Screwdrivers don't have a round head, because a round head has no torque at all. The word is to guarantee torque, and the cross allows the force to be distributed more evenly. According to the power source, there are manual screwdrivers and electric screwdrivers; according to the batch head or the cutter head, there are a flat head and a cross (phillips).
The head of a high-quality screwdriver is made of spring steel with a relatively high hardness. A good screwdriver should be hard but not brittle, and tough and tough. When the opening of the screw head becomes bald and slippery, you can hit the screwdriver with a hammer to make the groove of the screw deeper, so that the screw can be unscrewed easily. Do not bend. In general, it is hoped that the hardness of the screwdriver head is greater than HRC60, and it is not easy to rust.
