem during assembly.
- Nut or Tapped Hole Strength: If the nut or tapped hole is weaker, it may yield or fail under excessive torque, leading to thread damage like galling or seizing. This can compromise the joint’s integrity and potentially lead to failure under service loads.
To ensure a reliable joint, it is recommended that the nut (or the threaded member) be stronger than the bolt.
Difference Between Bolts, Nuts, Screws, and Rivets
| Aspect | Bolts | Nuts | Screws | Rivets |
|---|---|---|---|---|
| Function | Used to join two or more components together | Secures and tightens bolts | Used to fasten materials by turning | Joins materials by permanent deformation |
| Mechanism | External threaded shaft | Internal threaded hole | External threaded shaft into a threaded hole | Deforms to secure materials without threads |
| Usage | Requires access to both sides of the material | Requires only one side for installation | Used where disassembly may be required | Used in applications needing permanent fastening |
| Installation | Inserted through aligned holes, secured with nuts | Screwed onto bolts to secure components | Driven into materials by rotating | Requires special tools for installation |
| Disassembly | Easily disassembled and reassembled | Easily removed with access to the nut | Can be unscrewed for maintenance | Typically irreversible once set |
| Types | Hex bolts, carriage bolts, eye bolts, etc. | Hex nuts, lock nuts, wing nuts, etc. | Wood screws, machine screws, self-tapping screws | Blind rivets, solid rivets, pop rivets |
| Strength | Provides strong, reliable mechanical fastening | Enhances clamping force of bolts | Holds materials firmly under tension | Offers high shear and tensile strength |
| Applications | Structural assemblies, machinery | Automotive, construction, general hardware | Woodworking, metalworking, electronics | Aerospace, automotive, structural building |
For more information about rivets, please read this article: What is a Rivet
Why Use Washers With Nuts and Bolts?
Using washers with nuts and bolts ensures even distribution of load across the fastened surfaces, protecting them from damage and preventing loosening over time. Washers also help create a secure clamping force, enhancing the integrity of the connection by spreading the load over a larger area. In specific cases, washers may be placed on the bolt side to facilitate installation or removal.
Summary
In summary, nuts and bolts have their own characteristics in function, structure, and use, and they work together to achieve the fastening of mechanical connectors. In practical applications, it is necessary to select appropriate types, specifications, and materials of nuts and bolts based on specific connection requirements and environmental conditions.
Boyi, as a professional provider of CNC machining services, possesses advanced equipment and a skilled team capable of delivering high-quality, high-precision fasteners to customers. Feel free to contact Boyi anytime for detailed consultations and expert advice.
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FAQ
The bolt might be stronger than the nut, especially if it’s made from a higher grade or stronger material. However, in a properly designed and assembled fastening system, both the nut and the bolt should be appropriately matched in strength to ensure the overall integrity of the joint.
Torque bolts instead of nuts for better control and consistency in tightening, ensuring uniform clamping force and reducing the risk of over-tightening or stripping threads.
Bolts are typically used for heavy-duty applications where high strength and load-bearing capacity are needed. Screws are often used for lighter-duty applications or where the joint needs to be disassembled more frequently.
A bolt without a nut is often referred to as a screw. While bolts typically require a nut to secure objects together, screws are designed to be threaded directly into a material, creating their own internal thread.
In terms of strength, bolts are generally stronger than nuts. Bolts are designed to handle significant loads and stresses, particularly when used in conjunction with nuts to create secure connections.
A nut is a small, threaded metal block, usually hexagonal, while a bolt has a head and a threaded shaft. The nut fits onto the bolt’s threads to secure materials together.
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
