EDM tool (electrode) materials: In electro-discharge machining, which of the following are commonly used electrode materials?

Introduction / Context:
Electro-discharge machining (EDM) removes material by controlled spark erosion between a shaped electrode and the workpiece. Electrode material selection affects wear rate, machinability of the electrode itself, electrical/thermal properties, and ability to hold fine detail.

Given Data / Assumptions:

• Sinker EDM context.
• Work materials may be hardened steels, superalloys, or carbides.
• Normal dielectric fluids and power settings.

Concept / Approach:
Common electrodes include copper (excellent conductivity and finish), brass (cost-effective, good for small holes and fine details), copper–tungsten (high temperature strength and good wear resistance), and graphite (very common for complex cavities with good wear behavior). The best choice balances electrode wear, detail fidelity, and surface finish targets.

Step-by-Step Solution:

Verification / Alternative check:
EDM vendor catalogs consistently offer brass tubes (for EDM drilling), oxygen-free copper plates/rods, and Cu–W grades for wear-resistant electrodes, alongside many graphite grades.

Why Other Options Are Wrong:
“Graphite only” is incorrect; metals listed are widely used. Any single choice would be incomplete, hence “all of these” is correct.

Common Pitfalls:
Ignoring electrode wear compensation in toolpathing; selecting copper in delicate thin-ribs where graphite may be stiffer/lighter; overlooking flushing design that interacts with material choice.

Final Answer:
all of these