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