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Machining magnesium


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Heavier finish passes.  You don't want thin chips.  Like Ron said, no dull tools.  Don't leave machine unattended.  Make sure you're not piling up chips inside the machine to mitigate issues should a fire start.  Water based coolant seems to oxidize the xxxx out of it.  Keep that in mind.  Preferrable to run straight oil.  If this is a machine that you run water based coolant in you'll destroy the coolant pretty quickly as the magnesium causes the hardness to skyrocket and the emulsifiers decide to go home (coolant splits.)  Other than that can't think of much.  I've machined a fair bit of it without issue.

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12 hours ago, #Rekd™ said:

You need a fire extinguisher for metals…they are very expensive. 

I think they are called halon fire extinguishers

also keep buckets of sand near by

rigorous chip control is required. clean the chips out constantly.

fine stringers are particularly dangerous.  

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We used to light up a handful of chips on the cement loading dock.

It gets the cement so hot it explodes leaving golf ball sized divots in the cement.

That's not real bright from a safety standpoint, but it was tons of fun.

There's lots of video on youTube of machine tools burned out by magnesium fires.

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As stated before, it will destroy any water soluble coolant, causing it to separate and become worthless. Plan on draining your tank & putting new coolant in every couple of weeks. There are some makes of coolant which supposedly tolerates the magnesium better, but I have yet to try. We have a reoccurring job once a year that runs for about a month, we add in a couple of days of cleaning and a new drum of coolant into the cost of the job. You gotta get all the magnesium out of the machine or you will be fighting coolant issues till you do.

The fire hazard is a real thing. One of the few jobs in the shop where we do not run lights out.

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I've only ever run it dry or with cutting oil and NEVER unattended.

If at all possible I highly suggest cutting oil as opposed to coolant. Cutting it with water-based coolant creates hydrogen gas which can be explosive in enclosed areas.

Class D Fire extinguisher and sand on hand FTW




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There are companies that make fire suppression systems for machine tools.

They are enclosed systems with  robust ventilation, smoke and heat detectors. 

and the capacity to close all the vents and flood the enclosure with halon.

I've seen video of them before.. I'll bet they are not cheap.

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Seems like everyone already talked about the fire dangers...

My dumbass did an experiment once, was only funny after I was done using the  extinguisher.  You may think its exaggeration, its not.  Make sure you keep the parts cool, and specially the chips.  And do not, I repeat, do not "try to see if its true that the chips catch fire"...they do.  Afte that first time on the mill I had a to do a couple of jobs on a lathe.  We cleaned the lathe out of the MAG as soon as the job was done, and not a minute later.

As far as machining it, it machines a lot like aluminum, even nicer.  I do remember the chips being very small, that may have been the tools I was using though.

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If you machine refractory metals, or Mag, Ti, Inconel, etc., I'd recommend looking into these guys. Their Metal Working Fluid (oil) has shown great performance in some very difficult materials for our government customers. I have no commercial affiliation or business interests with these guys, Phillips does not represent them or warranty their products, and these statements are my own. I just like their products and have heard good things from some guys I trust. But if you do call, tell Dave I gave you his contact!



Dave Antonuccio  |  Business Development Director

Mobile:   (828) 384-6541


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20 hours ago, gcode said:

Just take them out back and light them up!

They'll be gone in no time .

If you do this > you'll want to alert the Fire Department beforehand, and DO NOT do this at night. Ask me how I know. :ph34r:Something, something, 2nd shift, something, something, bored machinists, I think you get the picture.

And, I would not do this in California, Massachusetts, and/or any states with strict environmental protection laws, because if the wrong agencies catch wind (maybe literally, lol), that could be bad.

Also, if you should happen to be playing around, and lighting Ti or Mag chips on fire, the light is as bright as a welding arc. Save your sight! Don't look unless you've got the proper welding glasses/shield to protect your eyes. And again, doing this at night will absolutely alert the entire neighborhood to a bright white fiery light source, and this will attract all the wrong attention. :whistle:

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8 hours ago, cncappsjames said:

Bored machinists on night shift and magnesium. Sounds terrible. What's the address? Asking for a friend. 


Kirkland, WA. Big Okuma shop. Tier-1 Boing Subcontractor for many years...

If you know it, please don't say it. Lol.

Let's just say, it can be very easy to underestimate the amount of Mag. chips in a 55-gallon drum. Ours was maybe 20% full. Maybe. And that was good for 20 minutes of burn. Good thing the ignition was determined to be accidental, from an untrained employee putting hot chips in the wrong barrel... :whistle:

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