
I only cut annealed tool steel and these cutters absolutely cut through it unlike any other end mill in my box. Not only that, I get more durability out of it than my carbide. I've been cutting tool steel with one of these 2 days in a row and it still works perfectly. I'm stocking up because that's all I'm using now. For the price they are unbeatable. m42's strength, shock resistance and resistance to vibration damage is much better than carbide, carbide has almost no place in my drawer. A bad vibration and smoked carbide. They can take anything thrown at them.