(you need to pull the drill out periodically to let the dust out, and the distance of that pull increases with depth. But it is O(K1 * N^2 + K2 * N) where K1/K2 are pull-out and drilling-in (both seconds per mm), and for short holes most of the time will be drilling not removing dust.
(you need to pull the drill out periodically to let the dust out, and the distance of that pull increases with depth. But it is O(K1 * N^2 + K2 * N) where K1/K2 are pull-out and drilling-in (both seconds per mm), and for short holes most of the time will be drilling not removing dust.