I've got a bike with an old, cup and cone bottom bracket that is having a little problem keeping the left side crank attached. I would like to really lean on the tightening nut, but I'm not sure how much torque I can apply and don't want to risk breaking the BB. I searched BF and Sheldon Brown, but could not find the answer. Does anyone know how much torque I can apply to the retaining nut? If not a number, just a general how hard can I 'lean' on this thing?