Cast iron ( hard ) based on Rankine Theory, introduce for brittle material. Segmental chips are formed while machining. Discontinues chips - due to low cutting speed & small Rake angle.

so Option B is correct.

Explanation:

When machining a hard and brittle metal like cast iron, the type of chips produced is discontinuous chips. This is due to the inherent properties of cast iron and the nature of the machining process.

Properties of Cast Iron:
1. Hardness: Cast iron is a hard material with high compressive strength.
2. Brittleness: It is a brittle material that lacks ductility and has low tensile strength.

Machining Process:
1. Cutting Tool: The cutting tool used in machining cast iron is typically made of high-speed steel or carbide, which are harder than the workpiece material.
2. Cutting Speed: The cutting speed for machining cast iron is generally low to prevent excessive heat generation.
3. Cutting Forces: Machining generates cutting forces that act on the workpiece material, causing deformation and removal of material in the form of chips.
4. Tool-Chip Interface: The tool-chip interface experiences high contact pressures and friction during machining, leading to chip formation.

Discontinuous Chips:
1. When machining cast iron, the chips produced are typically discontinuous in nature.
2. This means that the chips are not continuous and are fragmented into smaller pieces.
3. The discontinuous chips are formed due to the brittle nature of cast iron and the high compressive forces acting on the workpiece material during machining.
4. As the cutting tool removes material from the workpiece, cracks and fractures occur in the cast iron, resulting in the formation of fragmented chips.
5. These chips are characterized by irregular shapes and sizes, and they break away from the workpiece in a discontinuous manner.

Advantages of Discontinuous Chips:
1. Discontinuous chips are easier to handle and remove from the machining zone compared to continuous chips.
2. They reduce the risk of chip entanglement and chip jamming, which can lead to tool breakage and poor surface finish.
3. Discontinuous chips also help in the efficient evacuation of chips from the cutting zone, preventing chip recutting and heat buildup.

In conclusion, when machining a hard and brittle metal like cast iron, the type of chips produced is discontinuous chips. These chips are formed due to the brittle nature of cast iron and the high compressive forces acting on the workpiece material during machining. Discontinuous chips offer advantages such as ease of handling, reduced risk of chip entanglement, and efficient chip evacuation.