I have no idea what that means. I do know he’s good at what he does. Got a friend of his hired at the same place, and was kind of shocked at how bad his friend is at math, whereas he can do most of it in his head. Welding isn’t all about the actual WELDING, as it is figuring out angles, etc. He took calculus in high school just to see if he could do it, not that he needed another math credit. Turns out it was a piece of cake for him. You would NOT think that about him if you saw him (typical hipster look... beard, long hair, etc) but he works his ASS off.
Golden arm is a slang term for a very good and precise welder.
This work was done by a golden arm:
https://i.pinimg.com/736x/9e/b8/36/9eb8368608f23824db57759e64c468fa.jpg
