Graphite is a highly abrasive material, and tends to wear out cutters quickly. One of the greatest difficulties encountered when machining graphite is that cutter wear can reach unacceptable levels within the time required to machine a single, multi-featured electrode. As such, advanced tool coatings offer a significant benefit when producing graphite components.

TiAIN, or diamond-coated tooling, is highly recommended for production of tight tolerance graphite components because it helps to minimize wear and maintain part accuracy. Uncoated carbide tools can be used, but are best restricted to roughing and semi-finishing, when tool wear is less of a concern.

To help mitigate the effects of cutter wear, the use of tool measurement probes on the machine tool is highly recommended. Tool length measurement probes, preferably non-contract laser probes, are particularly helpful when it comes to validating the length and diameter of cutting tools and tracking their wear state. Non-contact probes are best because they allow the cutters to be measured while rotating. This enables runout to be taken into account as part of the measurement. Unlike metals, when graphite is machined, you don’t get a continuous chip that has sheared off the workpiece. Instead, a combination of crushing and flaking occurs. Flaking is undesirable, particularly when finishing, because it appears as chipping of the surface. Using cutter geometry with a negative rate angle can reduce the amount of flaking and provide a larger crushing zone. This generates a better overall surface finish. Because a continuous chip is not created, a chip breaker isn’t required on cutters used in graphite.