A drill bit must have an included angle of how many degrees?

The correct angle for a drill bit, specifically for common twist drill bits used in metalworking applications, is 118 degrees. However, a drill bit with an included angle of 135 degrees is often found in specific applications such as drilling into softer materials or for creating a larger hole. This angle helps reduce the cutting forces and keeps the bit from binding in the material, allowing for smooth operation.

A 135-degree drill bit is particularly effective for applications that require less penetration force, making it suitable for various tasks like producing larger holes or when working with materials that may chip or splinter. The increased angle facilitates easier chip removal and improves the drilling process's efficiency.

The other angles provided typically do not adhere to the standard for general-purpose drill bits or are less common in typical applications. Thus, the choice of 135 degrees reflects a balance between effective cutting and reduced friction during drilling.