[rob love]

Aside from the painting problem, the finish resists corrosion and seizing. While those plain finish bolts may look OK, you won't be so happy in a couple years when you have to cut or break them all off.

Grade 8.8 metric is the equivalent of our SAE grade 5 bolts. As to putting grade 8 (or 10.9 metric) on everything, that is fine 95% of the time, but there are applications where you prefer the bolts to bend slightly than to shear, so you should use the correct grade of bolt. Frame applications come to mind....in many spots the lower grade is the correct bolt to use.

The DIN 933 merely is the standard (vs DIN 931) of whether the bolt is only threaded on the lower portion or if it is threaded all the way up to the head. DIN 931 is partially threaded, DIN 933 is fully threaded. Mind you, on short bolts, both specs result in the same product.

If you really want to get confused, I have seen bolts with both the metric rating and the SAE markings (lines on the head). When you see those, you may need to get out the pitch gauge and the calipers to figure out what they are.

I used to manage some pretty good nut and bolt selections when I ran various tool cribs over the years. The non-mechanic users often displayed problems understanding the metric/vs standard, the grading systems, and even the fine/course factor. The best bet in the end was to put a cage around the whole works and only the mechanics got a key. Not only did it reduce the number of metric bolts stuck into standard holes, but it also sure cut down the wastage and pilfering, much to the dismay of many of the combat arms fellows.