i was thinking of a 20mm diameter piece of thread with a high thread count.. and running it directly from this: http://www.makitauk.com/products/cor...ct-wrench.html

i think the "impact" side of things would really help with penetrating stuff too as it's not so much a continuous pressure but constant hits each time. 2200per minute to be exact.

the problem I'm seeing though is for as much force this will produce it will recive back down the shaft to the gearbox which it isn't designed for..
so would maybe have to put a sprocket on the base of the thread and use the drill (also with sprocket attacked) to turn it. So the force isn't put back into the drill motor/gearbox then.

Its something I would like to test out, but really don't know what upward kg force it would produce. I think it would be a fair bit as these impact wrenches are beasts.