The square shank bit wears out over time so when you drive the bit in, it catches and stays in the head of the screw instead of the screw head to stay bit holder. Or he jumps instead of turning the screw and tears the screw off. I have to constantly pry them off the screw with the Knipex, provided they stay in the screw long enough to tighten. The key appears to be a black coating on these screws. I've had brand new bits that lost their coating and therefore shrunk after only 4-5 screws. I have used a variety of screws including Spax and Kreg brands which are very good and these Makita bits will skip, work loose and get stuck on the screws. I switched to a pair of *uncoated* cheap general purpose attachments and they worked just fine. All screws were screwed into soft pine, white wood and other frame materials. Nothing permanent like oak. These bits are useless.