I have a customer asking me can i make graphite molds for the purpose of metal casting. I watched Winston’s video on the subject and it looks like from a machining standpoint, it machines quite well. My concern is the safety side of things as i didn’t realize it was quite so toxic too breath as well as harmfull to the cnc if dust gets places it shouldn’t. For dust collection, i use my sweepy hooked up to my dewalt steathsonic shop vac. Think thats adequate for the task, or will i need to upgrade my dust collection to safety mill graphite?
I would be concerned with the fine particles that escape the Sweepy.
If the surface is irregular in the Z axis, the Sweepy becomes less effective.
Where a good mask.
Also be very careful about the dust getting into your electronics and router it is conductive.The dense graphite will machine very well.used to have crucibles machined out of a solid block of graphite.These were broken electrodes from a EAF furnace.
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2 things I think are important to mention:
- When “dust” escapes Sweepy containment and lands on your table, that’s generally fine. Big particles have more momentum and will fly further, but they settle quickly. It’s the stuff you can’t see that should scare you. In most cases, a strong vacuum should do a decent job of corralling those. Never hurts to wear a mask on top of that though.
- If you were going to do this kind of work a lot, I would strongly suggest getting a HEPA-rated vacuum or dust collector. The Stealthsonic does not come equipped as such. They do sell a HEPA filter you stick onto the motor, but according to Reddit (take that with a grain of salt) you usually want a HEPA bag + filter for the best particulate protection. And I don’t believe the Stealthsonic line has HEPA rated bags available. You can probably get a bag from a different manufacturer, but if Dewalt didn’t design for this use case, you might see a reduction in suction.
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I agree that pretty much 100% of the fine/microscopic particulate would be sucked up via the Sweepy - it just doesn’t have the momentum to get very far from the spindle before the airstream sucks it up.
But this is definitely a situation in which having the CNC inside an enclosed cabinet would pretty much be mandatory. With the vac running, door closed & a controlled cabinet air-inlet, particles should not be able to make their way out except via the dust collection hose. Plus you can leave the vac on after cutting is finished just to ensure the air is clear.
Shop vac bags are pretty forgiving in that they do not need to be made specific for a model or brand - as long as the opening fits well over the hose air inlet & the bag is big enough not to fall off the air-inlet during operation.
Alternatively to trying to filter all the particulate from the air, OP could get a different vac which has an exhaust port to direct the airflow to the outside.
One of the downsides of the Stealthsonic is the lack of an exhaust port.
I appreciate everyone’s advice on this. Im not looking to mill lots of graphite right now so hopefully ill be ok with a mask and current setup. If its something i end up wanting to mill more of ill definitely look into either a new vac a little better suited for the task, or maybe even a enclosure if need be.
For the benefit of folks searching later, one solution not yet mentioned is flooding the work piece with oil.
One could make a shallow tub and fill it with some kind of oil (I’ve used vegetable oil since it’s non-toxic, cheap, and easy to get by the gallon) then submerge the work in the oil and begin cutting. It’s a fine way to keep the dust captured.
This method seems to be more common in pcb milling and can benefit from some custom jigs. If you’re just doing a one off…any kind of dam will work. Even a wall of hot melt glue gets the job done.
There’s plenty more to do if you want to make this a common part of a workflow, like circulating the oil with a peristaltic pump and such.
Might not apply to this particular situation, just wanted to mention it for folks who search later on 
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