Before welding in switches, what must be done to the switch points?

The correct choice emphasizes the necessity for switch points to be centered and square before the welding process begins. This step is crucial as proper alignment ensures that the switch operates effectively and reliably after the welding is completed. When the switch points are centered, they will make better contact, reducing the likelihood of electrical issues or mechanical failure. Additionally, being square means that the points are at the correct angles, contributing to the overall functionality and safety of the switch mechanism.

Having centered and squared switch points also facilitates a more controlled and uniform weld, which is essential in thermite welding. An improper alignment could lead to uneven heating and cooling, compromising the integrity of the weld and potentially leading to future failures. Therefore, ensuring that switch points are both centered and square is a fundamental step in the preparation for thermite welding, setting the foundation for a successful and durable weld.