Do some web searches for EDM electrodes, you will find graphite all over the place.
Just one example.
You can use just carbide tools but there is tooling available just for graphite.
It basically turns to powder when you machine it, you will want to have a vacuum setup to keep down the dust.
That dust is very abrasive so you want to keep the machine as clean as possible.
No need for coolant but it does control the dust, the coolant then turns into a black mess the works great for lapping the machine ways and bearings. It will also soak into the graphite some and may affect the casting process.
Graphite comes in many grades, the more expensive stuff will give you a better finish.