Most "normal range" PZ screws are PZ2. Big ones say from No.10 (No.12?) and up are PZ3. PZ1 from No.4 down?
The fit of the bit into a PZ head is fairly positive provided the driver and head are not baddly worn. The point of the driver should fit flush with the head not disappear into it (PZ1 or 2 into PZ3) or sit proud (PZ3 into PZ2 or 2 into 1).
That is not quite as clear as...
I've yet to see a PZ bit that didn't have the corner sections in. I was under the impression that they were part of the design rather and a manufacturing restriction.
I'm talking bits/driver not heads... Though I guess you can peer onto the end of the bit/driver to see the fillet in the corner of the driver but that isn't necessary.
Compare a side view. You'll see the corner fillets. If they aren't there, it's a philips.
They are caused by having to have the grinding wheel at 90 degrees to the shaft. Its damn difficult to not have them using grinding wheels to shape the blade. I believe I saw some that appeared to be forged to shape and they didn't have the leftovers.
Interesting article;
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