I may have missed it, but one thing I have not seen in this thread is the point that there is usually a fairly wide range of torque for a bolt, say 6-8 nm. What is really important, and what you can't do by hand is to tighten all clamp bolts to exactly the same torque. This is important so that all the bolts are under the same load. When I tighten clamp bolts on my steer tube I do each one 3 times, and each time the bolt tightens a bit more, you can't possibly tighten bolts by hand and get them to exactly the same torque, which you can do with a torque wrench.