It's funny that you mention that. Phillips don't feel quite right so I was trying Pozidriv.
Pozidriv is a European variant of the Phillips that is designed to prevent the driver flutes from riding out (or camming) of the slots in the head of the screw.
There appear to be 2 major differences between the two types.
Phillips #1 Screwdriver
The width of the flutes of the blade appear to have a distinct wedge shape to them. (middle lines)
The flutes are quite 'pointed' so they enter the hole in the screw head easily.
#1 Pozidriv Screwdriver
The width of the flutes of the blade appear to be parallel to each other (middle lines)
The flutes are not as pointed so the blades have more surface area that reaches down into the head of the screw. As a result you can apply more force.
My pictures are not great, but below is a much larger #3 Pozidriv that more easily shows the flute shape
#3 Pozidriv Screwdriver
I can really believe that the Japanese used a different profile that is 'close, but not the same'.
However, I started looking for JIS screwdrivers and found this article that says they are probably no longer made.
Apparently, the JIS standard is obsolete!
It sounds like Phillips and JIS screwdrivers have both changed somewhat to be better in both applications, but it is a trial and error search to find out which screwdrivers work better.
Who knew that finding a screwdriver could be such a pain in the butt!
The JIS bits work much better if you're working on imports. I bought a set of bits of Amazon for a few bucks. JIS isn't made to cam out when over torqued vs phillips (US standard) is meant to do by design.
I bought a set of JIS type Phillips screwdrivers and am impressed.
I don't really know if it's because they are brand new or that they are JIS style, but they work extremely well without camming out of the screw heads.
I removed a set of the cam cover screws off of a motor sitting for 20 years and I had to really torque on them. The JIS screwdrivers worked really well. #3 was the perfect size.
Thank you Gamble. I would have never thought about these drivers
They were expensive but they are very nice.
They have a solid steel shaft so one can actually hammer on them. As a result, they have great weight.
And the name: well..... Vessel Megadora. I'm pretty sure that's a monster that destroyed Tokyo.......
I wasn't sure about this, but the ribs aren't obvious or excessive.