Man, I never dreamed it would be so bad...a thin layer of stainless steel. I bought a new faucet a few days ago and it had a little mobile sprayer. My sink was not outfitted with one so it required an inch-in-diameter hole to be cut through to be able to install it. I'd never had a need to do this before in my life and had never given it a thought. Guys at home improvement places and hardware stores were telling me all kinds of ways to do this right. None of them turned out to be right, IMO. I had envisioned what turned out to exactly exist; a "hole cutter," which fits on the end of a drill. I thought it would be a snap. It wasn't. The first one cut a little, then the teeth apparently failed and I was just rubbing metal against metal and making lots of noise and heat. I bought yet another one (told by old guy working at store that it wouldn't fail, would do the job well with a little patience). It failed just a fast as the first one--20 more bucks down the drain as I had to buy adapter too for that one.
What I ended up doing was what I had in mind to begin with: Drill a succession of holes in a circle with regular bits, then pretty much punch out the hole. The hole cutters actually did help since the circular crease they provided from use allowed the bits to bite and stay in place when making the circle. What makes stainless steel so hard?