Why is a slow, constant, circular sweeping motion recommended during preheating?

A slow, constant, circular sweeping motion during preheating is crucial for achieving uniform heating of parts. This method ensures that heat is distributed evenly across the workpiece, preventing any localized hot spots that could lead to stress or warping. When heat is applied evenly, it helps maintain the integrity of the materials being joined, particularly in processes like silver brazing where precise temperature control is essential for optimal results.

By using a circular motion, the heat source impacts a broader area of the workpiece rather than concentrating on one specific spot. This approach is necessary not only for the proper melting of filler materials but also for minimizing the risk of thermal shock, which can occur if particular areas reach high temperatures while others remain cold. Overall, this technique enhances the effectiveness of the brazing process, leading to stronger, more reliable joints.