Indiefan
If you are having still having trouble it may be because there are many factors that go into a good part setup. First you said you are using a four flute end mill, this is not the preferred tool for your material, and a two or three flute would work much better in that it would not tend to clog up as quickly.
Coolant is also important when cutting aluminum, along with what type of cutting you are doing such climb milling, conventional milling ,pocketing or channel cutting .The type of machine you use will also affect your results. Are you using a cnc mill? , a standard mill?, or a bench top mill ,each of these machine have different spindle speeds and rigidity .
I am sorry for not answering you question with a number (ie cut .125 deep) but as you can see there is no simple answer. I would be happy to help you with making what ever you are making .I can sent you a cutter and a nice little slide card that make calculating speeds and feeds much easier.
Let me know how it woks out and if you need some help. Your friend on team 107.
Jim Schaddelee
Team 107 mentor
