Patent ID: 6988432

Claim:
A screw and driver system, the system comprising a range of screws including a set of larger screws and a set of smaller screws and a driver operatively compatible with each one of the screws of the range of screws for rotatably driving the screws, each one of the screws of the range of screws comprising a head having a driving recess defined on a surface of the head for engagement by the driver and a longitudinal axis, wherein each one of the larger screws of the range of screws includes a plurality of first superimposed recess tiers of decreasing size with increasing depth from the surface of the head, each of the first superimposed recess tiers having substantially parallel driving surfaces substantially parallel to the longitudinal axis, and wherein the driver and the first superimposed recess tiers are shaped so that, when the driver is engaged with the first superimposed recess tiers, torque applied to the driver is transmitted to the screw through the driving surfaces; wherein, each of the screws of the set of smaller screws includes at least one second recess tier which includes a rib extending substantially parallel to the longitudinal axis of the screw and encroaching into a space defined by the second recess tier and which space is occupied by the driver when it is engaged with the second recess tier, whereby engagement of the driver with the second recess tier causes deformation of the rib and hence creation of an interference fit of the driver in the second recess tier.