What is the secret technique for effective metal polishing?

The technique of working the abrasive at 90˚ angles over previous scratches is effective for metal polishing because it allows for a more thorough removal of scratch marks and imperfections on the metal surface. By crossing over existing scratches at a right angle, you enable the abrasive to engage more effectively with the material, reducing the depth of the scratches and resulting in a smoother finish. This method is particularly beneficial because it helps to break the continuity of the scratches, leading to a more refined surface texture.

Using high speeds could lead to overheating and potential damage to the metal, while applying pressure and moving in circles may not effectively address the scratches in a uniform manner. Lastly, polishing in a single direction doesn't correct imperfections comprehensively, as it simply continues existing scratches rather than eliminating them. Therefore, the 90˚ approach is a disciplined and structured method that maximizes the effectiveness of metal polishing, ensuring a high-quality finish.