The MGA With An Attitude
POZIDRIV SCREWS and Driver Bits -- TS-101

At 12:22 PM 10/6/05 -0400, Warren Arthur wrote:
".... the MGA door hinges need some sort of supersized Phillips head tools to remove them. .... I recall they were called "posi-???" and could be purchased at most Sears stores."

Those are POZIDRIV screws, and having the correct driver bit is VERY important.

Phillips screws and drivers have an intentional angle on the flanks so they will cam out of the slot before a power tool will twist off the screw head. This is (was) a creative production approach when the device was first invented, but it leaves a lot to be desired when it comes to field service of the screws.

With improvements in production tools to better control the torque of the tool the cam-out action is not necessary, and has very little purpose (except to aggravate people). The Pozidriv screws and drivers have straight sided flanks which are, not coincidentally, much more friendly for field servicing. With Pozidriv you can apply much more torque to the screw without having the driver bit jump out of the slot.

However, it is VERY important to use the correct Pozidriv bit with these screws. If you use a Phillips driver on a Pozidriv screw the bit will cam out of the slot just like it was designed to do, and when that happens it will damage the slots in the Pozidriv screws. End result is that the Phillips driver is even worse to use on a Pozidriv screw, and it will make a worse mess out of the screw head.

You can buy Pozidriv driver bits at Sears and other places in sizes up to #3. But the #4 Pozidriv bit seems to be a rare bird. I happened to find a good domestic source, and cheap too! Check here:

Lara Specialty Products & Tools
P.O. Box 2368, South Hamilton, MA 01982
800-620-5272 - --(link broken)--

#4 Pozidriv bit - $1.25 (+$4.95 shipping)
For all Pozidriv bits:
Click on "Workshop"
Click on "Specialty Bits"
Click on "Pozidriv"

See next page for more background on POZIDRIV screw and driver design.

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