What is the purpose of annealing the hole when drilling through hardened metal?

The purpose of annealing the hole when drilling through hardened metal is primarily to soften the material for easier drilling. When metal is hardened, it becomes more difficult to drill through, which can lead to increased wear on the drill bit and potential tool damage. Annealing involves heating the metal to a specific temperature and then allowing it to cool, which alters its microstructure, making it less rigid and more ductile. This process reduces the hardness of the metal, making it easier for the drill bit to penetrate and reducing the risk of breakage or damage during the drilling process.

In the context of drilling through hardened materials, this technique can significantly improve efficiency and extend the life of the drill bit, as it allows for smoother cutting and reduces the amount of force needed to create the hole.