I Don't Need No Stinkin' Posidrive
- Gerry Masterman
 As of:  16 April  2006 

"I don't need no stinkin' Posidrive!"

        Yep, I've heard it before, many times, and generally just before Bubba stripped out the hole in the top of a Posidriv screw with a Phillips screwdriver. 

       Never heard of a Posidriv?   Ever noticed those funny looking heads on those Phillips head screws that are all over you Little British  car?  Well, better go look again.

 

If you do, this what you will see: 
Not this:

        What's the difference?  OK let's look and see. 

The picture on the left is a Posidriv and the one on the right is Phillips.  Notice on the Posidriv, the square center and the small cross between the big cross legs.  The small cross is embossed on the top of the Posidriv screw head.  The square recess is part of the opening that your screwdriver fits into.  Now look closely at the Phillips head on the right.  See the curved area between the cross?  Now think about what will happen if you try to use a Phillips screwdriver in a Posidriv.  What happens is the curved part of the Phillips bottoms out on the Posidriv screw before the tip is allowed to go all the way in.  Because the fit is extremely sloppy, the Phillips driver will try to twist out of the opening, and in the process, destroy the opening in the screw head. 

        At that point, the screw head is buggered up to the point that even the Posidriv screwdriver will not fit the screw head.  Time to break out the vise grips and hope for the best.  Been there and done that, haven't you?  Thought it was just a bad screw, huh?  Well, I'm here to tell you that if you had used the proper screwdriver, that screw would have come out just fine. 

        Why did our friends across the pond use Posidriv?  I haven't a clue.  But I know what to do about it - use the proper Posidriv screwdriver.  How do I tell Posidriv screwdriver?  Well, if you look real close in the area between the cross, you will see another set of ridges.  These ridges fit into the square recess I mentioned earlier.  

        So, to sum up, before you put a screwdriver on that screw, take a close look at the head.  If you see the telltale second cross and the square center hole, it's a Posidriv, use that Posidriv screwdriver, not that Phillips!

posssi.jpg (31346 bytes)