Non 'powered' DA machines (unlike the flex mentioned above) should really rotate about 1-2 times per second. A little mark on the backplate or on the top of the pad should help you to gauge how fast it's actually turning. You can only really regulate the speed at which it rotates by adjusting the pressure, but I know exactly what you mean - sometimes to get it to spin you need to almost lift it off the surface but then there's not sufficient pressure to do any meaningful work. Apply the required force and it tends to stop turning - it's a tricky one, for sure
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