Machining Graphite with Diamond Coated Tools
Graphite is a material that is relatively easy to machine, but it is very abrasive which makes it very hard on tungsten carbide. This makes it a perfect candidate to machine with diamond; in fact, diamond coated end mills last 12-20 times as long as tungsten carbide when machining graphite and sometimes even longer.
Diamond coated end mills have a very wide operating range from 200 to over 2000 surface feet per minute. This provides an opportunity for significant productivity increases.
You will see from the chart below that in machining graphite it is not necessary to have a "high speed" mill to derive benefits from diamond, but generally speaking the higher the speed the more the benefit. We usually suggest keeping the feeds and speeds the same as what you are currently using for comparison purposes, then increasing the speeds to realize productivity gains.
Recommended Parameters for Graphite Machining by End Mills