Screw Head Types
PoziDriv® (SupaDriv®) Head
Although PoziDriv® and SupaDriv® were the original names for this type of configuration they are more commonly known as PZD/SDV as this is how the European Standard now refers to them.
This drive system is a further development of the Phillips head and in fact was developed and patented by Phillips.
A PZD/SDV screw can be easily distinguished by a line stamped in the screw head at 45 degrees to the slots for the driver.
Whilst it is similar in appearance to the Phillips cross-head, it is in fact quite different. The biggest advantage it offers is that it does not tend to cam out, allowing more torque to be applied.
How does this work?
If you look at the tip of a Phillips screwdriver (left) you can see that the blades taper towards a point. In use, it is this tapering that tends to push the screwdriver out of the screw (cam out).
The PZD screwdriver (right) has parallel blades. This removes the tendency for the screwdriver to be pushed out of the screw head. The PZD tip also has 4 more points of contact with the screw to deliver more torque.
All this means that more torque can be applied to tighten a screw than can be achieved by a standard Phillips type screwdriver.
The Phillips screw company lists the following as the PZD advantages:
Extended drive tool life
Reduced cam-out at higher torques
Reduced worker fatigue through less effort
Improved manual and automated operations
Eliminates damaged screws
Increased cross-sectional strength - stronger screw heads
They're self centring
Screwdrivers for these screws are produced to DIN/ISO 8764.