looking at your pictures, i had a hell of a time doing something very similar in a-36 steel. i was trying to use a 4 flute 1/2" carbide endmill full width with a finish depth of about an inch. i could not get the chips out of the way and i was killing my endmills. on my project, only the inside diameter was critical so i made the cut .75 wide instead. i'd make a full width pass around and then the next pass was only 1/2 the cutter diameter. i'd go down in z and do the same thing until i got to my final depth. this kept the slot wide enough compared to the depth that chip evacuation was much easier and recut became no existent.
i think 1" deep, 5/16" wide is going to be very tough to get the chips out of the way without some serious coolant pressure. i think chip evacuation is more of your problem than the material although i don't have much experience with stainless.
edit: if you don't need to save the plug that comes out of this, what about doing a circular pocket? this would allow plenty of room for coolant. sure it would take longer but it would probably be cheaper than replacing endmills.  |