i was up to the 18-20 hrs per head, but i did it over time. a few hours each day, its nothing you want to sit down and do for 8 hours straight.

and for sure your not gonna do any huge damage from a run away bit or nothing. worst thing you could do is nail the valve seat where the valves seat up. thats a sketchy area in the bowl. after you do a few bowls, your like ok, here we go again lol