When drilling stainless steel, what should the included angle of the drill be?

When drilling stainless steel, the included angle of the drill bit is crucial for achieving efficient cutting and preventing damage to both the drill bit and the material. The optimal included angle for drill bits used on stainless steel is generally around 135 degrees. This angle strikes a balance between providing sufficient cutting edge to manage the hardness of stainless steel and reducing friction to help with chip removal.

Using a drill bit with a 135-degree angle enables better penetration and allows for a more effective cutting action on the tough material. In addition, drilling at a lower speed is typically recommended for stainless steel to minimize heat buildup and to prevent work hardening of the material, which can make drilling increasingly difficult as the process continues.

Considering the other options, a 90-degree angle may not provide adequate cutting edge for the hard material; 118 degrees is more suitable for softer materials; and while high speeds might be effective for other metals, they are generally not advisable for stainless steel without proper cooling and cutting fluid, making 135 degrees at a low speed the most effective choice.