I fought for 2 hours (it felt like 8 hours) drilling the first bolt hole with a bit that I thought was in pretty good shape. When I finally broke that one & went & bought a new one ... Oh me Oh my ... what a difference. The second hole only took minutes.
Yer right though, hang on. With a good bit that large, when the bit punches through, it'll grab. If you can find one, a drill with a side handle helps a lot.
Man - I had to be careful how I wrote that first sentence lest LBUD quoted me on it and turned it into sumpn dirty.