Screws vs. Bolts vs. Nuts: How to Tell Them Apart
Screws, bolts, and nuts are the most common fasteners in daily life and industry. They look similar, but each has a distinct appearance, function, and application. Mixing them up can lead to weak joints, damaged parts, or even safety hazards. This guide helps you quickly distinguish between screws, bolts, and nuts — once and for all.
1. Differences in Appearance
The most obvious difference is how they look.
Screw
Front end: Pointed or tapered tip.
Thread: Typically runs along the entire body or most of it. Often has a larger pitch (wider spacing between threads).
Head: Many types exist — flat head, pan head, round head, countersunk, etc. The head usually has a drive recess (Phillips, slotted, hex, Torx, etc.).
Key visual clue: A screw can be driven directly into a material without a pre-formed mating thread or nut.
Bolt
Structure: A cylindrical threaded fastener designed to be used with a nut.
Head shapes: Hexagonal head (most common), round head, square head, countersunk head, etc.
Key visual clue: A bolt has a blunt end (not pointed) and is usually partially threaded (a plain shank under the head is common). It requires a nut to fasten.
Nut
Structure: A flat, hollow, polyhedral (typically hexagonal) cylinder with an internal thread.
Key visual clue: A nut has no head — it is a standalone threaded block that mates with an external thread (bolt or screw). Most common shape: hex nut.
2. Differences in Function
How they work is fundamentally different.
Screw
A screw uses the physical principles of inclined plane (thread) and friction to gradually tighten itself into a material.
• It creates its own mating thread (in wood, plastic, thin metal) or mates with a pre-formed internal thread.
• Does not require a nut to work (though some screws can be used with nuts).
Bolt
A bolt is a cylindrical threaded fastener that must be used with a nut.
• Together with a nut, it securely fastens two or more parts that have clearance holes (through holes).
• The bolt is inserted through the holes, and the nut is screwed onto the other end to clamp the assembly.
Nut
A nut is a tightening component.
• It provides the internal thread that mates with a bolt (or a threaded screw).
• When you turn the nut (or the bolt), the threads engage, creating tension and clamping force.
3. Differences in Applications
Each fastener excels in specific areas.
Screw Applications
Screws are essential in daily life, from tiny precision devices to large structures.
| Size Category | Examples |
| Micro screws | Cameras, glasses, watches, electronics (smartphones, laptops) |
| General screws | TVs, electrical appliances, musical instruments, furniture, toys |
| Large screws | Engineering, construction, bridges (heavy structural screws) |
| Transportation | Airplanes, trams, cars, trains — both large and small screws |
Bolt Applications
Bolts are often called the "rice of industry" because they are so widely used.
• Electronic products
• Mechanical products
• Digital devices
• Power equipment
• Electromechanical products
• Automotive and heavy machinery
Wherever two parts need to be clamped together with a nut, a bolt is the solution.
Nut Applications
Nuts are paired with bolts. Major industries include:
Automotive – cars, trucks, buses
Compressors
Construction machinery
Wind power generation equipment
Agricultural machinery
Fastener industry (nuts, bolts, washers)
Casting industry
Drilling equipment
Nuts are also used in almost every bolted joint — from furniture assembly to skyscrapers.
Quick Comparison Table
| Feature | Screw | Bolt | Nut |
| Appearance | Pointed tip, full or partial threads | Blunt end, usually hex head, partial thread | Hexagonal block with internal thread |
| Works with nut? | No (usually self-tapping or wood screw) | Yes, must be used with a nut | Yes, must be used with a bolt |
| Typical thread type | External thread (self-tapping or machine) | External thread (machine thread) | Internal thread |
| Installation | Driven directly into material | Inserted through holes, nut tightened on other side | Screwed onto bolt |
| Common materials fastened | Wood, plastic, thin metal, sheet metal | Metal parts, structural components | Same as bolt |
| Removable? | Yes (with screwdriver/drill) | Yes (with wrench) | Yes (with wrench) |
Common Misconceptions Clarified
❌ "A bolt can be used without a nut if it goes into a threaded hole."
✅ That part becomes a "screw" by function. Many fasteners blur the line. The engineering distinction: a bolt is designed for a nut; a screw is designed to mate with an internal thread in the workpiece (or create its own).
❌ "All pointed fasteners are screws."
✅ Mostly true, but some "self-drilling screws" look like bolts? No — bolts are not pointed.
❌ "Nuts are only for bolts."
✅ Yes — but some nuts also work with threaded rods (which are essentially long bolts without a head).
Final Takeaway
Screw = pointed tip, drives directly into material, no nut needed.
Bolt = blunt end, works with a nut to clamp parts with through holes.
Nut = hexagonal block with internal threads, mates with a bolt.
Choose the right fastener for the job. When in doubt: if it goes into wood or plastic without a nut → screw. If it goes through a hole and needs a nut on the other side → bolt + nut.