Introduction

Do you know the difference between a deck that holds up for years and one that wobbles whenever someone steps on it? Fasteners.

Use the wrong one and you’re not just risking a loose joint but compromising the whole structure.

With 20 years as a Midwest-born pro handyman exploring garages and race pits, I have seen too many good projects fall apart because of unfit fasteners. My goal with Westland Fasteners is to offer great advice that saves you time, money, and headaches.

In this post, we’re diving into the trio of every DIY job: bolts, nuts, and washers. If you’ve ever wondered:

• Why can’t I just reuse this nut?
• What size washer goes with what bolt?
• Do I really need to worry about using a torque wrench?

You’re in the right place. We’ll cover the essential types of each fastener, how to pair each type, and share practical tips on picking the right ones.

Bolts

Bolts are a type of fastener that comes in a wide variety of shapes and combines pieces of material.

Here are common types of bolts.

1. Hex Bolts

   

   Hex bolts (sometimes called hex cap screws, tap bolts, or hex head screws) are the most common bolt type.

   They are characterized by their six-sided hexagonal-shaped head, providing a strong point of contact for a wrench. This head type offers a wider surface area for clamping and a secure grip for tightening.

   Hex bolts can either be fully threaded (the entire shank has threads) or partially threaded (having an unthreaded area under the head).

   Uses: Due to their shape, hex bolts are often used in construction, furniture, or electrical and plumbing systems. Common applications include:

   • Securing structural components (like beams and columns)
   • Fastening heavy equipment parts
   • Assembling car engine components
   • Mounting solar panels.

2. Carriage Bolts

   Carriage bolts are recognizable by their smooth, large-diameter head. The bolt gets its name from the 1800s, when they were used to construct carriages and assemble complex carriage parts.

   Its unique design allows you fasten it without needing another tool to hold the head. Thanks to their round heads and square neck underneath the shank, the bolt prevents turning during tightening and is ideal for situations where access is only possible from one side. As a result, carriage bolts work well with wood and other soft materials.

   Uses: Carriage bolts are used in woodworking, fencing, and metalworking applications. They can fasten metal to wood, wood to wood, or metal to metal when there’s a pre-drilled hole. They are the best bolts for building gates, fences, decks, furniture, boats, and other purposes involving joining wood and metal.

3. Lag Bolts

   

   Lag bolts (also called lag screws) are heavy-duty screws used where significant holding power is needed.

   They are often made from galvanized steel (stainless steel or other corrosion-resistant materials). Lag bolts come with hexagonal heads and are coarse-threaded to improve grip and torque when tightened. Due to their intrinsic strength and durability, these bolts are widely known to be extremely strong and tough.

   Since they’re threaded directly into the material using a wrench or impact driver, lag bolts don’t need nuts to be fastened. Their coarse threads grip the material tighter than traditional screws to provide a strong connection. One upside to using them is that they provide stability even in high-stress applications and extreme pressure environments.

   Uses: Lag bolts are commonly used in heavy construction and woodworking projects. They are used to:

   • Secure posts to concrete
   • Build fences or decks
   • Attach ledger boards to houses

4. Flange Bolts

   Flange bolts are small-diameter bolts that connect two components in a fixed position.

   The flange has a wide, flat surface that extends from the bolt’s head and distributes the clamping force over a larger area. Its hexagonal head has a retainer ring that connects to the component using a socket. With this wide area design, there’s a more secure connection and no damage to the fastened materials.

   A major strength of these bolts is their size and sealability. This prevents leakage and provides additional structural integrity, making them versatile for various applications. To keep your bolts in top condition, I recommend using high-quality rust prevention products, especially in outdoor or high-humidity environments.”

   Uses: Flange bolts are generally used in the automotive and construction industries where vibration is an issue. Some examples include:

   • Joining frame components in an airplane
   • Securing pipe flanges
   • Fastening various machinery parts

Nuts

Nuts are a type of fastener with a threaded hole designed to be paired with a bolt or screw.

Here are the common types of nuts:

1. Hex nuts

   

   Hex nuts are a common general-purpose nut with internal screw threads designed to be tightened or loosened with a wrench or socket.

   It’s one of the most common nuts, mostly paired with hex bolts to fasten materials together. Hex nuts get their name from their hexagonal shape—six flat sides and six corners. They have an internal threaded hole, which allows it to be screwed onto a threaded bolt or rod.

   Uses: Hex nuts are used with hex bolts to:

   • Secure engine components
   • Secure bolts that hold furniture pieces together
   • Fasten lighting fixtures to walls
   • Tighten airplane engine components.

2. Lock Nuts

   Lock nuts are engineered to resist loosening under vibration or torque.

   They are specifically designed for vibration-prone and safety-critical applications such as wheel machines, vehicles, and other equipment where secure connections are essential.

   Unlike regular nuts, lock nuts prevent loosening by creating friction or a positive locking mechanism. Their unique design requires a special key for removal and provides additional security. For precision, many professionals rely on Milwaukee power tools to install them with ease.

   Some lock nut types in widespread use include:

   • Nylon insert lock nuts (Nylock nuts) are the most common lock nut type with an inner sleeve that molds to the threading pattern. It uses a nylon insert that deforms when the nut is tightened to create friction and prevent loosening.
   • Hex jam nuts use a double-nut system and are thinner than standard hex nuts. They are often used as a second nut to lock the first in place, in which two pieces are tightened against one another.
   • Castle nuts have slots cut into one side. They are used with a cotter pin to prevent the nut from loosening.

   Uses: Lock nuts prevent fasteners from loosening in environments that experience vibration or any other forces. This makes them crucial to the safety of heavy equipment in automobiles and the construction industry. Use cases include:

   • Securing wheel nuts
   • Keeping auto engine parts in place
   • Anchoring structural components.

   Read: How to tighten lug nuts correctly

3. Flange Nuts

   

   Flange nuts are characterized by a flanged design, with a protruding rim on one side while the other looks like a traditional nut.

   The protruding rim side is a built-in washer, so you don’t need to use a traditional nut with a separate washer.

   Their protruding rim allows flanged nuts to cover and press against a larger surface area than traditional nuts. At the same time, the flanged nut will distribute the load more evenly.

   Flange nuts are combined with bolts or threaded fasteners with a compatible thread pitch and size. Common bolt pairings include hex head bolts, socket cap screws, carriage bolts, and stud bolts.

   Uses: Flange nuts are often used in fastening for oversized holes. They are used for:

   • Engine assemblies
   • Transmission connections
   • Assembly lines
   • Ship components

Washers

Washers are thin, flat discs usually made of metal with a hole in the center. They are paired with bolts, screws, or nuts to distribute load and prevent surface damage.

Common types of washers include:

1. Flat Washers

   

   Flat washers are also known as type A plain washers and are the most basic type of washers.

   They are circular, flat, and vary in thickness. One distinction about them is the presence of a central hole to accommodate the bolt. This way, the washer can distribute force and increase the bolt’s bearing surface area to prevent it from coming loose.

   Since they vary in size, misplacing them can be a real pain. So, keep them sorted in a Milwaukee tool chest to ensure you always have what you need.

   Flat washers are used distributing for general-purpose load. They help maintain structural integrity and reduce friction between fasteners and materials.

2. Lock Washers

   

   Lock washers come in either a split, coiled, or star shape. They are made of metal or stainless steel but can also come in aluminum or bronze.

   This washer works by preventing a bolt from rotating or loosening due to torque, effectively locking it firmly in place.

   Most DIY mechanics I’ve spoken to use hex bolt and lock washer combination for minor vehicle repairs. Sometimes this fix works, but when it doesn’t? Don’t push it. It’s always smart to call to tow a car to the repair shop rather than driving with loose hardware.

   Lock washers are often used when joining components in cars, planes, washing machines, and marine vessels, as fasteners can easily loosen due to vibration in these applications.

3. Fender Washer

   A fender washer is a type of flat washer with a significantly larger outer diameter than its inner diameter. They are flat, circular pieces of metal with a hole in the center for a bolt or screw.

   This design allows the washer to distribute the load over a larger area. The larger outer diameter spreads the force of the fastener over a wider area and prevents damage to the surface underneath. The washers are typically made from steel, stainless steel, or other metal materials.

   Fender washers are used when a fastener needs to connect to thin or softer materials. They connect parts of sheet metal work, plumbing, electrical installations, and auto body repair.

4. Split Ring

   Split ring washers have a break or split in their design, which creates two sharp edges.

   They are a specialized washer that prevents bolts and nuts from loosening due to vibration. When tightened, the split ends of the washer compress and exert a spring-like pressure against the nut and bolt head to create a locking action.

   Split ring washers are used over traditional flat washers for better protection against vibrations. Machines and equipment that often produce vibrations need split washers so their bolts don’t loosen or come out completely.

   Split washers can prevent bolts from loosening due to vibrations. As a machine or equipment vibrates, the split washer will push back into it. They are ideal for vibrations because they prevent the bolts used with them from loosening.

Where do washers matter most?

Washers may seem like small, insignificant pieces. But they are crucial for fastening delicate or softer materials such as soft wood, sheet metal, and plastic. They distribute the load, ensuring a safe connection.

Here’s a rundown of where washers matter most:

Application	Purpose	Recommended washer choice
Soft Materials (Wood, Plastic, Drywall)	Distribute the load and prevent the fastener head from being damaged.	Flat/Fender washers
Suspension & Automotive	Secure bolts that might loosen in high-vibration environments.	Lock/Spring washers
Sheet Metal	Increase surface area to spread force and keep the fastener secure.	Flat washers
Electrical Connections	Protection installation from corrosion caused by metal-on-metal contact.	Nylon/Fiber washers

How to Choose the Right Fastener (What You Need to Know)

Whether you’re assembling furniture or handling construction, here are some tips to help you pick the best bolt, nut, or washer for the job:

Materials

The materials you’re joining will determine the right fasteners to use.

For instance, metal fasteners should be used on materials of the same metal type. Stainless steel fasteners can be used with stainless steel materials or non-metallic materials. Ensure the material doesn’t react negatively with the fastener material before deciding.

Strength

The fasteners you choose must be strong and durable enough to withstand the load and stress they may encounter.

Every fastener offers different load-bearing strengths, so research before choosing one.

Size, Type & Shape

The size and shape of the fasteners must be appropriate for the materials being joined.

The head type, diameter, or thread should be chosen depending on the type/thickness of materials being joined.

Installation Method

Lastly, the installation method should be considered when choosing a fastener. For example, if there’s limited access and you can’t reach the backside of the material, a self-tapping screw or threaded inserts may be a better choice than a bolt. Also, consider pairing your fasteners with the best cordless drill to save time and energy.

Understanding bolts and nuts is one thing; knowing how to use them properly is another. To know how to tighten your fasteners properly, read:

• An introduction to torque and tightening
• How to use a torque wrench

FAQs on Bolts, Nuts, & Washers

How do you match a washer to a bolt?

Match the washer’s inner hole around the bolt’s shank and ensure it fits snugly.

If the hole is too big, it won’t distribute force evenly. Also, the outer diameter determines how much surface area the washer covers, so choose a washer with a bolt that fits your materials.

What are the three basic types of threads?

The three basic types of threads are Coarse, Fine, and Special.

Coarse threads have a larger pitch (distance between threads), which indicates fewer threads per inch. Fine threads have a smaller pitch (more threads per inch), providing greater strength and precision. Special threads are designed for unique applications.

How to identify a bolt type?

First, determine if it’s a metric or a standard (SAE) bolt. Metric bolts often have a numerical marking on the head (8.8, 10.9, etc) while standard bolts may have lines or markings (lines, slashes, or dots) on the head to indicate their grade.

Plus, bolts can be classified by shape (hex head, socket head, square head, etc.) or material.

What is the most common type of bolt?

A hex bolt is the most common type of bolt. These widely used bolts have a six-sided hexagonal head and are designed to be tightened using wrenches or sockets.