Made a random orbital sander attachment with 8mm movement, to be used with drill, angle- or bench grinder.
Note, that centrifugal force that makes backing to spin, also increases its spinning speed higher than the actual speed of the used motor. This happens when its unloaded. Personally i think that using 11-13.000 rpm angle grinder is possible too much.
I used backings made to be used with 13.ooo rpm speed, and 2000 rpm with my angle grinder, ( it has a variable speed.)
My bench grinder runs 2200 rpm. I originally planned this build for to be used with bench grinder.
Works nicely, and gives smoother result than my bosch sander which has only 2.5mm movement.
When mounted to bench grinder, i can use whole area of the paper for sanding, use my both hands for holding the object,
and it doesn't leave disturbing scratches.
Finished surface is much better than with the traditional disc sander.
Somewhat easy to make, cheap, small. Balancing takes some time. I used two days filing it to the right size and weight, but i think it was worth it. With better pre-designing i could have saved some time, but i just like to design while i make.