If you use a rated chain and then weld it the metal in the chain would not meet the same SWL as it did before. SWL means safe working load. Hammer locks should be used to attach the chain to the drawbar.
Sent by iPhone while on the crapper.
You actually can't use hammerlocks to attach the chain to the draw bar. The rules state it must be welded, but as you said, most alloy grade lifting chains are not meant to be welded or the rating will be significantly reduced. Interesting as to how you are supposed to weld a steel chain to a alloy drawbar if that's what your trailers made of.
I think supercheap only sells shackles as small as 3.2t but they will be too big to fit through your chain. You need the smaller 1.5t or possibly 2t and I got mine from the local Bullivants specialist. I think I have now seen them at bunnings too if you have one close by.
Cheers
Wes
