The statements that milling machines cut at much slower speeds than wood is not quite true. Modern machining centers use speeds of up to 40,000 RPM to mill the metal and with only a fine mist of coolant sprayed on the cutter. The speeds are accompanied by equally high feed rates. The main thing to remember is that the chips coming off the bits are very fine, almost fluffy and they take the heat away from the bit and the part being cut, unlike the mills in the past that took a slower heavy cut that was flooded with coolant for lubrication and of course cooling.
My knowledge is first hand as we machine aircraft wing ribs from aluminium plates 6" x 24" x 72" to 84" in about 4 hours each.
If you decide to route aluminium take light cuts with sharp bits. I would also add to the advice of not climb cutting, don't make any cuts that won't clear the chips, like dovetail or 'T' slots.
The process is nasty and you will want to wear long sleaved shirts buttoned to the top, gloves, eye protection plus a face shield, and ear protectors. Unlike wood chips those alloy ones are sharp and hot, and are not in the least bit comfortable when they settle and collect in your belly button.
On several occasions I've used my trim router with a 1/8th round over bit, dry, to break the edges on some electric motor mounts that I got the foreman (ssshhh!!!) to make for me, without any problems.
There is some differences in aluminium alloys that affect the way they cut. The alloys commonly used in aviation (2000 & 7000 series) route cleaner than the softer commercial (1000 & 6000 series) in my experience. The commercial alloy 6061 being most commonly used by manufacturers to make aftermarket woodworking accessories has a tendency to 'stick' to router bits because of the relative softness that the harder alloys don't. If you're getting metal from a scrap dealer and can get the harder aircraft alloy don't pass it up unless they are trying to charge a lot more for it.
