Machining Cast Aluminum

[George_Race]

I went to buy a piece of 3/8 6061T6 today. My usual supplier did not have any but did have some very nice looking Alcoa Cast Aluminum, exactly .375 thick. The sales person assured me it would cut just like 6061T6.

Bought it, should not have! Using the same speed and rate as I do for 6061T6 it gums up the bit, and makes a terrible mess! Broke two carbide bits before giving up on the project.

Can someone tell me the speed and feed that I should be using vs. 6061T6?

Only trying to cut .015 depth per pass, 10,000 RPM, and 30 IPS. Works great in 6061T6, disaster in Cast Aluminum.

George

[davidh]

at that rpm i would think you would melt any aluminum that hit the tool . . . just sayin'

[KiddZimaHater]

WOW! 10,000 RPM?
My little lathe maxes out at 1500 RPM, and it cuts 6061 like a breeze.
You might want to lower your RPM, and use WD-40 as cutting fluid.
Works great for me.

[bborr01]

George,

It is difficcult, no impossible to figure out a proper rpm when you don't give the cutter diameter.

Also, 30 ips? That is 1800 ipm. No wonder you are breaking end mills. (bits?)

Brian

[Lew Hartswick]

I suspected "George" was trolling untill I checked his profile. Either he's
using almost microscopic cutters or "arithmetically challenged" ??? :-)
...lew...

[Toolguy]

I'm thinking he meant 30 IPM. The main problem is that cast alum. is soft and gummy compared to 6061. It needs a lot slower spindle speed than 10,000 RPM and either flood coolant or a good alum. cutting fluid.

[baldysm]

Seems like your biggest problem is the lack of coolant. 95% of what I do at work is aluminum, both 6061 and cast aluminum.

30 IPM is nothing for what I do. I'll go 6000 RPM, .5" depth of cut, and 60 IPM with a flood coolant designed primarily for aluminum, with a 3/4" roughing end mill for aluminum (not a corn cob).

Aluminum in general is gummy, cast aluminum is even more so. I don't cut 6061 and cast aluminum any different, but if I loose coolant for some reason, I'll be in trouble in a hurry with aluminum sticking in the flutes of the cutter.

[George_Race]

Lew, trolling, "arithmetically challenged", I don't get the connection with my question. Maybe I am "reading challenged" too!

Brian, I did mess up, it should have been IPM, not IPS.
Bit diameter is .0938 and is a 2 flute carbide end mill.

Unfortunately, my setup is such that I just cannot use cutting fluid. It would really be messy, so I do everything dry.

I did end up being able to mill it, using 5000 RPM, .005 cut depth per pass, 5 IPM. Chips were very find, almost powder like in size, no coolant.

6061T6 is really nice to work with, not gummy. You can see pictures of my setup milling 6061T6 in my post about building Lew's magnetic clock.

Thanks for all the replies and suggestions. The cast aluminum is going to the scrap bin.

[winchman]

I've seen some cast aluminum auto parts that machine very nicely without coolant at the same speed/feed I use with 6061-T6. It just made a buzzing sound as the tiny chips flew off, and the finish was pretty good.

Cast aluminum tooling plate is one of my favorite materials.

[baldysm]

At home, I use lard when I'm cutting aluminum. Works fantastic. It's like a gel and stays a gel until it warms up a bit and becomes a thick liquid. WD40 is supposed to work pretty well, but I've never used it.

Either would really help solve the loading the cutter problem your having.