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YankeeMetallic
01-30-2006, 03:32 PM
I picked up a job today where I have to cut, mill, and tap small graphite slabs (3/8 thick X 1" X 2" up to 3" X 5")
Does anyone have experience machining graphite. Are there potential hazards, warnings etc. How does it wear on your cutting tools, clamping problems, tapping problems, etc?
Thank you in advance.

Evan
01-30-2006, 03:39 PM
Incredible horrible nasty filth problems will be the worst side effect. You need to rig a vacuum with a special bag rated for flammable dust in the micron size range such as is used to vacuum up copier toner.

fixxit
01-30-2006, 03:44 PM
The stuff is really messy and brittle.

Here is the MSDS data:
Inhalation:
May cause irritation to the respiratory tract. Symptoms may include coughing and shortness of breath. May produce black sputum, decreased pulmonary function and lung fibrosis.
Ingestion:
Not expected to be a health hazard via ingestion. May cause irritation to the gastrointestinal tract. Symptoms may include nausea, vomiting and diarrhea.
Skin Contact:
May cause mild irritation and redness.
Eye Contact:
May cause mild irritation, possible reddening.
Chronic Exposure:
Chronic inhalation exposure to natural graphite is associated with the development of pneumoconiosis, a disease of the lungs.

Aggravation of Pre-existing Conditions:
Persons with pre-existing respiratory or cardiopulmonary problems may be more susceptible to the effects of this substance.

------------------
457863656C73696F7220212000

[This message has been edited by fixxit (edited 01-30-2006).]

Evan
01-30-2006, 03:49 PM
Don't forget that it is also a conductor. If it gets in your electronics or motors it can trash them. The dust is highly flammable and can cause a dust explosion. You should use a properly rated vacuum pickup right at the work.

SGW
01-30-2006, 03:58 PM
Repeat all that stuff about "mess" ...

It machines really easily, not abrasive (based on the little I've done). Kind of fragile, so you need to be gentle on the clamping, but since it cuts pretty easily that tends not be a huge problem.

x39
01-30-2006, 05:19 PM
We machined quite a bit of it in a shop I once worked at. We used a flood of water based coolant, which completely eliminated the dust factor. The parts were then run through an oven to dry them out.

Mcruff
01-30-2006, 05:20 PM
What grade of graphite. There are several grades, the cost cutter grades are very porous and brittle. The EDM #2 and 3 and the Poco grades are very easy to machine and not brittle all in thicker parts like you are talking about, the copper impregnated is even better. The stuff is easy to tap. As far as the dust you would have to machine quite a bit of it. Explosion proof, you gotta be kidding me, I have literally machined 1000's of pounds of this crap over the last 20 some years and have seen it glow red from rough grinding on it and couldn't start a fire. If it will burn in dust form I've never seen any of my Torit dust collectors have a problem and I have used
a bunch Craftsmen shop vacs on it over the years on mills where we did not have vacuum hooked up and never had a problem. Graphite is basically inert. 99% of the people will not have any reaction to it at all in any way shape or form. You can use a small dust mask for the purpose you describe and a shop vac will work just fine to suck up the dust in the small amount of parts you are talking about. It is messy but can be controlled with a shop vac very easy!!!!!!!!!!

[This message has been edited by Mcruff (edited 01-30-2006).]

Evan
01-30-2006, 05:46 PM
From graphite MSDS:


<font face="Verdana, Arial" size="2">
Fire/Explosion Hazards:  Emits toxic fumes under fire conditions. This material, like most materials in powder form, is capable of creating a dust explosion.</font>

http://www.hummelcroton.com/msds/grph_m.html

japcas
01-30-2006, 06:17 PM
I agree with X39. In the shop where I work we cut it occasionally and we flood it with coolant. It machines good and you don't have to run it fast to get a good finish so you don't have to worry about throwing the coolant all over the place. Just a small stream over the cut is all it takes to keep down the dust.

Mcruff
01-30-2006, 06:24 PM
Yea but you missed the part that describes it as non flammable and capable of being explosive under specific conditions only. In any condition that you would find in a normal shop consider it non explosive.

<font face="Verdana, Arial" size="2"># Flammability:  Non-Flamable
# Flash Points:  Not Applicable
# Auto-Ignition:  Not Applicable
# Flammable Limits:  Not Applicable
# Extinguishing Media:  Water Spray
# Fire Fighting Procedure:  Spray with water
# Fire/Explosion Hazards:  Emits toxic fumes under fire conditions. This material, like most materials in powder form, is capable of creating a dust explosion</font>


[This message has been edited by Mcruff (edited 01-30-2006).]

Evan
01-30-2006, 06:35 PM
People can go for years handling materials that are capable of causing a dust explosion and never see it happen. I spent 23 years working with copier toner, cleaning and vacuuming etc. It never exploded. I took an extra bottle of it home one day to see if it really would explode.

I tossed a large tablespoon of it over a small campfire out in in the yard. HOLY ****. BOOM!!!

Wheat isn't rated as flammable either but the dust blows up just fine.

More important with the graphite is the ability to short out electronics. That can really cause trouble, especially around computers.

Fasttrack
01-30-2006, 06:51 PM
Graphite is just a particular crystaline structure of carbon. Being carbon it is indeed flammable, to the same extent that coal dust is flammable. Not likely to happen from a little spark and would have to be in the correct mixture. Certainly not likely to find enough dust homogenously mixed with air, especially with the operartions described, to explode. nevertheless, it IS combustible.

lynnl
01-30-2006, 08:23 PM
Ok, now it's starting to make sense. ...
...Mary taking a shower over at Tinkerer's house. Then come the weekend she's over at Evan's taking a shower. (see "water heater timers" thread). That had me wondering!

Now we have the issue of machining graphite, a dirty, messy proposition for sure. Certain to entail a need for bathing.

I think I've figured it out ...a sordid threesome affair involving Tinkerer, Mary, and Evan. All out in the shop nude, machining graphite, ..and who knows what other activities...

And to think.. this a HOME shop forum. tsk..tsk.

Evan
01-30-2006, 10:44 PM
Mary only lives a short walk from our house. She has been over on a regular basis, usually on the weekend. She is one of the few people that has actually seen my completely exposed....

By the way, I don't think she is Tinkerer's type. She is 60 and the last time she had a good look at my... Well, lets just say that barium enemas are no fun. She is a radiologist. http://bbs.homeshopmachinist.net//biggrin.gif

lathehand
02-03-2006, 02:47 PM
One thing to look out for is chipping of corners. You can take huge cuts with a fly cutter but you will break chunks out of the corner when the cutter exits the 'trode material ( I am assumeing you are making EDM electrode blanks).We wipe our lathe dry of oil when we machine graphite so as not to create a slurry that would get in everywhere. Mills are not so bad,but I will wipe the quill off before retracting.

YankeeMetallic
02-04-2006, 05:56 PM
<font face="Verdana, Arial" size="2">Originally posted by lathehand:
( I am assumeing you are making EDM electrode blanks)</font>
I don't know the grade of graphite because the customer is supplying it. It is not cunducting electricity as a final product so the grade probably won't matter. I can't give up what it is because the parts are a specialized item for a specialized industry. Yes it is messy but easily controlled with slow spindle speeds and feeds and a shop vac mouted right next to the cutter. It is also rather abrasive on the cutters. It's kind of wierd to work with. Thank you for your input.