Who is correct about using a body file versus a high-speed grinder on body filler?

When it comes to the use of a body file versus a high-speed grinder on body filler, Technician A is correct because body files are specifically designed for shaping and smoothing body filler. They allow for a more controlled and precise removal of material, which is essential for achieving a flat and even surface. This meticulous approach minimizes the risk of removing too much filler and ensures that the repair maintains the correct contour, which is crucial for both aesthetics and aerodynamics.

On the other hand, high-speed grinders, while useful for other applications, can generate excessive heat and remove material too rapidly, which can lead to inconsistent surface quality and even damage to the underlying substrate. Their use may also create a risk of sanding through the filler or distorting the surface. Therefore, it's important to choose the appropriate tool for the job; in this case, the body file is the preferable tool for finishing body filler work effectively.