Graphite is the material of choice for the majority of EDM electrodes produced today in the United States. Selecting the best grade of graphite for a particular application can be difficult if the differences between graphite grades are not understood.

Depending on the graphite grade selected and the application, the graphite can be the limiting or the key factor in achieving the desired results from the equipment.

There is a wide range of grades from a number of manufacturers to choose from. Each manufacturer uses different processing techniques, source materials and process controls, which mean the end product, will be quite different. Each manufacturer’s grades are designed for optimum performance for specific types of applications. To aid in material selection, each manufacturer publishes technical specifications on their material, but there are no standard test methods.

Since any grade of graphite looks similar to another grade, appearance is not part of the selection criteria. Each grade should be selected by its physical characteristics and properties. To make this process easier, various grades of graphite are grouped into six classifications that are segregated by average particle size. Only four of the six classifications are suitable for use as EDM electrodes. How the different grades rank within the classifications is an indicator of their performance potential.