jsharris, on 17 April 2016 - 07:02 PM, said:
PH (Phillips) have a more acute angle, narrower blades and tend to wrack out. Pozidriv (PZ) came about as an attempt to improve on the weaknesses of the Philips head when used with power drivers. Neither have bits that last long unless an impact driver is used, IMHO.
If by wrack out you mean "cam out" then it's intentional. Philips screws are designed to be used in industrial processes and are usually fitted by machines. The requirement of the bit and screw head to separate easily when a required torque is met is essential to a dumb device like a mechanical screw driver not wrecking the screw, work or both.
In the context where we use them: plasterboard, decking and other large expanses where thousands of screws are driven Philips heads are used for the same reasons. Your life gets a lot easier when you buy a collated screw gun and fit your plasterboards with it. 2000 screws in an hour, each one perfectly sunk to the level of the board is a lo better than fumbling round with an impact driver and tub of screws, even if it does have a deph stop
Philips and pozidriv screws should always be used with their respective bits.. There's a massive difference between the two ("it's not just "a plus shaped driver is for screws with a plus on the head") and using one with the other is the fastest way to a wrecked bit, or wrecked screw. Most my pz2 bits have failed through snapping the vanes off (with an impact driver- usually because it was set to the wrong direction and it's a lot harder to tell than with a normal cordless, or that with being used for screw in as well as out, the different directions introduce stresses that break them) or when it's just got too worn and become prone to skipping. The ph2 bits I have still look near new, and I'm 9000 screws in to one of them (the other just sinks the odd plasterboard screw that the gun leaves proud). That's not to say it's better; their duty is a lot lighter than what I ask the pz2 and 3 to do.. But I dare say it's not real possible to equate the two or say one is worse than the other, they're just different