Bolts vs. screws: What’s the difference and when to use each
Bolts and screws are both fastening devices with their own characteristics. When to use bolts vs. screws comes down to your application. Understanding their similarities and differences will help you easily determine which you should use and when. To that end, we’ve put together this guide to help you, but if you still have questions, our expert team is happy to help. Here, we cover:
Brief comparison of bolts and screws
Bolts and screws play essential roles as fastening devices, yet they possess distinct attributes that set them apart in terms of design, function, and application. There are different types of bolts and screws, of course, but all share fundamentals.
View our range of screws and bolts
Design and Function
Bolts: Bolts are designed to work with a nut and two washers. This is why a bolt will be longer than the width of the material being fastened. The bolt needs to protrude through the other side in order to screw into the nut. Bolts possess a threaded shaft with a smooth or unthreaded segment, called the shank.
When paired with a nut and washers, they generate a clamping force by distributing the load across the washer’s face and material when the nut is threaded on. This helps secure the connection over a larger surface area and helps prevent the bolt and nut from damaging the material or possible pull through.
Installing a bolt requires a handheld or pneumatic wrenches to install into a pilot hole. Some common types include the carriage bolt, lag bolt and hex bolts.
You can learn more in our guide, What are the Different Types of Nuts and Bolts?
Screws: Screws typically feature threads along their entire length. They’re either inserted directly into a tapped hole, or threaded hole, or they can create their own threads as they’re screwed in. These are called self-tapping screws. Common types include machine, drywall, wood, and sheet metal screws. Machine screws are designed to be screwed into a pre tapped hole, where the drywall, wood, and sheet metal screws are designed to be screwed into pilot holes where the threads can cut into the material to create their own threads.
Learn more in our guide, What are Screw Heads, Drives and Threads?
Head Types:
Bolts: Bolts typically have a flat or slightly rounded head with various shapes, such as square, slotted, and hexagonal, to accommodate wrenches or sockets.
Screws: Screws are available in a wide range of head types and drives such as Phillips and Torx. Each head shape serves a purpose.
Applications:
Bolts: Bolts are commonly used for one of two reasons: 1) Where disassembly might be necessary or 2) Where a secure and adjustable connection is needed. Bolts are typically used in construction, automotive, and machinery.
Screws: Screws fasten components and join materials such as wood, metal, and plastic. They are versatile and used in everyday items like furniture, electronics, and appliances, and industrial applications such as automotive and machinery.
While both bolts and screws share the fundamental purpose of fastening objects, bolts rely on a separate nut for their operation and excel in scenarios that require adjustability and disassembly. In contrast, screws establish their threads within the material they penetrate and provide a secure and self-contained fastening solution. Let’s compare specific screw types to bolts.
Set screws vs. bolts
Set screws, seen here, are typically smaller and feature a flat or pointed tip, designed to secure one component within or against another by directly engaging with the surface. They’re often used in situations where a flush or hidden fastening is needed, such as in machinery or electronics. In contrast, bolts are larger and clamp two or more components together. This particular set screw has a hex socket, while bolts often have hex-shaped heads.
You can learn more in our guide, What is a Set Screw?
Machine screws vs. bolts
There are many different types of machine screws, such as this nylon cheese head screw. Machine screws are typically smaller, uniform in diameter, and have a threaded shaft along their entire length. They’re primarily used to fasten metal components together, often by threading into pre-tapped holes. Bolts, on the other hand, are larger, have a shank that may be partially unthreaded, and are paired with a separate nut to create a clamping force.
You can learn more in our Guide to Machine Screws.
Cap screws vs. bolts
Cap screws typically have a threaded shaft with a cylindrical or hexagonal head. This example of a socket head cap screw has a cylindrical head with a hex socket. Cap screws typically have a threaded shaft, allowing for precise torque application. The head size distributes torque more effectively, reducing the risk of stripping or damaging the fastener during tightening or removal.
When to use bolts and when to use screws based on application
Bolts vs. screws. The choice between using one or the other in a particular application depends on several factors. These include structural requirements, materials being joined, load-bearing capacity, ease of assembly, and the need for disassembly.
Here are some general guidelines to help you decide when to use bolts and when to use screws:
Use bolts for:
- High load-bearing requirements: Typically used in applications where there’s a significant load or stress that needs to be supported. They’re ideal for situations where strength and stability are paramount.
Applications: Construction, oil & gas pipes, heavy machinery
- Adjustability: Easy adjustability since they’re used in combination with nuts. If you need to fine-tune the tension or alignment of parts, bolts are a better choice.
Applications: Automotive suspension systems, conveyor systems
- Disassembly and maintenance: Suitable for applications where disassembly for maintenance, repair, or future modifications is necessary. You can simply remove the nut to disassemble the components.
Applications: Solar panels, construction equipment, manufacturing machinery
Find out more in our Guide to Bolt Grades and Applications
Use screws for:
- Fastening into threads: Machine screws thread into pre tapped holes of compatible thread size. Self-tapping screws are designed to cut their own threads in a pre-drilled, untapped hole.
Applications: electronics assembly, automotive manufacturing, woodworking
- Convenience and speed: Faster and easier to install since they don't require a separate nut. This makes them suitable for applications where efficiency matters.
Applications: Assembly line manufacturing, sheet metal fabrication
- Smaller or lighter loads/non-structural applications: Screws don’t require nuts and are suitable for lighter load-bearing applications where the load is not significant, such as securing small components, fastening electronics, or assembling furniture.
Applications: Consumer appliances, electronic devices, furniture assembly
- Materials with low shear strength: Suitable for materials with lower shear strength, such as plastic or particleboard, where they can create strong connections.
Applications: Plastic enclosures, cabinetry, furniture
Advantages and disadvantages of using screws or bolts
Screws and bolts each have their own pros and cons.
Screws: advantages
- Easy to install: Straightforward to use – simply install with screwdrivers or power drills.
- Adjustable: You can make adjustments after installation, which is useful when alignment or positioning needs to change.
- Easy to remove: Simple to remove without damaging materials.
- Wide material compatibility: Can be used with various materials, including wood, plastic, metal, and composites.
Screws: disadvantages
- Lower load capacity: Unsuitable for heavy-duty or high-stress applications.
- Less clamping force: Lack of a nut means less clamping force than bolts.
Bolts: advantages
- High load capacity: Can handle heavy loads and provide significant clamping force – perfect for structural and heavy-duty applications.
- Secure fastening: Provides a robust and secure connection.
- Versatile: Bolts can be used in a wide range of materials and applications, including structural, automotive, and industrial settings.
Bolts: disadvantages
- Complexity: Bolts involve more components (bolt, nut, and sometimes washers), which can complicate installation and maintenance compared to screws.
- Slower installation: Bolts generally take longer to install due to the need for a separate nut and, potentially, two tools (one for the bolt and one for the nut).
- Difficult to install in tight spaces: If space is limited, you’ll need to give special attention to how you’ll access bolts.
You might also find it helpful to read How to Measure Bolt Size.
Considerations for choosing between bolts and screws
The choice between bolts and screws hinges on several critical factors. Load-bearing requirements play a pivotal role, with bolts being the preferred choice for high-load and structural applications due to their superior clamping force and strength. When paired with nuts and washers, bolts reduce stress concentrations, which is important in applications where uniform force distribution is crucial.
Screws are more suitable for lighter loads and non-structural tasks. Material compatibility is another crucial consideration; screws excel with materials like plastic or wood due to their ability to create strong connections. Accessibility and space constraints also come into play, with screws being more practical in confined spaces. Adjustability and ease of disassembly make screws ideal for applications requiring fine-tuning or future maintenance, while bolts can be adjusted but may require more effort.
The fastener you use should align with the specific needs of your application, balancing load-bearing capacity, material compatibility, access constraints, and required adjustability.
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If you’re not quite sure which solution will work best for your application, our experts are always happy to advise you.
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Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.