1/4 inch breakage in mild steel. Now I know you must be thinking that this guy is an idiot and doing something stupid. Fair enough... But it was mild steel and the tip broke a bit right away. The rest works fine. But on the other hand, I no longer used them in steel, only in aluminum. That's it. I read a review and someone says they broke a tool, I immediately think "well I know what the tool was" and dismiss the reviewer as an idiot. Every story has 2 sides and luckily these parts have 2 sides. So a quick turn and more holes were born. Since I still had to buy a center drill, 3 stars for you.