Tightening torque for metric bolts using T = K · d · F. The clamp load (preload) is taken from the bolt's property class and tensile stress area; the friction factor K depends on lubrication. Metric coarse threads.
T = K · d · F (d = nominal diameter, F = preload). Preload = % × proof strength × tensile stress area, with As = (π/4)(d − 0.9382·pitch)². These are nominal figures — real torque depends on the actual friction in your joint, so verify with a torque-tension test for anything critical.