I just ran a keyseat cutter to make a t slot on a block of steel to run my mill as a cnc lathe, it was to hold the t nut of my tool post, the first pass had the cutter engaged on both the left and right about .300 on each side or more, cant remember, I used air and a little oil to clear chips. about 3 inches of cut, its still feels sharp as new, but it was not a fun cut to make, it was like parting, i had to maintain perfect feed or tool pressure or it would get all squealy on me. I ran about 300 rpm, maybe .75 inch/min