I did that relief on a precision tool grinder called an "Ewag"
It is an exspensive machine (swiss) that is used to make carbide cutters, reamers, custom cutting tools. I bought a wheeel for it to cut high speed tools. I use that wheel to grind the cranks. The machine is at work, Wish I could afford one for the garage lol (about $150k)
I first tried cutting the Norvel cranks with carbide, didnt even touch it