To continue furiously flogging this dead horse, the is an illustration of the problem:
![](https://stunthanger.com/smf/engine-set-up-tips/os-46-la-screws/?action=dlattach;attach=320752;image)
Note that not only is the proper driver much more blunt, it is also a different angle and much thicker individual blades. The point on the Phillips bottoms out in the screw and does not allow the individual blades to reach to the ends of the slots. That, and the fact that the blades are far too narrow to make contact all the way across, makes the pressure where it does touch much much higher for a given amount of torque, basically is it touching at best on just the edge, and then on a small part of the edge.
The proper driver makes contact from the bottom all the way to the edge, and completely fills the slots, greatly lowering the pressure on the interface.
The high local pressure is what causes the metal to yield. I checked with my hardness files, and the OS screws in the 46LA are about as hard as the Allen cap screws that come in the 40VF. The problem is not the metal, is it creating high local pressures that damages the slots.
OF course, with this knowledge, you could, if you were pretty careful, grind a Phillips driver to the same shape as the JIS. Not only do you take off the point, you have to grind the blades at a slightly different angle, and far enough up the shaft to catch the blade as it widens out. Unfortunately, that also makes it catch the slot up on the curved part of the blade cutouts, so you still have a problem, just not as big a problem as before.
But of course, once you note that you can get the right screwdriver fo $5 in a few days, that all begins to look like a lot of work that you could avoid, and do something useful instead.
Brett