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I did wood working for years in China, building backyard decks, pergolas, etc.
I wouldn’t say I’m a carpenter, it’s more of a hobby, but I consider myself a seasoned worker.
After I moved to Canada, I bought some Ryobi tools and built a flower rack.
While building it, I found the drill bit kept camming out of the screw head, which was very annoying.

I checked the bit and saw a mark “PZ 1” on it, which had to mean something.
After searching online, I figured it out!
There are two types of cross-shaped bits: PH and PZ.

  • PH means Phillips Head, which has 4 flanks and is commonly used.
  • PZ means Pozidriv Head, which is similar to Philips but has 4 additional small flanks, making it better suited for high-torque situations.

The number after PZ or PH indicates the head size.

To ensure a proper fit, screws also have the same mark on their heads.
If the bit and the screw don’t match, they will cam out.

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