The standard countersink angle is typically 90 degrees.
A countersink is a conical hole cut into a material to allow the head of a screw or bolt to sit flush with or below the surface. The angle of the countersink refers to the angle of the cone-shaped hole. Here's an explanation of the three mentioned angles:
A 90-degree countersink is the most common and widely used. It forms a cone with a 90-degree angle, creating a V-shaped recess. This is suitable for a variety of applications and materials, providing a standard and versatile solution. This can be useful in situations where a more gradual slope is preferred. It might be used when working with softer materials or when a more aesthetically pleasing finish is desired.