Why is copper tube not typically threaded?

Copper tube is not typically threaded primarily due to its thin wall. The wall thickness of copper tubing is generally not sufficient to withstand the stresses that are introduced during the threading process. When a pipe is threaded, material is removed to create the threads, which can further reduce the wall thickness and compromise the integrity of the tube. This can lead to potential issues such as leaks or failure under pressure.

Additionally, the mechanical properties of copper make it unsuitable for threading in many applications. It is softer and more malleable compared to other materials used for threaded pipe, which can lead to difficulties in creating a perfect thread that maintains a strong connection.

Other options discuss aspects like cost, application, and compatibility with fittings, but these are not the primary reasons. While copper can be more expensive, and often used for low-pressure applications, these factors do not directly influence the threading capability. Similarly, while there are fittings that can match copper tubing, the thickness and nature of the material remain the significant factors against using threads on copper tubes.