The answer to this is always "very tight". The manufacturers figures are really quite high if you have a torque wrench or similar, and the average person leaves things too loose. You may have noticed that all the CU screws these days are not brass as of yore, but zinc plated steel, as are the neutral and earth bars. This is to make the torques sufficiently high that thermal expansion never removes all the preload from the screw. BTW 60nM and an M10 grade 8 HT bolt is quite small, it will stand at least 200 nM (that is a 20kg push on a 1 metre long spanner, so easily done). I have a 650 nM air impact wrench which will sometimes just break M10 (rusty) bolts, which is sometimes a useful dismantling technique if they have nuts as through fixings, or on old exhausts it saves getting the oxy gas out.

The answer to this is always "very tight". The manufacturers figures are really quite high if you have a torque wrench or similar, and the average person leaves things too loose. You may have noticed that all the CU screws these days are not brass as of yore, but zinc plated steel, as are the neutral and earth bars. This is to make the torques sufficiently high that thermal expansion never removes all the preload from the screw. BTW 60nM and an M10 grade 8 HT bolt is quite small, it will stand at least 200 nM (that is a 20kg push on a 1 metre long spanner, so easily done). I have a 650 nM air impact wrench which will sometimes just break M10 (rusty) bolts, which is sometimes a useful dismantling technique if they have nuts as through fixings, or on old exhausts it saves getting the oxy gas out.