Step 3The result.
iImage Information

Shown is the subtly squared tip, showing a distinct "X" in the cross section. This is what grabs the screw, and what you want to end up with. If in doubt, try it with a screwdriver you don't care too much about, periodically checking the fit with a few different types of screw heads as you grind it, and stop when you notice a distinct improvement in fit. I would be interested in feedback from other people as to whether they find this situation to apply as generally as I do, and from anyone who can explain why most screwdrivers sold suffer from this "pointy-ness" problem (is it just a matter of quality control? are they designed for ideal screws that no one manufactures?) and I hope this helps prevent a few mangled screw heads. If someone knows of a reason why this is a bad idea, please comment about that, too. Happy screwing.
But more likely it is just sloppy fabrication techniques.
I have also ground down the outside edges of the wings, very slightly, just enough to give a square edge to them, they grip better that way. But the best technique is to buy the best quality magnetic tips that you can find.