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Bolts vs Screws

Bolts and screws are commonly used fasteners, and we treat them as one thing. Actually, they are two types of products. This article takes you to a detailed understanding of the differences between screws and bolts

Different definitions:

1、Bolt is a large fastener consisting of two parts, various types of heads and threaded shanks, which require nuts and washers to achieve better fastening effects and can also be repeatedly disassembled.

2、Screws, on the other hand, tend to be smaller in size and have a structure similar to bolts. Some screws do not require nuts and can be directly screwed into the surface of the object that needs to be fixed. However, there are also screws that need to be used in conjunction with nuts, just like bolts.

Different head shapes

1.There are various shapes of bolt heads, including hex head bolt,  flange head bolt,allen head bolt,round head bolt, square head bolt, eye bolt, u head bolt,T head bolt, etc.

Bolts with different head shapes have their own characteristics and applicable scenarios when used. For example, hexagonal bolts are easy to tighten with a wrench or socket tool and are commonly used for heavy-duty connections.

Allen head bolts are suitable for precision equipment,Round head bolts are used in situations with high aesthetic requirements,Square headed bolts provide greater torque transmission.Eye bolts can be used for suspension or connection,Flange head bolts are used to increase the connection area,T-head bolts are commonly used in special structures.

Different head shapes1

2.Screw heads have various shapes, including hex heads, round heads, flat/countersunk heads, cross heads, socket head, square heads, flange heads, etc. Special shapes such as triangles, ellipses, stars, etc.

According to different usage scenarios, screws can be divided into machine screws, self tapping screws, self drilling screw, drywall screws, wood screws, etc.

Different head shapes2

Differences in threads

There are differences in the shape, angle, purpose, strength, and processing method of the threads of bolts and screws.

The threads of bolts are mostly in the standard spiral shape, with an angle of usually 60 degrees.

They are mainly used for heavy-duty connections and are used in conjunction with nuts, resulting in high thread strength.

The thread shapes of screws are diverse, and the angle may be small. They can be directly screwed into the workpiece for fixation or connection, with relatively low strength. The processing method of threads is also different.

Different fastening tools

Different fastening tools

There are some differences in the use of tools between bolts and screws. Bolts usually require the use of tools such as wrenches, sockets, or torque wrenches to tighten or loosen them, which can provide greater torque to ensure the tightening effect of the bolts.

Screws, on the other hand, are usually installed and removed using a screwdriver or screwdriver, and the size and shape of the screwdriver need to match the head of the screw.

In addition, for some special types of bolts and screws, specialized tools may be required, such as using an Allen wrench for hex bolts and a Phillips screwdriver for Phillips screws. When using tools, it is necessary to choose appropriate tools based on the type of bolts and screws to avoid damaging threads or tools.

Differences in strength

The performance level of bolts can generally be divided into more than 10 levels, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc.

A higher strength bolt indicates that it can withstand greater loads. The strength of screws is relatively low.


In short, although bolts and screws have similarities, there are significant differences in their use, characteristics, and other aspects.

Understanding their differences can help us make more suitable choices in practical applications.