I had some frigging rusted and tight high tension bolts to remove. M14 thread size, nominally 175 Nm, glued and rusted from 2006 underside of a Ford vehicle.....marinated in glorious finnish short summers and long winters with some salt on the roads....
Tried with a rachet....not wuite has space to coax all that it needs....breaker bar does not fit....possibility to put three extensions and then 3/4" T-bar comes out of car body and straight line to turn. Straight line is great. Three 1/2" extensions provides incredible amount of flex and it hard to keep it stable.
I had one chopped off 3/4" socket to start, some DN20 pipe (OD27 mm, about 2,6 mm wall) and 75 mm long 1/2" extension. Online calculator promised around 300 Nm of torque before failing....marginal, but that is what I had in hand.
Some lathe work to make tight fit fits to help welding. I did not have the right welding rods to weld tool steel and such...There is real danger of hardening the ends and make them brittle. Closest to proper rod was CromaRod 316L 3,2 mm thick that was just the right for the thick end with 100A, but thin end even 80A was getting way too fluid. I had to preheat the parts to about 200C to prevent nasty habits of the ready made tools to show up. Weld on the thin and critical end came out ugly, but looked solid.
To my surprice the extension worked like a charm. Other bolt came out with simple 3/4" T-bar. The other end was resisting really good: The bushing over the bolt had rusted up and rubber thingy was acting up like a powerful spring. It need nearly two rounds with 1,5 m long extension pipe over the 3/4" T-bar before breaking free....and came out a one piece!