this hot rolled steel cut fine. next up this weekend I hope to have time to cut out some motor mount brackets from 4140 chrome moly steel.
I just wanted to post up my results so people see what these machines are capable of making some real strong parts for things.

I used a lake shore carbide fire plug 3/16 variable flute stub carbide roughing end mill. the short length makes it ridged, the variable flutes keep vibrations and harmonic chatter down. but most importantly I have an air/oil sprayer from trico, you have to have some type of cooling for the bit and work piece and the oil(not wd40) will reduce friction keeping the heat down further. the air also works as chip evacuation and that is more important than anything. you can brake a carbide bit plastic or wood even without proper chip evacuation. you can get super cheap coolant sprayers and little compressors on amazon or ebay, even craigslist if you are in the states.
http://www.lakeshorecarbide.com/fireplu ... dmill.aspx
30 ipm, 10 plunge, .015 depth of cut, .2 step over. this is what I have run all my first cuts with a new materials or new bits at. with the looks of things can cut much deeper and faster on my future steel cuts.
make a mess and have fun