Threaded Connection Method - The Difference And Use Of Internal Thread And External Thread

In daily life and industrial production, threaded connection is almost everywhere, from home water pipes to the assembly of machinery and equipment, threads are an indispensable key part. There are many forms of threaded connection, among which internal thread and external thread are the two most common types. So, what is the difference between them? What scenarios are they suitable for? Today we will talk about the difference between internal thread and external thread and their uses.

 

1. Definition of internal thread and external thread

First of all, we have to figure out what is internal thread and what is external thread.

Internal thread refers to the thread that appears inside the hole. Simply put, it is to process the thread in a circular hole, and the corresponding external thread object can be inserted. Common examples are the inside of the screwdriver handle or the interface part of the water pipe.

External thread refers to the thread that appears on the outer surface of a circular object. It is the part that can be screwed into the internal thread, like the outer surface of the common screws and bolts is the external thread.

It can be understood that the internal thread is the thread formed in the hole, while the external thread is the thread on the outside of the object.

 

2. The difference between internal and external threads

Although both internal and external threads are part of threaded connections, their structures, uses and applicable scenarios are very different.

Structural differences: A significant difference between internal and external threads is their structure. The internal thread is a spiral groove located in the hole; while the external thread is a spiral protrusion located on the outer surface of the object.

Processing method: The processing methods of internal and external threads are also different. Internal threads usually need to be processed with a special tool-internal thread cutter, which is relatively complicated to operate. External threads can be made using external thread cutters or thread rolling machines.

Scope of application: Internal threads are generally used to match connection parts that require load-bearing capacity, such as water pipe joints, threaded holes, etc. External threads are more used in parts that can be screwed into other objects, such as bolts, screws, brackets, etc.

 

3. Purpose of internal threads

Internal threads are mainly used to connect "a hole" and "external objects" in two objects. In practical applications, internal threads are often used in conjunction with external threaded parts. Common applications include:

Pipeline connection: such as the connection between water pipes and gas pipes, internal threads are often used in pipe joints to ensure that pipes can be firmly connected.

Mechanical equipment connection: Some machines and equipment need to connect other parts through internal thread holes, such as the connection between motor housing and other metal parts.

Furniture assembly: Some connectors in furniture, such as the support parts of bed frames and tables, also often use internal thread connections to ensure stability.

 

4. Uses of external threads

External threads are the most common part of threaded connections, and their uses are also very wide, mainly reflected in the following aspects:

Fixed connection: External threads are often used in fasteners such as screws, bolts, and nuts. They can be screwed into internal thread holes to achieve the effect of fixing and connecting. This is the most basic function of external threads.

Adjustment and locking: In some mechanical equipment, external threads are also used to adjust the position of components, or to lock components by screwing into internal threads. For example, the adjustment bolts on the machine can adjust the height or angle of the component through external threads.

Packaging and sealing: External threads are also used in the packaging field. For example, some bottle caps are designed with external threads, and the sealing effect is achieved by rotating and fixing the bottle caps.

 

Usually, internal and external threads appear in pairs, and the cooperation between internal and external threads determines the strength and sealing of the connection. When in use, the number of threads, angles and sizes of the external threads need to be precisely matched with the internal threads to ensure a firm connection and no loosening. This is why the standardization of dimensions is particularly important in threaded connections. Understanding their differences and uses not only helps us choose the right threaded connection method, but also helps us better solve various problems in actual production. Whether in home life or industrial applications, the use of internal and external threads makes our equipment more stable and runs more efficiently.