Answer:

Introduction:
Deep hole drilling is a machining operation that involves drilling holes with a high aspect ratio, i.e., a high depth-to-diameter ratio. Electrical Discharge Machining (EDM) is a common method used for deep hole drilling of small diameters, such as 0.2 mm.

Tool Material Selection:
When selecting the tool material for deep hole drilling with EDM, several factors need to be considered, such as electrical conductivity, melting point, and wear resistance. These factors play a crucial role in the performance and effectiveness of the drilling process.

Copper Wire:
- Copper wire is a commonly used material in EDM due to its high electrical conductivity.
- However, when it comes to deep hole drilling of small diameters, copper wire may not be the ideal choice.
- Copper has a relatively low melting point, and the high temperatures generated during the EDM process can cause the wire to melt or break easily.
- Additionally, copper wire may not provide sufficient wear resistance for drilling small diameter holes.

Brass Wire:
- Brass wire is another material used in EDM due to its electrical conductivity and relatively high melting point compared to copper.
- However, brass wire may not be the best option for deep hole drilling of small diameters.
- While it offers improved wear resistance compared to copper, it may still have limitations in drilling very small diameter holes.

Tungsten Carbide:
- Tungsten carbide is a popular tool material for deep hole drilling of small diameters in EDM.
- It has a high melting point, excellent wear resistance, and good electrical conductivity.
- Tungsten carbide can withstand the high temperatures and stresses generated during the EDM process, making it suitable for deep hole drilling of small diameters.
- It also offers a longer tool life, which is important for cost-effective drilling operations.

Conclusion:
In the context of deep hole drilling of small diameter holes (0.2 mm) using EDM, the most suitable tool material is tungsten wire. It provides the necessary properties of high melting point, good electrical conductivity, and excellent wear resistance. Tungsten wire ensures the stability and effectiveness of the drilling process, resulting in accurate and efficient hole drilling.