Tips for machining graphite
Graphite presents machinists and CNC operators with some unique challenges. Graphite is a softer material than steel and has some of the same characteristics as Aluminum for machining and fabricating. There are some important characteristics that are associated with machining Graphite that should be kept in mind. As a form of Carbon, Graphite is a very common mineral and is used in many industries including aerospace, construction, energy, and the military. Graphite is found in everything from #2 pencils to the diamonds in wedding rings and that covers the full range of hardness. It’s important to understand the make-up and characteristics of the type of Graphite used in the workpieces being machined.
Soft to machine, but hard on tools
One of the important things to remember about Graphite is that despite its softer makeup, the material wears out tool edges faster than steel. The abrasive qualities Graphite incorporates into its molecular structure make it extremely tough on tool edges. It is recommended that when working with Graphite workpieces, machinists use the following guidelines:
- Slow Speed – The higher the feed rate the more opportunity there is for chipping and fracturing. Carbon-based materials can handle higher pressure and higher heat but can be easily damaged by high-speed cutting heads moving too quickly across the surface.
- Lighter Cuts – Removing less material per cut will help increase tool longevity as well as decrease potential damage to the workpiece surface from fractures and breaks caused by vibration or tool chatter.
- Good Tools – Most machinists and CNC operators recommend using Chemical Vapor Deposition (CVD) Diamond-Coated tools as their increased diamond content will help resist the abrasive textures in Graphite. The cost for CVD Diamond-coated tools is higher than for other specialty-coated cutting heads, but the added life more than offsets the additional cost of replacing lower-grade tools much more often.
- No Coolant – Graphite doesn’t put off chips like most materials, it puts off fine dust particles. These particles can affect computer circuitry, environmental safety, and many other operating conditions. Coolant combined with Graphite dust produces an abrasive slurry that is hard to clean and can seriously affect machine functionality.
- Vacuum Up – Clearing Graphite dust can be accomplished using vacuums and air pressure controls. Dust can be filtered out of the ambient air, however, machine operators should wear protective breathing equipment. Removing the Graphite dust from the environment will reduce potential problems with dust build-up on sensitive parts and CNC machine electrical assemblies.
Once a machinist understands the nature and characteristics of working with Graphite materials, it becomes much easier to operate and maintain machine tools. The abrasiveness of Graphite, combined with the softer surface structure, and dust-producing off-put, make machining Graphite a challenge, unlike other materials. While caution should be used when it comes to tool cutting feed rates and cut depths, Graphite can be machined and fabricated with extreme accuracy. Quality tools contribute to enhanced tool life and with proper environmental precautions, machining Graphite can become routine.