Aluminum alloys. If I look at HSMAdvisor, and I input a 0.75" 3 flute bit, and a 0.25" DOC, slotting 6061-T6, it gives me a feed of 119 IPM, a power of 6.73HP and a cutting force of 204 lbs.
I'm not sure if my machine will be able to handle this, but if it can, I think that is around the maximum I would want to push it.
I'm pretty new to this program, but it does give a cutting force, which is nice. My performance estimate doesn't include bearing friction or probably a few other things that don't work in my favor, and the motor torque vs speed graph, who knows how accurate that is, so I figure that if I have 300lbs of cutting force available between 0 and 100 IPM and 200lbs available between 100 and 200 IPM that I should be fine. I think an acceleration of 0.3G is what I'm aiming for. Is there an error in my logic?
As always, a big thank you to everyone who has contributed to this thread!