I loved the sharpness and hardness of these powerful tips. I slightly centered the work before use and the center pins held the bits in place for the most part. Even when they slipped I also used cutting oil, that smeared things a bit, they stayed intact. I used a bit to remove the rear apron on a '68 VW Beetle. He has one life left to easily remove another. I was concerned about drilling spot welds, but after using them I now have no hesitation in removing the bottom. I love these beats and so