I think originally the screws would cause the driver to cam out and stop driving if a certain amount of force is applied but the screws are so soft and cheap that the harder driver damages the screw head when it cams out.
This and the centered shape that Philips and Robertson have were key. The lack of a sharp driver bit being able to slip out of the fastener prevented a lot of injuries.
I think originally the screws would cause the driver to cam out and stop driving if a certain amount of force is applied but the screws are so soft and cheap that the harder driver damages the screw head when it cams out.
This and the centered shape that Philips and Robertson have were key. The lack of a sharp driver bit being able to slip out of the fastener prevented a lot of injuries.
However, Philips, at least, needs to go away.