What RPM/Depth of cut?

[sp1nm0nkey]

I feel like I've been taking awful conservative cuts, and I'm wondering if I should step it up a notch. If i'm cutting 6061 aluminum on a bridgeport with a 2 flute carbide end mill, what spindle speed should I be running? How deep a cut can I take? Feed rates I think I'll be able to feel out, but if there's a certain setting on the autofeed dial that works nicely I'd appreciate that as well.

[BMackinnon]

What size of Endmill are you running ?
But Im going to assume since it is a bridgeport that you should be able to max out your spindle speed and feed once you find a depth of cut that works.

[sp1nm0nkey]

Say a half inch end mill.

[joecnc1234]

You should be able to run at or near top rpm and at least full cutter diameter depth and fast feed if you use a mister or air blast to clear the chips, with good workholding and lock your axis that is not moving. Joe

[davereagan]

The helix and coating on the endmill is critical, especially without flood coolant. I would mist it with that Trico vegetable oil that is ~$70 a gallon but uses only a couple of ounces a shift. TiCN, TiB2 or ZrN coatings are the best for aluminum. An endmill made especially for cutting alumimum will be the most free cutting and therefore generate the least heat and possibility of galling. If you are using a standard 30 degree general purpose endmill, the vibrations and galling will happen a lot sooner. Full speed on a standard variable speed (not J head) Bridgeport is 4200 rpm. With a 2 flute endmill, that's 8400 teeth per minute. Full blast on the feed is probably 35 inches per minute, which would still only be ~.004" per tooth, which is reasonable. If you can run a full diameter deep with a full diameter wide slot, that would be 1/2" x 1/2" x 35 inches per minute for a metal removal rate of 8.75 cubic inches per minute. That's probably right around 3 hp of power consumption depending on the cutter. To me, the biggest question would be the issue of galling the endmill, which is ugly. It takes a few minutes with a center punch and a hammer to delicately chip the aluminum away to save the endmill. If you can slot a full diameter deep at full feed, you'll spend more time sweeping up chips than making them. :<) If we could put this on a VMC with 20 hp, I could run an Imco Streaker endmill at 200 inches per minute at a full slot, 1 diameter deep. I have galled a few endmills pushing them in aluminum. Semi or Soluble oil based coolants work better. Any questions email davereagan@hotmail.com