[MageDK]

Hello all,

I am working on a project with a hobby CNC mill (Sainsmart 3018-prover) I've done a lot of good looking pieces in wood. I have basically used a variety of 2 flute straight edge bits and a few round end up cut bits but that is where my experience ends

Now I am looking for some direction to be able to start carving Carbon graphite. I want to cut some molds in the graphite that I can use for casting metal. None of the bits that I currently have would be good for this.

I have done a few tests, in wood of the mold. I just need some bits that will allow me to cut into graphite. What types of bits would you recommend for this?

I am looking for a few square end and round end mill bits. 1mm + 3mm

[awerby]

PCD-coated bits are usually recommended for solid graphite. But be careful to patrol the dust really well; it's conductive and if it infiltrates any electric or electronic equipment, really bad things can happen. You might investigate an alternative process; making your mold parts positive in metal and burning them into the graphite with EDM. There's probably a shop that can do that part for you fairly cheaply, and the advantage (besides not having to machine graphite) is that duplicate graphite molds are easy to make off the same patterns, once you've burnt up the ones you made.

[routalot]

I have encountered graphite moulds for use with composite materials and would want to be certain the the material selected would be safe at the melting point of the metal.A small test might be a smart move and if the planned cavity can be cut with 1mm to 3mm tools it probably isn't for a huge part.What would be a disaster would be to expend a lot of time machining a nice cavity and then finding that it catches fire.

[awerby]

He's talking about solid graphite, not graphite-fiber composite material. Solid graphite (like the stuff inside pencils) is pretty refractory stuff; it's used for molding hot glass and for crucibles that metals are melted in: https://www.ozgraphite.com/product.php?cid=28 Graphite fiber composites are bonded with organic resins, and they'll burn. When I mentioned "burning up" the molds, I was talking about erosion of fine details, not implying they'd catch on fire.

[patsm00re]

Actual results could vary depending on several factors. Link to Google