Basic questions for milling 6061-T6 aluminum

Let me apologize in advance if this is a stupid question or already covered 100 times. I've done some work on a ShopBot, but will be doing my first project on a Tormach Mill shortly. I need to machine a part out of 6061-T6 that will be roughly speaking a 1" thick, 3" diameter disk.

I assume I'll clamp a 4" x 4" chunk of aluminum in the vice, and cut out my part, leaving tabs to hold it in the larger chunk.

I don't know where to start to figure out the spindle or feed speed (or cut depth per pass). I've got to believe this is one of the most common materials to machine. I'd appreciate it if someone could give me a set of starting numbers or point me in the right direction.

Thanks.