Most spot welds are specified by what measurement?

Spot welds are typically specified by their diameter because this measurement directly relates to the size of the weld nugget, which is the area where the materials are fused together. The diameter indicates the size and strength of the weld, which is critical for ensuring the structural integrity of the materials being joined. A larger diameter generally corresponds to a stronger weld, making this measurement essential for quality control and engineering specifications in welding practices.

In contrast, while length, width, and thickness may be relevant measurements in other contexts, they do not provide the same specific insight into the effectiveness of a spot weld as diameter does. Length and width would apply more to the dimensions of the materials being welded rather than the weld itself, and thickness could relate to the materials involved rather than the actual weld connection. Thus, diameter remains the most relevant and standardized way to specify spot welds.