Machining Brass with CNC Equipment
Advice on lubrication and cooling when working with sheet brass on a CNC router. June 30, 2007
Question
I'm trying to machine large 1/8" sheet brass on our Anderson Stratos Pro. Anybody have ideas on cooling the piece?
Forum Responses
(CNC Forum)
From contributor A:
Increase the feed rate. Are you using proper tooling for this application? I also used an air nozzle on my Shoda, which helped cool the cutting tool. I have also milled aluminum dry with the right tool and occasional sprays of WD-40 to prevent the chips from reattaching back onto the cutting surface. I was just routing 3/4" aluminum the other day.
There are tools made specifically for dry applications. Talk to your tool supplier; they will know best practices when it comes to applications such as yours. You can also talk to the material manufacturers/suppliers. The one good thing about the metal industry is they have charts everywhere on calculating feeds and RPM for every ferrous and non-ferrous material. I still use the formulas from my college days for getting feeds, RPM and chip load.
From contributor R:
Be careful. We machined an 1/8" thick sheet of brass, and the shavings got drawn up into our spindle and jammed between the fingers around the bullet. It caused the machine to not be able to open the spindle, and we had to take it apart, clean, lubricate, and recalibrate it. I refuse to cut metal on my machine again.
From the original questioner:
I'm using some Onsrud bits recommended for cutting aluminum, 3/8" upcut 2 flute end mill. Think maybe a downcut would be better in terms of getting material away from the spindle? Downcut chips getting in the way a potential problem in brass?
From contributor I:
I have not tried this, but scroll saw guys will cut metal between thin sheets of plywood or hardboard. I wonder if this would keep the brass cooler… less heat in the chip since it would have sawdust around it all the time, or just cause a mess? Just thinking out loud.
For another idea, when I have to cut thick aluminum on our dry bandsaw, I run a thick bead of paste wax on top of the cut line. The heat from the cut melts it and keeps the chips from sticking to the blade. How about cutting a simple template and using it to show where to smear on some lube?
I don't like the idea of a down cut unless you can get rid of the chips instead of shoving them into a spoil board. How about a shop vac hose with a small nozzle for high velocity to pick up the chips?
From contributor S:
A downcut bit will be fine for this application because the material is only 1/8 thick. The chips will just shoot down the machined groove. I use a 5mm single flute downcut to cut 5/16 phenolic all day long with no issues. Suction will be more important here because brass is a lot heavier than wood chips and will be harder to suck up. Check with your bit supplier for speeds and feeds. The correct feed/speed will put most of the heat into the chip and not the bit.
