We cut tungsten quite a bit. I run it using standard Tialn coated carbide endmills. Our parts are somewhat large for tungsten most have been in 6" dia range x 12" long. I run it at 150sfm .002 base chip load on 1" tool. I usually step down at 40% of tool dia and will do full slotting. I must also mention that all of our machines are cat 50 machines but so long as you have a decent setup going on you should be ok on a 40. It won't chip the material at these rates and I have never had a problem with chipping. The chips break up in your hand somewhat like cast chips but alot harder. I use garr 1280h drills at 115 sfm at conventional chip loads for approiate size of drill. 300 sfm will eat tools for breakfast all day long on tungsten. 150 you will get decent life out of your tools.