What are Screws and Bolts?

Screws and bolts are very similar but also have some major dissimilarities. They are types of fasteners typically made of metal. A helical ridge known as a male thread (external thread) characterizes them.

A bolt can pass through unthreaded holes in parts and is secured by a nut, unlike a screw that mates with a threaded hole in one of the parts being fastened.

We use screws and bolts to fasten materials of various types, including metal, plastic, rubber, and ceramic. To use them, align the screw thread with the internal thread of a corresponding part. Well, in this reading, we’ll explore what screws and bolts are, their applications, diagrams, types, and differences between them. We’ll also explore their advantages and disadvantages.

Let’s begin!

Screws are a broad category of mechanical fasteners with a threaded shaft, designed to screw into a part. Often, they exhibit self-threading, also known as self-tapping, in which the screw inserts the thread into the material upon rotation.

It creates an internal thread that pulls the fastened material together and prevents pull-out. Screwdrivers commonly fasten a variety of materials, including wood, sheet metal, and plastic, with different types of screws.

The tapered shaft of the wood screws and self-topping screws features sharp threads that aim to sever a mating thread in the object they secure. There is also a machine screw, which is more like a bolt but has its entire shaft threaded.

Bolt and screw can be accurately known by their applications. A nut secures a bolt, which can pass through an unthreaded hole in the part. In contrast, a screw fits into a threaded hole in one of the fastened parts.

When a fastener is not self-tapping and only has part of its shaft threaded, we refer to it as a bolt. They are normally known as screws if the fasteners are either self-tapping or have their entire shaft threaded.

Screws rely on friction at the threads to remain securely fastened. In a self-tapping screw, radial expansion of the hole causes much of this friction.

In the case of machine screws, the friction is mostly caused by axial force resulting from the torque applied to the head and the subsequent tension in the screw combined with compression of the parts.

You can also use a locking nut or thread-locking adhesive to prevent machine screws from loosening.

Applications of Screws and Bolts

Today, screw and bolt applications are common due to their greater benefits over other joining processes. In fact, we can design almost all industrial applications to use the fastener, but we must consider some factors.

Considerations include threading, the applied load on the fastener, the stiffness of the fastener, and the required number of fasteners.

When choosing a fastener for a given application, some things must also be put into consideration. These include: accessibility, installation process, environment occurrences such as temperature, potentially corrosive elements, and water exposure., weight restrictions, and materials to be joined

Common applications of screws and bolts around us include chairs, tables, studs, doors, windows, kitchen utensils, electrical devices, etc. Broad uses of fasteners are automotive industries, aviation, agricultural equipment, marines, etc. in fact, anywhere equipment is dealt with, fasteners are always put into consideration.

Applications of screws and bolts around us include chairs, tables, studs, doors, windows, kitchen utensils, electrical devices, etc. Broad use of fasteners in the automotive industries, aviation, agricultural equipment, marines, etc.

Parts of a Bolt

The major parts of a bolt include head, shank, grip length, threading, thread length, and nominal length.

The head of the bolt is the top part that serves as a gripping surface for tools. When the appropriate bit grips the head, it serves to tighten and loosen the bolt. Bolts have a shank that is located under their head, and they are smooth and unthreaded.

This part stops the radial movements of the joined workpieces and eliminates the possibility of the bolt loosening. This is important because some workpieces generate vibrations and others are exposed to vibration in their applications.

The grip length of a bolt accommodates the components of the application and is equal to the combined thickness of the joining parts. One of the major parts of a bolt is threading, which facilitates the driving of a bolt into a workpiece.

Some bolts only accommodate the nut, not the entire thread length. However, the nominal length is the sum of thread length and grip length.

Diagram

Types of Screws and Bolts

Below are the various types of screws and bolts.

1. Decking screws

2. Pan-head screws

3. Hex cap screws

4. Carriage bolts

5. Lag bolts

6. Hammer drive screws

7. Square head bolts

8. Socket-head cap screws

9. Oval head screws

10. Wood screws

11. Sheet metal screws

12. Thread-rolling screws

13. Socket-head screws

14. Set screws

15. Weld screws

16. Raised or slotted cheese screws

17. Fillister head screws

18. Drywall screws

19. Concrete or masonry screws

20. Machine screws

21. Modified truss screws

22. Washer-faced screws

23. Thread-cutting machine screws

24. Self-drilling SMS

25. Self-tapping screws

26. Framing screws

27. Tamper-resistant screws

28. Sex bolts

29. Eyebolts

30. J-bolts

31. U-bolts

32. Shoulder bolts

33. Elevator bolts

34. Hanger bolts

Types of Bolt Head

Below are the various types of bolt heads:

Flat bolt head
Oval bolt head
Pan bolt head
Truss bolt head
Round bolt head
Hex bolt head
Hex washer bolt head
Slotted hex washer bolt head
Socket cap bolt head
Button bolt head

Major Difference Between Screw and Bolt

Universally, there is no accepted distinction between a screw and a bolt; however, there is a simple distinction that is often true, although not always. The fact is that a bolt passes through a substrate and receives a nut on the opposite side. On the other hand, the screw takes no nut since it threads directly into the substrate.

In summary, a screw fastens into a specific object, while a bolt can connect multiple items together. Therefore, while screws don’t require nuts for application, bolts often come with corresponding nuts. The difference between bolt and screw is likely due to regional or dialectical differences.

Furthermore, the machinery’s handbook describes screw and bolt distinctly. A bolt is an externally threaded fastener designed or inserted through holes in assembled parts.

Typically, torquing a nut tightens and releases the screw. A screw is an externally threaded fastener designed to be inserted into holes in assembled parts of mating with a preformed.

Difference Between Screw and Bolt in Tabular Form:

Feature	Screws	Bolts
Definition	Drilling into materials allows us to use fasteners with a helical ridge, known as a thread.	Fasteners with a threaded shaft are typically used with a nut to join materials together.
Primary Use	Directly fasten materials by creating their own threads in the material.	The nut is used to secure materials together.
Threading	The shaft has either full or partial threading.	It is partially threaded with a smooth shank.
Installation	They are typically driven into material with a screwdriver or similar tool.	They are inserted through pre-drilled holes and secured with a nut and sometimes a washer.
Holding Method	Their engagement with the material held them in place.	The material is secured by the tension between the bolt, nut, and material.
Tool Used	Use a screwdriver, Allen key, or a similar tool.	Use a wrench, socket set, or similar tool.
Types of Heads	There is a variety of head types (flat, round, pan, oval, etc.) and drive types (slotted, Phillips, hex, etc.).	The heads are typically hexagonal, but they are also available in other shapes.
Applications	Woodworking, drywall installation, and light construction.	The industries include heavy construction, machinery, automotive applications, and structural connections.
Examples	Wood screws, sheet metal screws, self-tapping screws.	Hex bolts, carriage bolts, anchor bolts.
Pre-drilling Required	Often do not require pre-drilled holes.	Usually require pre-drilled holes.
Strength	Generally lower tensile strength.	Generally higher tensile strength.

Advantages And Disadvantages Of Screws and Bolts

Advantages:

Weight reduction in the component is typically achieved.
Ability to join high-strength steel up to a tensile strength of Rm = 1500 MPa.
Minimum space requirements are needed within the tool.
Tool maintenance is easy and simple.
Capable of joining a wide range of sheet metal thicknesses with only one nut type, t = 0.5 to 5mm.
All surface-coated sheet metal panels are feasible.
Easy and simple installation in every work direction.

Disadvantages

The disadvantages of screws and bolts are listed below:

Extra weight is added to the components.
Bond lines are obvious.
They require holes that weaken the components.
They carry all the load at specific points, which contributes to fatigue.
Difficulty of refastening
Corrosion, and
Force precision.

Conclusion

Screws are a broad category of mechanical fasteners with a threaded shaft, designed to screw into a part. They are often self-threading (also called self-tapping) where the thread goes into the material when the screw is turned.

A bolt passes through a substrate and takes a nut on the other side. Whereas the screw takes no nut since it threads directly into the substrate. But there is no universally accepted distinction between a screw and a bolt.

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