I used my 51430 drill bit to cut 4 door and 4 window openings on 2 teardrop trailers through .030" anodized aluminum. Used ones were rejected halfway to the holes in my photos. I like the double bearings and the cut. In my opinion, Amana has always made the best cookie cutters. It might be a bit more expensive, but it's a lot cheaper than replacing a few low-quality bits to do the same job.