How many lines to a column?
It varies. Torah scrolls tend not to have fewer than 42 lines per column. Some Megillot will have eleven lines per column, so as to have the Sons of Haman occupy a column to themselves but still have only one on each line.
The Keset ha-Sofer:
It is the custom to have no fewer than 48 lines, representing the journeys of Israel, and some say no fewer than 42, because of what God did in the Sinai wilderness at Kadesh. Also, we don’t have more than 60 lines, representing the 60 myriads of Israel who received the Torah. This is because the beginnings of sanctity start at 48 or 42 (the wanderings in the wilderness) and continue to 60 (the giving of the Torah). If one makes it different it isn’t invalid.
Good thing too, that last bit – I saw a 70-liner this afternoon.
See? 70-line Torah Column of Doom at left; compare to 42-line Regular Column at right. I would need to stand on a chair to read from that big one.