Aluminium powder CAN be made successfully by employing a coffee grinder, this has been tested/proven by myself!
I mean, its not exactly 400mesh when your finished, but its fine enough for use in Al/FeO thermite mixtures, and it makes pretty fuckin good flash powder, Al/KmNO4
Grinding Al foil by itself will obviously fall short of powder, and yield pellets suitable for an al/hg amalgum.
The trick is to grind the Al foil (already trimmed down to 1x1 inch squares) together with a quantity of SALT!
Now i generally add a handful of salt per load of Al.
I own about 6 breville coffee grinders, all single purpose, so a load consists of a full grinder, more or less!
Now, it will take around 15min to get the powder you desire.
DONT take the lid off halfway to check it out, you dont want to inhale Al dust, NOR do you want your face to be charred IF the Al particles ingite when exposed to air.
So, once you think your Al is ready, slowly and carefully take the lid off, and slowly pour the mixture into a 250/500ml beaker full of cheap denatured alcohol.
The alcohol is there to dissolve all the salt, so make sure you have enough! Now the thing is, when i first tried this, I added the Al powder/salt mixture to dH2O without any problems at all...maybe i was lucky, who knows!
Yeah, so you guys get the drift, decant the alcohol and then spread the Al powder out to dry on paper towel or something.
Now, It has been recommended that a small amount of parrafin wax be added to the Al/salt mixture to reduce friction and to make the process safer. Refine any way you like!
Either way, its a good source of cheap Al powder.