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Machining magnesium

laminar-flow

Stainless
Joined
Jan 26, 2003
Location
Pacific Northwest
What kind of issues would one encounter when machining magnesium?

I know about the flammability, which should not be an issue since the parts are so small, <.700" x .400".

Not sure of the alloy yet, but probably something with high yield, not cast.
 
Your part isn't the problem. The fine finishing chips are. Keep things clean and be cautious and you should be alright. I'd keep a fire extinguisher of the correct rating nearby just for safety.

Good housekeeping is your friend when machining Mag.
 
fire hazzard

As long as you use a lot of juice and keep the tank topped up you should be fine. I worked at a shop a long time age and an operator did not check the coolant level in the tank. the tool ran dry halfway through the cut and needless to say there was quite a light show.
Luckily there was a extinguisher nearby and it was put out before any damage was done to anything but his ego!
Be sure to keep the chip pan clean!
 
I cant speak to your feeds and speeds question but I know of a guy that was facing some magnesium that had a fire issue. He was blowing off his machine and somehow manged to blow a chip into an uncovered wall socket. Somehow the chip or chips contacted two leads and started a fire in a small pile of chips.
 
RE: Machining Mag

It machines pretty similar to Aluminum. Pretty good advice so far, regarding housekeeping and the light cuts/chips being the primary issue as far as fire hazard. Water Soluble coolants can be problematic with regards to staining and corrosion issues, especially where the mag is in contact with other metals, clamps, aluminum subplates etc. If you are doing much volume it would probably be a good idea to look into a magnesium specific coolant to control those issues.
 
It machines pretty similar to Aluminum. Pretty good advice so far, regarding housekeeping and the light cuts/chips being the primary issue as far as fire hazard. Water Soluble coolants can be problematic with regards to staining and corrosion issues, especially where the mag is in contact with other metals, clamps, aluminum subplates etc. If you are doing much volume it would probably be a good idea to look into a magnesium specific coolant to control those issues.

Chobyn is right on the money based on my experience. We did a few weeks worth of magnesium last fall, and it raised hell with our coolant (Hangsterfer S506CF). The chips naturally all wanted to float on top of the coolant, and within just a few days, the coolant was really washed out--adding more concentrate than normal just didn't seem to help much. After the job was done, we had to completely clean the machine sump to keep the residual mag from continuing to dilute our coolant. It's something to keep in mind when quoting I guess!

It's my understanding that most shops that do a lot of mag use specialty coolants or just run cutting oil instead.

It wasn't bad to machine, though. We had a little trouble tapping a few parts, but we got that worked out pretty quickly.
 
I had to bore and broach a Magnalloy motor coupling Monday. It was magnesium there is a lot of info on Magnalloy's website on feeds and speeds and even how to put out the fire if your day didn't go so well. I thought it machined easy. The thing they preached was don't make fine dust by using fast feeds. At my job we use lance rods to cut cobbled copper and brass off our rolling mill when it crashes 3" thick copper strip The lance rods are a thin steel tube about 8 feet long filled with magnesium rods and fit into a holder supplied to an oxygen bottle You light the end of the rod off a cutting torch then open the oxygen valve and watch the sparks fly it keeps melting the steel tube back as it burns.
 
you can run mag at similar speeds/feeds like aluminum. Many people go "slow" because of the fire thing but unless you're in the habit of machining into vises, jaws, clamp screws and things like that, the mag is no big deal. You can cut it dry for Christ's sake...

I think I've had more titanium fires than mag fires......

But a few key points have been brought up here..... Coolant types will play with the cosmetics (staining and such). But for sure.... Get a good fire containment and supression system rated for mag (or other self sustaining fire types).
A good coolant bath doesn't stop or prevent a mag fire (although it certainly helps to keep the chips away)...... Mag fires can start completely submerged.... just don't try to machine off the fixture screws or hard jaws at 10000 RPMs....
 








 
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