What is the Difference Between a Screw and a Bolt?

The main difference is subtle yet important. As specified by the machinery's handbook, a bolt requires the aid of a nut and a pre-drilled unthreaded hole in order to be fastened to a component. Exceptions to this rule exist when using a nut plate or fixed threaded component. The way in which the externally threaded fastener becomes lock-tight relies on more external variables than that of a screw.

Our goal is to teach you the most important identifiers of our full range of fasteners and tools to ensure proper application and outcome every time. In this resource guide, we hope to broaden your knowledge of some of our favorite fasteners, bolts and screws. With thousands of bolt and screw variations including; materials, finishes, sizes, types, strengths, and more, these two fasteners are the most commonly used fasteners worldwide.

Showcasing recognizable external threading, both screws and bolts are designed to ensure a strong hold between two or more items. These items can be composed of a range of materials such as wood, metal, concrete, and plastics. Be confident when binding and locking in materials when using both bolts and screws. So, what is the difference between a screw and a bolt? And what are some of the advantages and disadvantages of each fastener? Below we will summarize each fastener to give you a complete understanding of all the features, uses, and pitfalls you'll encounter when using a screw or bolt. And when you are done reading, we hope you can have the confidence you need to pick the right fastener for you. 

What is a Bolt?

Classified in the “Threaded Fastener” category, bolts are an external male threaded fastener, generally requiring a matching female part like a nut. Bolts have many uses and applications making them a popular choice within the fastener industry. Designed to provide a strong and tight bond between two or more objects, bolts use the combination of their threaded exterior with the matching nut to grip and lock as they drive into wood, concrete, metal, and more. The most popular way to drive in a bolt is to use a wrench, different head shapes, sizes, and functions can be sourced to best fit the screw you're using. This diverse need for driving tools is due to the huge range of head types affixed to bolts, with dome, hex, and flat heads to name a few. BW Industrial Sales is proud to offer an ever-increasing catalog of quality bolts, nuts, and wrenches, all designed to get the job done right.
Bolts can be found in a large variety of materials, types, sizes, finishes, and strengths:

Material Options for Bolts

Steel (multiple grades), stainless steel, brass, bronze, and nylon plastic are common material types used to form bolts for an array of applications. These materials can determine a bolt's strength and resistance to corrosive agents. It is extremely important to choose the right material bolt to ensure a successful lifelong bond. 

Bolt Types

Bolts can be classified in a wide variety of types including anchor, arbor, bent, carriage, elevator, flange, frame, hanger, hex, machine, J-bolts, lag, Rock, step, structural, sex/chicago, shoulder, tap, track, timber, toggle, plow, stove, eye, U-bolts, Cane, and more. Due to the large range of shapes and uses, some bolts are interchangeable with similar style screws, based on intended use.

Bolt Finishes

Finishes for bolts include; zinc, nickel, phosphate, chromium, cadmium, gold, and more. Finishes typically assist in a bolts ability to avoid corrosion and some increase the exterior strength and look of the fastener. See our Finishes and Coatings resource to learn more.

Bolt Strength and Classification

The strength and classification of bolts help identify the ability of a specific bolt. Using material, size, and finish as factors, each bolt is given a strength rating and classification to allow easy identification and ensure proper application. It is extremely important to make sure the bolt used for a specific purpose is certified and recommended for that use.

Head Types

Bolt head types are the shapes fitted to the top of each bolt thread, with dome, hex, round, button, flat, and variations of each head type, it's important to know which drive tool you need for every type of bolt. Some head types are designed to fit the look or flush finish desired by users, others are built to increase the maximum torque and grip to ensure a solid lock.

Drive Types

Drive types define the way in which the bolt or other fastener is driven into the desired object. Designed into the head of a bolt, drive types usually include hex, philips, slotted, combo, socket, square, star, pozi, and other variations of similar shapes. Drive types determine what tool to use when applying the bolt.

Advantages and Characteristics of a Bolt:

  • Provides a superior lock-tight capability when used with a nut
  • Designed to service industrial and structural needs
  • Typically, thicker and stronger
  • Larger range of head and drive types
  • Strength longevity
  • Require prefabricated holes to use
For more information on bolts and to answer any specific questions you may have please feel free to contact our team and we will be happy to help find an answer for you. If you can't find the bolt you need we can have it custom manufactured to your exact specifications, check out our custom fasteners page for more information.

What is a Screw?

While still in the “Threaded Fasteners” category, unlike a bolt a screw does not require a nut to be secured. Instead, screws are threaded directly into the object that it is intended to stabilize. There are many different types, including wood screws, sheet metal screws, hex cap screws, eye screws, twin fast screws, drywall screws, machine screws, and many more. They come in all sorts of lengths and widths depending on the need. Another unique feature of the screw is that the shape of the head can vary depending on the intended use. Whatever your project entails, there is bound to be a screw just for you. While a screw can be made from just about any material, the most common and most trusted material of screw is simply steel. 
There are varying types of screw materials, drive types, sizes, finishes, and strengths: 

Material Options for Screws

Screw materials are similar to bolts and most fasteners in that screws are available in almost all material types, most typically fashioned in steel, stainless steel, brass, bronze, and nylon plastic. Choosing the right material for your screw is highly important and will determine factors like corrosion resistance and strength. and resistance to corrosive agents. 

Screw Types

Types of screws range largely with cabinet, cap, concrete, drywall, dowel, drive, eye, flange, hex jackscrew, lag, machine, self-drilling, self-piercing, self-tapping, sems, socket, thread-cutting, thread-rolling, thumb, wing, weld, and wood screws to name some. With so many to choose from, screws are highly popular and used in many kinds of applications. 

Finishes and Coatings

Finishes and coating options for screws are similar to those available for other fasteners like bolts and nuts. These finishes can increase strength, corrosion resistance, color, size, and more. Some of the most popular finishes for screws include zinc, phosphate, nickel, chromium, gold, cadmium, and more. Explore our Finishes and Coatings resource PDF to find out more.

Strength and Standards

Screw strengths range to accommodate most applications. Choosing the right strength for your screw is extremely important and can be the difference between a job well done or one that'll come back to bite you. For more information on strength, standards, and classifications see our resource. 

Head Types

Screw head types are designed for a large array of application styles, drivability, and finishing looks. Screws have a large catalog of possible head types to choose from including; bugle, fillister, flat, bind, undercut, hex, truss, oval, pan, round, washer, trim, and more. There is always a head type to match your needs. For more information see our Head and Drive type Resource.

Drive Types

Drive types of screws are similar to that of bolts, with a varying range of looks and application styles. Typically pressed into the head, drive types include combo, phillips, slotted, hex, combo, square, socket, 6-lobe, and other variations and shapes. When driving in a screw a different tool head may be necessary to attach to the specific drive shape screw you’re using. See our Head and Drive type Resource to learn more

Benefits and Characteristics of a Screw:

  • Easy to use
  • No need to predrill a hole
  • Available in small & micro sizes
  • Does not need an assisting fastener like a nut to ensure a strong hold
  • Small range of drive types allows for universal ease of use
  • Compatible to a large array of universal applications

Get Started with BW Industrial Sales Today

Our team of experts is standing by and ready to assist with all your questions and inquiries. With over 100 years of combined knowledge within the fastener industry, BW Industrial Sales is here to provide you with all the useful tools and resources you need to make the right fastener-related decision for you. We make sure commonly asked questions have a well-thought-out and detailed response with the hope that all our customers can leave our website with the knowledge they came looking for.

To find out more information on screws and similar fasteners contact our team and we will be happy to help you find the correct fastener for your application. If you don't see the specific screw you need, don't worry we can help, check out our custom fastener page and submit an inquiry to our team of experts with your exact specifications and requirements. 
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