I've milled no end of aluminum and brass on my Sherline CNC mill but pretty much avoided steel until now. Especially stainless steel. The Sherline is pretty much a flyweight among mills and I always thought that the tougher materials should be avoided.
I needed to make two cam lobes for Jan Ridders designed Atkinson I.C. engine. As most of you know, not all steel, aluminum, or brass etc is created equal. There are many alloys available. I did some googling and found that 416 stainless has the best machinability rating so that's what I used. I found very little reference material on machining steel on the Sherline mill.
In the end, I was most pleased with this experiment. Next time, I'll increase the depth of cut a bit but on such a small job, it didn't kill too much time going so light.
Here's a video of the milling. I started with a piece that I turned on my lathe which kept the mill time to a minimum.