I did this today as well. I used Bobby_M's jig, and I didn't even use a whole disk per keg. I was surprised at how well the Norton disks worked. I spent a $1.60 or so on the disk and cut the hole in about 3.5 minutes! I'm usually not a DIY'er but with the help of this forum and my desire to become a better brewer, I'm quickly jumping head first into the DIY projects!