Instructables

Step 13: Posidriv®

Picture of Posidriv®
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Pozidriv was jointly patented by the Phillips Screw Company and American Screw Company in the USA. Developed by GKN in the 1960s, the recess is licensed from Trifast PLC in the rest of the world. It is the de facto standard in Europe and most of the Far East, where Phillips is almost nonexistent. The proper Pozidriv screws have a flatter bottom to the socket, and steeper sides, so the driver doesn't cam out as easily. The name is thought to be an abbreviation of positive drive.

Pozidriv is similar in appearance to the classic Phillips crosshead, but in fact is substantially different. On close examination you will 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 Pozidriv screws, known as "tick" marks, single lines at 45 degrees to the cross recess. So, the marks are for identification purpose. Pozidriv also does not have the rounded corners that the Phillips screw drive has. The tip or the driver is blunt which also helps it to seat better into the recess in the screw, unlike the Phillips which comes to a sharper point.

Identified in ANSI standards as type IA. Pozidriv drivers will not turn Phillips screws; but Posidriv screws can be turned by Phillips screwdrivers, although they should not be used as they tend to ride out of the recess and round the corners of both the tool and screw recess.

Advantages and Disadvantages of Pozidriv

The largest advantage it offers is that, when used with the correct tooling in good condition, it does not cam out, allowing great torque to be applied. The chief disadvantage of Pozidriv screws is that they are visually quite similar to Phillips, thus many people are unaware of the difference or do not own the correct drivers for them, and use incorrect screwdrivers. This results in difficulty in unscrewing the screw and in damage to the slot, rendering any subsequent use of a correct screwdriver unsatisfactory.
 
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