Bolt vs Screw
Here is the short answer: a bolt is usually tightened by turning a nut, while a screw is driven directly into a material and held by its own threads. In practice the line gets blurry, and some fasteners carry both names. This guide breaks down the real differences so you can choose the right one.
What Is a Bolt?
A bolt is a fastener with an external thread and a head at one end. The bolt passes through a clearance hole in the parts being joined, and a nut is tightened onto the threaded end. The clamping force comes from the bolt being stretched between the head and the nut, which holds the joint tightly together. Hex bolts, carriage bolts, anchor bolts and U-bolts all belong to this family.
What Is a Screw?
A screw is a threaded fastener that is driven into the material itself. It either cuts or forms its own thread as it turns, or threads into a pre-tapped hole. There is usually no nut involved. The thread grips the surrounding material, which is what holds the parts together. Wood screws, machine screws and self-tapping screws are common examples.
Key Differences: Bolt vs Screw
| Feature | Bolt | Screw |
|---|---|---|
| How it holds | Nut pulls the joint tight | Thread grips the material |
| Needs a nut | Usually yes | Usually no |
| Driven by | Wrench or socket | Screwdriver, bit or drill |
| Typical use | High-load, serviceable joints | Wood, sheet metal, plastics |
| Pre-drilled hole | Clearance hole (larger than thread) | Pilot or pre-tapped hole |
| Removal | Easy to undo and reuse | May strip the hole if reused often |
When to Use a Bolt
Choose a bolt when the joint must carry a high load, when it needs to be assembled and disassembled repeatedly, or when you are joining metal parts and can fit a nut on the far side. Bolts are also the right choice for structural and lifting applications, where predictable clamping force matters. Our bolts and U-bolts are made for exactly these jobs.
When to Use a Screw
Choose a screw when you are fastening into wood, drywall, plastic or sheet metal, where a nut is not practical. Screws are faster to install, need access from only one side, and hold well in softer materials. For a full rundown of the options, see our types of screws guide.
Special Cases Worth Knowing
The naming is not always consistent:
- A lag screw (or lag bolt) has a hex head and a coarse thread, and it is driven with a wrench. It behaves like a bolt, but threads into wood like a screw.
- A machine screw threads into a tapped hole or nut, which makes it work like a small bolt.
- A shoulder bolt is a screw in shape but a bolt in function, with a smooth shoulder that acts as a bearing surface.
This is why it helps to think about how the fastener works rather than what it is called.
How to Choose
Ask yourself three questions:
- Can you reach both sides to fit a nut? If yes, a bolt is often stronger and more serviceable.
- What is the base material? Wood, plastic and thin metal usually want a screw.
- How much load and how often will it be removed? High load and frequent removal favor a bolt with a nut.
For flange and structural connections that need a threaded rod, stud bolts are the common choice.
FAQ
Is a bolt stronger than a screw?
Generally yes for the same diameter, because a bolt and nut clamp the joint with higher, more predictable tension. The exact strength depends on grade, material and size.
Can you use a bolt without a nut?
Not in the usual sense. A bolt without a nut is just a threaded rod; it is the nut that creates the clamping force.
What is a machine screw, a bolt or a screw?
A machine screw threads into a tapped hole or a nut, so it works like a small bolt even though it is called a screw.
Fasteners You Can Rely On
SolidLink manufactures bolts, screws, nuts, U-bolts and stud bolts in carbon steel, stainless steel and galvanized finishes, in standard sizes or made to your drawings. Browse our fasteners category or contact us for a quote.
