What is the recommended cutting angle for extremely hard materials during drilling?

When drilling extremely hard materials, the recommended cutting angle is around 70 degrees. This angle is optimal because it balances the need for effective penetration into the workpiece while minimizing tool wear and heat generation, which is critical when dealing with hard materials.

A cutting angle of 70 degrees allows for a sharper point that can better initiate the drilling process, helping to reduce the force required to start drilling. This aspect is particularly important for hard materials, which can cause excessive wear and tear on the drill bit if the angle is too blunt. Additionally, this cutting angle helps to create an effective chip formation, allowing for better removal of debris from the hole, which can otherwise impede the drilling process and lead to overheating of the drill bit.

Other angles might not adequately address these concerns, as they could lead to increased friction, heat, and reduced efficiency in cutting hard materials.