The Corona Mill is a cheap alternative to the more expensive roller mills used to crush grains for brewing. Roller mills start at $100 and quickly go up in price. A Corona Mill can be had for as little a $20. With three modifications---two minor, one a little more intense---it can be as effective or even more effective at crushing grains for home brewing. The lower cost will let you save money on other things like good brewing kettles, jet burners, and pumps.
Step 1: The Handle (Manual to Motorized)
This tip has been out there on the internet for a long time. The handle is held on by a thumb bolt. You can replace this thumb bolt with a 5/16" bolt and then use a 1/2" socket on a drill (or some other motor) to crank out your cracked grains.
Step 2: Another Minor Fix
This is another tip that's been out there a long time. See the exposed gap where the bolt is. Fill that with washers. Most tips around the internet say two. I say four because of the next mod.