I have a static strap that is a 36" piece of light chain with an alligator clip on one end and a 4X1" strip of copper on the other. I stick the copper in my pocket or in my waistband, and the clip on the grinder base plate. there is a 1 megohm resistor between the clip and the chain for safety against AC shock. If I walk away from the grinder, the clip simply pops off the base plate and the chain hangs down by my leg. Only in the worst of winter do I use it now, as the laundry static spray ends the problem most all the other times.
What causes the problem is that the belt acts as a static generator. A glass platen makes it more efficient, but even a steel flat platen will build up static potential. As it builds up a potential, the nearest object....your blade...which is connected to you...is the discharge path. The mini-bolts of lightning can really make you jump, and that can cause grinding problems. It requires dry air for the potential to build. The cooler the air the worse the static, too. In the damper summer air, the static dissipates through the moisture to ground as it builds, and there is no shocking.
When I used to work in the Blue Room of the control towers ( doing electronics) we had all sorts of straps in out shoes and such, because the rooms were kept super cold and the lighting was "black light" You could hold a fluorescent light tube in your hand, walk across the carpeted floor, and touch the door knob with the end of the tube...and it would flash like a camera flash as the static discharged. You quickly learned how to ground yourself on every metal object before touching another person.
