Screw vs bolt: Which do you need for your assembly project?

Whether assembling furniture or undertaking a DIY project, understanding the distinction between screws and bolts is crucial. After all, misusing these fasteners can lead to frustration and project delays. This guide provides a clear overview of their characteristics and appropriate applications.

What is a screw?

A screw is a metal fastener with a spirally grooved shaft (called a thread) running along most of its length. This design allows it to function in two ways:

1. Create its own thread: When screwed into a softer material like wood, the threads dig in and create a tight hold.

2. Fasten into a pre-threaded hole: In harder materials or when needing a stronger hold, the screw mates with a threaded hole, creating a secure connection.

To tighten or loosen the screw, you apply torque (twisting force) to the head. This head typically has a slot or recess designed to fit a specific screwdriver, like the familiar cross pattern of a Phillips screwdriver.

What is a bolt?

Similar to screws, bolts have external threads along their shaft. But unlike screws that create their own threads or screw into pre-drilled threaded holes, bolts are typically used with nuts.

A nut is a separate, donut-shaped piece with internal threads that match the bolt. Tightening the nut compresses the parts being joined, creating a secure ‘pressure sandwich’ between the bolt head, the parts, and the nut. 

Bolt vs screw: Which is better for your needs?

The popularity of self-assembly furniture has fueled the DIY movement. But if you can’t tell the difference between screws and bolts, your next project could become a frustrating fumble.

In the next section, we’ll explore the key distinctions between these common fasteners, empowering you to choose the right ones for any furniture assembly or disassembly project.

In terms of design simplicity

Screws are all about convenience. They thread directly into two pieces using a screwdriver, with some like wood screws even creating their own threads. This makes them perfect for quick projects, whether you have access to both sides or not.

Bolts, meanwhile, prioritize strength. They work with a nut on the opposite side, creating a powerful ‘clamping’ force. While tightening requires a nut and perhaps a wrench, the bolt-and-nut combo offers superior long-term stability for tougher jobs.

In terms of fastening strength

Screws are generally smaller and tend to be threaded along their entire length. This compact design minimizes damage by reducing the risk of splitting wood or cracking plastic, making them ideal for furniture assembly or projects involving softer materials.

Bolts are the muscle of the fastener world. They’re larger and often come with unthreaded sections (shanks) for extra strength. Unlike screws, they don’t thread directly into materials. Instead, they pass through pre-drilled holes and are secured with nuts, sometimes accompanied by washers for additional stability. This makes bolts perfect for heavy-duty projects like dining tables, sheds, and even roofs.

In terms of application range

Even in complex builds like large IKEA furniture, you’ll find nuts and self-tapping bolts and screws playing essential roles. As discussed earlier, their designs make them perfect for different situations.

Screws excel at securely joining smaller projects, regardless of the material (wood, plastic, or metal). However, bolts take centre stage for larger and heavier furniture due to their superior holding power. This explains why construction and cars rely heavily on bolts, while furniture and appliances primarily use screws.

In terms of load-bearing capacity

Bolts, with their sturdy design, are the preferred choice for securing structural elements in outdoor projects like roofs, sheds, and porches. Their strength also translates to applications like massive bridges handling significant weight.

Screws, however, are a valuable alternative for lighter-weight applications. They provide a reliable fastening solution for furniture such as cabinets, tables, and spice racks.

In terms of assembly convenience

Screws offer a clear advantage in terms of installation ease. They typically require just a screwdriver, making them a one-handed operation. Plus, you only need access to the front side of your project, as the screw creates its own threads as it’s driven in.

In contrast, bolts necessitate access to both sides of the project. Since they rely on a nut for fastening, you’ll need wrenches or another tool to tighten from the other side. This can introduce challenges in specific situations.

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