📌 Quick Answer
A bolt is an externally threaded fastener with a head, while a nut is a small block with an internal thread that screws onto the bolt.
Used together with a washer, the bolt passes through the parts and the nut tightens against them to clamp the joint.
🔹 Key Takeaways
- Bolt — external thread + head; nut — internal thread.
- They work as a pair to clamp parts together.
- A bolt mates with a nut; a screw threads directly into the part.
- Common nut types: hex, lock, wing, cap; common bolt types: hex, carriage, anchor.
Nut vs Bolt: The Key Difference
A bolt is a fastener with a head at one end and external (male) threads along its body. A nut is a square or hexagonal block with internal (female) threads that screws onto the bolt. The bolt and nut are used together to hold two or more parts firmly.
Comparison Table
| Parameter | Bolt | Nut |
|---|---|---|
| Thread | External (male) | Internal (female) |
| Shape | Cylindrical with a head | Hexagonal/square block |
| Function | Passes through the parts | Tightens onto the bolt |
| Used with | A nut (and washer) | A bolt |
How a Nut and Bolt Work Together
The bolt is inserted through aligned holes in the parts to be joined. A washer is usually placed under the nut to spread the load, and the nut is screwed onto the bolt’s threads and tightened. This creates a strong clamping force that holds the parts together yet can be undone for maintenance.
Types of Nuts and Bolts
- Bolts: hex bolt, carriage bolt, anchor bolt, eye bolt, U-bolt.
- Nuts: hex nut, lock nut, wing nut, cap nut, flange nut.
Frequently Asked Questions
What is the difference between a nut and a bolt?
A bolt has external threads and a head; a nut has internal threads and screws onto the bolt to clamp parts together.
Can a bolt be used without a nut?
A bolt is normally used with a nut, but it can thread directly into a tapped hole; when it does, it functions like a screw.
What is the difference between a bolt and a screw?
A bolt is tightened by turning a nut, whereas a screw forms or fits its own thread in the material and is turned by its head.
Why is a washer used with a nut and bolt?
A washer distributes the clamping load over a larger area, protects the surface and helps prevent the nut from loosening.