Introduction:
In mechanical engineering, joints are used to connect different components of a product. When a product is subjected to large vibrations, the choice of the joint type becomes crucial. Welded and threaded joints are two common types of joints used in engineering applications. In this case, the better option for withstanding large vibrations is a welded joint.

Explanation:
1. Welded Joints:
- Welding is a process in which two or more parts are fused together using heat and pressure. It creates a strong and permanent bond between the parts.
- Welded joints have high structural integrity and can withstand large forces and vibrations.
- The welding process ensures that the joint is free from any play or movement, making it more resistant to vibrations.
- Welded joints distribute the load evenly across the joint, reducing the concentration of stress and minimizing the risk of failure.
- Welded joints are commonly used in applications such as pipelines, bridges, and heavy machinery where high strength and durability are required.

2. Threaded Joints:
- Threaded joints involve using screws or bolts to connect two or more components.
- Threaded joints may have some degree of play or movement due to the gaps between the threads, which can make them more susceptible to vibrations.
- Vibrations can cause the threads to loosen over time, leading to potential failure of the joint.
- Threaded joints are commonly used in applications where disassembly or regular maintenance is required, such as in automotive or plumbing systems.

3. Comparison:
- Welded joints provide a stronger and more rigid connection compared to threaded joints.
- The welding process eliminates any potential play or movement in the joint, making it more resistant to vibrations.
- Threaded joints, on the other hand, may have some inherent movement due to the gaps between threads, which can amplify the effects of vibrations.
- Additionally, vibrations can loosen threaded connections over time, compromising the integrity of the joint.

Conclusion:
In conclusion, when a product is subjected to large vibrations, a welded joint is a better choice compared to a threaded joint. Welded joints provide a stronger and more rigid connection, eliminate any potential play or movement, and distribute the load evenly across the joint. This makes them more resistant to vibrations and less prone to failure. Threaded joints, on the other hand, may have some inherent movement and can be affected by vibrations, increasing the risk of loosening over time. Therefore, for applications with large vibrations, it is advisable to use welded joints.