Question

A through hole of 8 mm diameter is to be drilled in a 30 mm thick mild steel plate. Which one of the following processes is the most appropriate to achieve high dimensional accuracy with less processing time?

• A. Conventional drilling using a carbide drill bit
• B. Die sinking EDM using a copper electrode
• C. ECM using a copper electrode
• D. Plasma arc machining

Hint:

For simple hole-making tasks, conventional drilling with carbide drill bits is often the most efficient and accurate process. More specialized methods like EDM and ECM are typically used for more complex or hard-to-machine materials.

Answer 1

The Correct Option is A

The problem involves drilling a through hole of 8 mm diameter in a 30 mm thick mild steel plate, and we need to choose the process that provides high dimensional accuracy with less processing time. Let’s examine the options:
- Option (A): Conventional drilling using a carbide drill bit is a commonly used method for drilling holes in steel. It provides good dimensional accuracy and is efficient in terms of processing time. Carbide drill bits are ideal for working with mild steel and can provide good hole quality with relatively fast cycle times.
- Option (B): Die sinking EDM (Electrical Discharge Machining) using a copper electrode is more suitable for precision machining of complex shapes, particularly in hard materials. However, it tends to be slower than conventional drilling and is not ideal for achieving high dimensional accuracy in thick materials for a simple hole.
- Option (C): Electrochemical machining (ECM) using a copper electrode is used for materials that are difficult to machine, such as superalloys or hardened steels. While ECM provides high accuracy, it is generally slower and more complex than conventional drilling for a simple hole in mild steel.
- Option (D): Plasma arc machining is typically used for cutting thick materials, especially metals. While it can quickly remove material, it is not suitable for achieving the high dimensional accuracy required for drilling small holes like 8 mm in mild steel.
Based on the need for high accuracy and speed, conventional drilling using a carbide drill bit (Option A) is the most appropriate process. This process provides a good balance between dimensional accuracy and processing time for the given application.