Name three general classes of drilling.

The three general classes of drilling, which include percussion, rotary, and combination percussion rotary, represent fundamental methods used in drilling operations across various applications.

Percussion drilling involves a hammering action that drives the drill bit into the material, making it effective for penetrating hard surfaces, such as rock and dense soil. This method utilizes a rapid upward and downward motion, allowing the bit to break through the material efficiently.

Rotary drilling, on the other hand, employs a rotating bit to grind or chip away the target material. This technique is versatile and widely used in both soft and hard rock scenarios, providing a continuous and efficient means of drilling deep holes.

Combination percussion rotary drilling incorporates elements from both percussion and rotary methods. This hybrid approach allows for the benefits of both techniques: the rapid penetration of percussion drilling and the effective material removal of rotary drilling. This method is often employed in challenging conditions where a single drilling method might not be as effective.

The other choices, while they encompass different aspects of drilling, do not properly classify the three main drilling categories recognized in industry standards. Choices that focus on hand tools, electric, or pneumatic systems relate more to the power source and not to the actual classes of drilling methods themselves. Thus, the combination of percussion,