Whats the difference between Phillips, Pozidrive and Robertson (square) screws?
Philips drive screws are the screws that have cross-slots that look like an X, stamped into the head. Patented in the 1930’s, these were a vast improvement over the antique “slotted” screw, which tended to cam-out easily and were difficult to drive with power drivers. Robertson (square) drive screws were patented in Canada in 1908 and address problems that the Phillips driver doesn’t quite solve. They allow the screw to be placed on the driver prior to the screw being placed in position. What this meant was that for the first time you could start a screw overhead or in a tight spot without an extra hand holding the screw onto the driver. Pozidrive screws answer the Phillips shortcomings. The differences are subtle. At first glance it appears to be a Phillips, but on closer examination you’ll notice a second set of cross-blades at the root of the large cross-blades. These added blades are for identification and match the additional makings on the head of Pozi-drive screws, known as “tic
