I had to drill them myself. Actually it wasn't that bad with a drill press. It's true the metal is hard but the bits do go through if you feed the bit through with patience. I think I broke one bit but I'm pretty impatient. The hardest part is actually the curve of the bolt head. You need to center tap the bolt head good and hold the bolt steady in a drill press vise. Then slowly feed the bit. Too fast and either the drill slips off the curve of the bolt or it snaps from too much down force. Once I got the hang of it, it was really easy.

Without a drill press and vise, it might be pretty tough.