[davidsutton]

I have been asked if it is possible to machine graphite - in order to make a mold for casting glass into - aparently the surface of the set cast glass clouds less if it is molded into graphite rather than plaster.
Does anybody have any idea what this involves - is graphite readily available? do people cut pure graphite or is it a compund - does it need cooling fluid, etc..
the question is just speculative so nobody please bust a gut... just finding out if anyone else has done anything similar.

[Andre' B]

Do some web searches for EDM electrodes, you will find graphite all over the place.
Just one example.
http://www.graphitestore.com/stores.asp/cat_id/12


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.

[davidsutton]

thanks for the prompt reply, i checked out the link - graphite was less expensive than i thought it would be..
in terms of size though - do you think 5 inch x 5 inch x 3 inch block is obtainable - i only looked at the web link you suggested so far.. i have not done a wider web search yet

anyways thanks very much for your help
best regards
ds

[Andre' B]

That size is easy. The places that sell it to the end users get it in blocks the size of small cars and cut it up.

Just seen you are in the UK, I do know that EDM shops in Europe tend to use more copper for electrodes then we do in the US, but graphite should still be available.

[dang]

Does graphite need to be milled at high speeds?

[dang]

Apparently it doesn't need to be machined at high speeds. Feeds should, of course be proportional for best results.
The big issue as I understand it now is dust collection. The dust starts at the cutting tool and travels in the opposite direction of that tool. Vacuum solutions become more difficult as the part's complexity grows. The most modern and effective way to capture the dust is with coolant, not that you'd need that coolant for anything else.
Rather than quote the article, I'll just link to it.

http://findarticles.com/p/articles/m...67/ai_16339352

Like any good hall monitor would, I looked up disposal as well. The EPA and OSHA don't consider Graphite Dust to be dangerous so long as it's not floating around in the air or is caked to the workshop walls. I can't find any disposal regulations at all. Can anyone else find any rules or regs on this?

[DJPLAST]

Here is another source for graphite:
http://www.poco.com/Home/tabid/36/Default.aspx

[keithorr]

Graphite is just a material. It takes the thermal shock of molten glass but doesn't necessarily produce a good finish by itself. It conducts heat too efficiently to allow the glass to set without the surface seizing up; called chill marks.
I machine graphite for glass molds. Not many glassmakers understand how to use them. Sounds like a good idea but often is an exercise in futility.

You don't really want graphite;"graphite" is just a word people use. You want carbon which is the physical state before the billet is cooked to the graphite phase. It has to do with the thermal conductivity aspect.

GraphiteStore.com doesn't have the best quality material. I use some of their offerings for inexpensive substrates.

Ed Skeels
www.keithorrblowpipes.com/molds.htm

[dang]

I'm thinking of machining high density or graphite specifically for Aluminum and Zamak molds. I've seen some nice chemical additives that make release a snap and improve the castings finish.
I also read that I'll have to use Diamond End Mills to cut the Graphite. Does it machine easily, or is it very difficult? Please illuminate me further.

[K&Y]

I'm thinking of machining high density or graphite specifically for Aluminum and Zamak molds. I've seen some nice chemical additives that make release a snap and improve the castings finish.
I also read that I'll have to use Diamond End Mills to cut the Graphite. Does it machine easily, or is it very difficult? Please illuminate me further.

Your best bet as far as milling Graphite would be to use PCD (Polycrystalline Diamond) tipped endmills. They are widely used in the aerospace industry already.

[svenakela]

I was milling pretty much graphite before, EDM probes. We didn't use any special mills as I remember, just standard TIN-coated HSS-mills and sometimes carbide mills.

Either keep the milling process under water or use vacuum, you can't even imagine how dusty it is.

[K&Y]

I was milling pretty much graphite before, EDM probes. We didn't use any special mills as I remember, just standard TIN-coated HSS-mills and sometimes carbide mills.

Either keep the milling process under water or use vacuum, you can't even imagine how dusty it is.

You can use coated carbide, but if you were to run a head to head performance test on both variations, you'd see the difference. I'll use the following as an example:

PCD-tipped countersinks, and non PCD-tipped countersinks, used in the aerospace industry. You'll see somewhere in the neighborhood of a 200-300% increase in tool life for the PCD-tipped countersink. Large companies such as "POCO Graphite" use PCD-tipped tooling in their graphite production process, just to give you an example. If tool life isn't a concern, then it won't matter. As far as evacuating the dust, there are several solutions out on the market if you are going to be milling. You are correct when you say that it's hard to imagine just how dusty it can get when machining graphite.

[dang]

I've settled on using Diamond Coated End Mills. Even though they're QUITE EXPENSIVE, I've read accounts that state that 4, maybe 5 Graphite projects can be eaked out of diamond end mills. This is where POSSIBLY only 1 out of conventional end mills, maybe not even that.

Here I thought that Graphite would be easy to machine. Like butter. It's tougher than I thought. Guess I was wrong. At least I'm accustomed to it.


Worse than that, I found like 400 lbs of EDM Graphite for FREE on Craigslist! By the time I called it was all gone. Oooooooh the agony.

Where dust is concerned, I'm thinking of building an enclosure. I'll pump coolant in to catch the dust as it emerges from behind the cutting tool. I've seen accounts of this working as well.

Thanks for all the input.

My new question is whether or not I can cut Graphite on a CNC'd Sieg X2 Mill. The mill runs under 4000 rpm's. I don't know if that'll be an issue or not.
I do know that if it is possible, that it would kick serious butt!

[K&Y]

I've settled on using Diamond Coated End Mills. Even though they're QUITE EXPENSIVE, I've read accounts that state that 4, maybe 5 Graphite projects can be eaked out of diamond end mills. This is where POSSIBLY only 1 out of conventional end mills, maybe not even that.

Here I thought that Graphite would be easy to machine. Like butter. It's tougher than I thought. Guess I was wrong. At least I'm accustomed to it.


Worse than that, I found like 400 lbs of EDM Graphite for FREE on Craigslist! By the time I called it was all gone. Oooooooh the agony.

Where dust is concerned, I'm thinking of building an enclosure. I'll pump coolant in to catch the dust as it emerges from behind the cutting tool. I've seen accounts of this working as well.

Thanks for all the input.

My new question is whether or not I can cut Graphite on a CNC'd Sieg X2 Mill. The mill runs under 4000 rpm's. I don't know if that'll be an issue or not.
I do know that if it is possible, that it would kick serious butt!

Yep. diamond coated endmills will give you longer life, most definitely, but with the PCD alternative, you can re-lap the diamond when it's cutting edge has worn out, thus increasing tool life even further. I didn't know if you had a speed/feed rate chart to use as a reference, but I thought I'd post one up for you as per PCD usage. Hopefully, this will help.

[svenakela]

Here I thought that Graphite would be easy to machine. Like butter. It's tougher than I thought. Guess I was wrong. At least I'm accustomed to it.

It is easy to cut, but it will make the tools dull very fast.

[dang]

It is easy to cut, but it will make the tools dull very fast.

Thanks for clearing that up for me.

[rakker16mm]

At the risk of bumping an old thread... I am machining some graphite for a rocket by Team Phoenicia

[nomedia="http://www.youtube.com/watch?v=h7U20yCmgjw&feature=player_embedded"]YouTube - Engine for the Zephyr Aurora[/nomedia]

About 30 years ago at my first paying job as a machinist I had to cut graphite. The dust was awful and I had black goobers in my nose for the entire job run. My boss was this crotchety old guy from Czechoslovakia, a great machinist but not too big on the idea of dust masks or even safety glasses. I didn't stay long...

Anyway this time around I thought I would do things my way. I am using a wet/dry shopvac pulling through a water trap. Really it is a glorified hooka and it is very effective. Nearly all the dust is sitting at the bottom of the bucket as black sludge.

[awemawson]

I was suprised to see in an earlier post in this thread about the graphite dust being very abrasive. Powdered graphite is used as a lubricant so I wouldn't have expected that to be a problem - anyone know for sure as I will be machining EDM electrodes in the new year on my Beaver Partsmaster for use on my die sinker?

AWEM

[svenakela]

I was suprised to see in an earlier post in this thread about the graphite dust being very abrasive. Powdered graphite is used as a lubricant so I wouldn't have expected that to be a problem - anyone know for sure as I will be machining EDM electrodes in the new year on my Beaver Partsmaster for use on my die sinker?

AWEM

Read the thread again, there are several people with the knowledge that posted info about what you are asking for. That's the main reason for using high end mills.

Just because there is a lubricant powder made of graphite it doesn't destroy your end mill? Wrong assumption my friend.

[awemawson]

Not bothered about the end mill - they are expendable - it's the machine slides etc that I'm more concerned about.

There is a world of a differance between carbon and graphite despite them being chemically the same - after all diamond it carbon as well. Carbon used for the electrodes of a battery is usually very hard and brittle, wheras carbon brushes on motors are usually soft. It's that later form I use for EDM electrodes.

AWEM