Nuts vs Bolts: Key Differences

author: YITECH

2025-10-24

Discover the difference: bolts provide external threading for fastening, while nuts offer internal threading to secure the connection in machinery and construction. Essential components.

Table of Contents

1. What Are Nuts and Bolts?

Nuts and bolts are fasteners—tools used to join two or more components together. They are typically used in combination, but each serves a distinct function.

What is a bolt?

A bolt is generally a long, cylindrical metal piece consisting of two main parts:

Head (at one end): Commonly hexagonal, though round or flat designs are also available. The head prevents the bolt from passing completely through the components being joined.
External threads (along the shaft): These are spiral grooves running along the body of the bolt. The threads allow the bolt to engage with a nut.

Bolts are usually made from materials such as steel, brass, or stainless steel, and come in various lengths and diameters (referred to as "sizes") to suit different applications.

What is a nut?

A nut is typically a small, hexagonal metal block with one key feature:

Internal threads (inside the nut): These spiral grooves match the external threads of a bolt. When the nut is twisted onto the bolt, the threads interlock securely.

Nuts can be made from steel, brass, plastic, or other materials, and their size must correspond to that of the bolt—for example, an M8 bolt requires an M8 nut.

2. Key Differences Between Nuts and Bolts

Nuts and bolts need to be used in combination, but they differ significantly in four aspects:

Thread Type

Bolts have external threads (spiral grooves on the outside), while nuts have internal threads (spiral grooves on the inside). This is the most obvious difference—the threads on a bolt protrude outward, whereas the threads in a nut are recessed inside.

Core Function

Bolts act as the "connecting rod," passing through holes in the components to be joined. Nuts serve as the "lock," screwing onto the bolt to clamp the parts together securely.

Installation Method

During installation, the bolt is first passed through the holes in the components, and then the nut is screwed onto its threads. For tightening, you can either hold the bolt head (with a wrench) and turn the nut, or hold the nut and turn the bolt head.
Without a nut (or a threaded hole), a bolt cannot complete the installation. Similarly, without a bolt (or another threaded fastener), a nut cannot be used.

Ability to Function Independently

Neither can work alone: a bolt without a nut will simply fall out of the components it passes through, and a nut without a bolt has nothing to grip onto—making it impossible to fasten anything.

3. Nuts vs. Bolts: Detailed Comparison Table

Feature	Nuts	Bolts
Thread Type	Internal (inside the nut)	External (on the bolt's body)
Main Structure	Small, often hexagonal; hollow center	Long, cylindrical; has a head at one end
Core Function	Locks parts in place; creates clamping force	Passes through parts; provides a thread for the nut
Installation Tool	Wrench (to turn the nut)	Wrench or screwdriver (to turn the head)
Common Materials	Steel, brass, stainless steel, plastic	Steel, brass, stainless steel, titanium
Can Be Used Alone?	No	No
Size Matching	Must match bolt size (e.g., M6 nut for M6 bolt)	Must match nut size or threaded hole size
Typical Applications	Securing bolts in furniture, cars, machinery	Joining wood, metal, or plastic parts in buildings, appliances

4. How Nuts and Bolts Work Together

Nuts and bolts create a strong joint by using clamping force. Here's the step-by-step process:

Drill holes through the parts you want to join. The holes must be slightly smaller than the bolt's unthreaded part (so the bolt fits tightly).
Push the bolt through the holes. The bolt's head should sit against one side of the parts.
Twist the nut onto the bolt's threaded end (the end sticking out of the parts).
Tighten the nut with a wrench. As you turn the nut, it moves along the bolt's threads. This pulls the bolt's head and the nut closer together.
The tightness creates clamping force. This force presses the parts against each other—so they don't move apart.

The amount of tightness (called torque) matters. Too loose, and the parts can wiggle. Too tight, and you might strip the threads (ruin the grooves) or break the bolt.

5. Common Types of Nuts (Including Brass & Rivet Nuts)

Nuts come in many types, each for specific jobs. Two important types are brass nuts and rivet nuts—we covered these in our earlier blogs.

**1. Brass Nuts (From What are the categories of brass nuts according to their use?)**

As we explained in that blog, brass nuts are split into types based on their use:

Decorative Brass Nuts: Shiny and corrosion-resistant. Used for furniture, light fixtures, or decorative hardware. They add a classic look.
Plumbing Brass Nuts: Designed for water pipes (like sink or shower connections). They resist rust from water better than steel nuts.
Electrical Brass Nuts: Used in electrical boxes or wire connections. Brass conducts electricity a little—so these nuts keep electrical parts secure without causing shorts.

**2. Rivet Nuts (From Rivet Nuts)**

Rivet nuts are special. They’re different from regular nuts because they're made for thin materials (like sheet metal or plastic). Regular nuts need a bolt to pass through and a way to hold the nut from the back. Rivet nuts don't—you “set” them into the thin material first.For example: If you want to fasten a part to a thin metal sheet, you can't use a regular nut (there's no space behind the sheet). Instead, you insert a rivet nut into a hole in the sheet, squeeze it to lock it in place, then twist a bolt into the rivet nut.Rivet nuts are used in cars, airplanes, and electronics—places where thin materials need strong fasteners.

3. Other Common Nut Types

Hex Nuts: The most common type. Hexagonal shape makes them easy to grip with a wrench.
Lock Nuts: Have a special design (like a nylon ring inside) to stop them from coming loose. Used in cars or machinery that vibrate a lot.
Wing Nuts: Have two “wings” (flat parts) so you can twist them by hand (no wrench needed). Used for parts you need to remove often (like a toolbox lid).

6. Expert Opinion on Nuts and Bolts

Dr. Sarah Miller is a mechanical engineer with 18 years of experience in fastener design. She says: “Nuts and bolts are the most basic but important fasteners. People often overlook how well they need to work together. For example, if you use a brass nut (as in your brass nut blog) with a steel bolt, that’s fine—brass resists rust, so it’s good for outdoor use. But if you mix sizes (like an M8 nut with an M10 bolt), the threads won’t match, and the joint will fail.

She adds: “Torque is another big thing. Most people tighten nuts and bolts too hard or too soft. You need to use a torque wrench to get the right tightness. Also, rivet nuts (from your rivet nut blog) are a game-changer for thin materials—they let you make strong joints where regular nuts can’t work. The key is choosing the right nut and bolt for the job.”

7. FAQ About Nuts and Bolts

Q1: Can a nut be used without a bolt?

A: No. Nuts have internal threads that need to grip external threads (from a bolt, screw, or threaded rod). Without something with external threads, a nut can't hold parts together.

Q2: What's the difference between a bolt and a screw?

A: A bolt needs a nut to fasten parts. A screw has threads that grip directly into a threaded hole (no nut needed). For example: A screw goes into a wooden board's threaded hole. A bolt goes through two boards and needs a nut.

Q3: Why use brass nuts instead of steel nuts?

A: Brass nuts resist rust better than steel nuts. They also don't react with other metals (like aluminum) as much. As we said in What are the categories of brass nuts according to their use?, brass nuts are great for outdoor, plumbing, or decorative jobs.

Q4: What are rivet nuts used for?

A: As we covered in Rivet Nuts, rivet nuts are for thin materials (like sheet metal) where regular nuts can't be used (no space behind the material). They lock into the thin material, then a bolt twists into them. Used in cars, planes, and electronics.

Q5: How do I choose the right size nut for a bolt?

A: Match the nut's size to the bolt's size. Bolt sizes are marked (e.g., M6, 1/4-inch). An M6 bolt needs an M6 nut. You can also check the thread count (how many threads per inch) to be sure—matching thread count ensures a tight fit.

Q6: What happens if I over-tighten a nut and bolt?

A: Over-tightening can strip the threads (ruin the grooves) on the nut or bolt. It can also break the bolt or warp the parts you're joining. Always use a torque wrench to follow the recommended tightness.

Q7: Are brass nuts compatible with steel bolts?

A: Yes. Brass and steel work well together. Brass nuts resist rust, so they're a good match for steel bolts in wet or outdoor areas. Just make sure the sizes and thread counts match.

Q8: Can I reuse nuts and bolts?

A: It depends. If they're in good shape (no stripped threads, no rust), you can reuse them. But lock nuts (with nylon rings) should be replaced after use—their nylon ring wears out and won't lock well again. Rivet nuts can't be reused once they're set into a material.

DongGuan YiTai Electronic Technologies Co.,Ltd

DongGuan YiTai Electronic Technologies Co.,Ltd is a manufacturing service provider located in Dongguan, China.

YiTai specialized in CNC turning machining and sheet metal fabrication mainly. As a member of Hung Mou Group, we focus on the overseas marketing development. And based on our parent company’s manufacturing capability and resources, YiTai also expended machining services such as die casting, injection molding, aluminum profile extrusion, 3D printing, which are committed to providing customers with one-stop purchasing services and experience.

CNC MACHINING , CNC MILLING , CNC TURNING , SHEETMETAL , FASTENER , OTHERS