My old co-worker at the ski shop would spend hours and hours hand-tuning his skis. One of our colleagues was really into it, and they'd use all kinds of files and bevels to sharpen and detune their edges for hours on end, then they'd wax their skis with strange powdered wax that cost absurd amounts of money. The first time he went skiing after all that tuning, he caught an edge and flipped into the woods cracking a couple bones. I thought it was a coincidence that he caught an edge after tuning his skis this special way, but he went back to using the machines to tune them. And that next time he tuned them himself, he stripped the entire base and edges off one of his skis by passing it through a stone grinder with improper settings. I suppose he could look on the bright side. Even if he didn't have a bunch of cracked ribs, he still wouldn't be able to go skiing anymore.