ANS:C - drilling

Drilling is a machining process used to create holes in solid materials. It involves the use of a rotating cutting tool, called a drill bit, which applies a downward force while rotating to remove material and create the hole. Drilling is one of the most common and fundamental machining operations, used in various industries and applications, including manufacturing, construction, woodworking, metalworking, and more. Here's a breakdown of the drilling process:

1. Preparation: Before drilling, the workpiece is securely clamped to prevent movement during the operation. Proper alignment and positioning are crucial to ensure accurate hole placement.
2. Selection of Drill Bit: The appropriate drill bit is selected based on factors such as the material being drilled, hole size requirements, and the desired hole geometry. Drill bits come in various types and sizes, including twist drills, center drills, flat-bottom drills, step drills, and more.
3. Drilling Operation: The drill bit is attached to a drilling machine, which could be a hand-held drill, a drill press, or a CNC machining center. The drill bit is brought into contact with the workpiece surface at the desired location.
4. Rotation and Feed: The drill bit is set into rotation while simultaneously applying a downward force (feed) to penetrate the material. The rotation of the drill bit cuts into the workpiece, generating chips or swarf that are removed from the hole by the flutes of the drill bit.
5. Cooling and Lubrication: Depending on the material being drilled and the cutting conditions, cooling and lubrication may be necessary to dissipate heat and reduce friction. This helps prolong tool life and improve machining efficiency.
6. Completion: Once the desired hole depth is reached, the drilling operation is stopped, and the drill bit is retracted from the workpiece. The resulting hole may require further finishing operations, such as deburring or chamfering, to remove any rough edges or burrs.

Drilling can be performed on a wide range of materials, including metals, plastics, wood, composites, and ceramics. It is a versatile process capable of producing holes of various shapes, sizes, and depths to meet specific design requirements. Additionally, drilling can be automated using CNC (Computer Numerical Control) machines for high precision and productivity in large-scale production environments.