Manual says to hold for .5-1.0 second - I`ve tried .5, 1.0, 2.0, 3.0, 4.0 and 5 seconds with no success? I ended up welding a piece of metal on and using my big slide hammer and worked fine. I`m not even sure the studs would be strong enough to pull the thicker metal even if they were holding so I`ll just keep going with the welding and slide hammer method.