It's not what you think.
Quite often, people will say that their Phillips screws strip out too easily. And where Phillips is kind of old school and less positive grip than square drive or Torx, there are still a lot of Phillips screws out there.
The most common problem that occurs when tightening (or loosening) Phillips screws is using the wrong size screwdriver or screw bit. Everyone seems to gravitate to the #2 Phillips bit, probably because it's the most commonly found bit. Call it the Three Bears mentality, "...and the middle one was JUST Right"
The reality however, is that a lot of the commonly used Phillips-headed screws, especially those above a size #8, are meant to use a #3 bit. And screws smaller than a size 6 usually require a #1 bit. If you don't have one of these other sizes, get one and try it out next time. I bet you'll be surprised how many fewer screws get stripped.
It's easy enough to talk about wood screws, drywall screws, deck screws and sheet metal screws. All you have to do is put the sharp end towards a hole and turn. Okay, maybe that's an over-simplification. But the fact remains that dealing with those kind of fasteners is much simpler than machine fasteners.
What makes a fastener a machine screw or bolt? They have a thread that requires another component to make them fasten... usually a hex nut or variation of that. The threads are very specific for each size and thread pitch. Similar to wood screws, sheet metal screws, etc., the size reference is comparable to machine screws. However, the thread pitch is very different. While wood screws and the like are designed to "bite" into a surface such as wood or metal, machine screw threads are designed to fit the corresponding nut.
When you see a hardware selection, such as we have at Town & Country Hardware, some of the bins will have sizes such as 8 x 1", or 10 x 3/4". Those are wood or sheet metal screws. Other bins will have sizes such as 8-32 x 1-1/4" or 10-24 x 2". These are machine screws. The first number refers to the size, or diameter, of the fastener and the second number is the thread pitch. Simply put, the second number refers to the number of threads per inch. So, an 8-32 x 1-1/4" machine screw is a size 8 in diameter, has 32 threads per inch and is 1-1/4" long.
I've never actually taken the time to count the threads to see if they're right, but I'll take their word.