Rough edge cutting aluminum, advice?

DanO - Thank you! Wow lots of great info here :slight_smile:

Same situation here, I’m making aluminum sheetmetal stuff for our robot.

Do you find the vacuum is enough to remove chips? You use the normal setup with the vacuum sucking up the chips?
I haven’t dared try this yet, I am still a bit nervous cutting aluminum, and it’s nice being able to see the cutter. I have rigged a reversed vacuum in the boot so that it is blowing at the cutter.

Also, those speeds and feeds are just about what we came to when testing stuff (although we do 22k rpm) which is good to hear!

Why 6061 for heat sink? 6061 is a strong alloy, was once known as an aircraft skin alloy. maybe a softer alloy such as 1100 O temper would work better as a heat sink if strength is not a factor.

Softer is worse as far as machining goes. Most alloys gum up and anarchy ensues. 6061 was specifically alloyed to be as machineable as possible.


I have an XXL w/ HDZ and 2.2kw er 20 spindle. Used for roughing an O-flute 1/4"(LMT Onsrud) at 19k and 60 IPM at .030" DOC. I misted with some wd40 silicon spray, pretty messy, but heat is a killer. Finished with a 2-flute 1/8" and a 15deg tapered ball. Could not hear the cutter, only sound of vac. 6061AL. 2 or 3 fluter will not allow chip evacuation without flood coolant or high pressure air etc. I agree with statements that you have to feed aggressively enough to cut the material, otherwise you are plowing. Less time in cut equals less heat.


I got my air / mister setup. Going to try it with just air, but I can easily add water or alcohol to it.

Quick questions if I do:

  1. I have Isopropyl Alcohol, but Denatured Alcohol - does the type matter? I see references to both on here and elsewhere.
  2. Is a 50/50 mix of Alcohol and Water good?
  3. Likelihood of fire? Lol
  4. If I also have a wet/dry vac sucking up some bits with the Alcohol in the air - any risk there?

Master @Vince.Fab uses a 50/50 mix of water and alcohol and he says that’s safe:

With so little being sprayed, it will evaporate rather quickly anyway


I use my thumbnail to adjust the mist. Turn on the air, then start to ease up the coolant until it just starts to form tiny little droplets on your thumbnail (Or a piece of dry paper works too.)
My cheap system tends to ‘drip’, intermittent puffs of coolant every ~half second rather than a constant mist. If I position my eye so there is a dark background I can see the puffs.
I put a drop of blue loctite on the coolant screw then wiped most of it off to keep it from vibrating & moving.


Sorry Madelyn about taking so long to reply…
Awesome to hear you are also doing stuff for robotics! My team is FTC #10273

The end mill tends to throw chips out of the groove but they’ll settle back in if there isn’t a vacuum. With the vacuum they just get sucked away. I use a PwnCNC v2 dust shoe with a Fein Turbo I vacuum. With this dust shoe the vac connection is on the backside so there is reasonably good view of the cutter and if you take off the front part of the dust shoe there is really good view and still acceptable cleanup of chips.

It doesn’t really matter what type of alcohol. Denatured is generally cheaper which is why I use it. Isopropyl is literally sold to be rubbed on the skin so it has less toxicity than denatured (which is mixture of ethanol and methanol.) But denatured is not really that toxic either - just don’t go drinking it.

If Vince says 50/50 mix - go with what he says. I use just straight denatured as it’s quick and easy and does the job.

Yes - alcohol can burn. But you have to get quite a bit of it. I did some experiments when I was thinking about the risk of it. When I pour alcohol on the plate I can sometimes get it to start burning when I use a lighter. But it aint easy. I have sprayed it into the air both with my mister and with a sprayer bottle - I can’t get that to ignite even using a propane torch. (I was kind of hoping to make a nice fireball but no luck).

When using it with the vacuum you don’t even notice the odor in the air when walking into the room. The amount of alcohol to amount of air just dilutes it so much there isn’t any problem.