The tack welder will only work if you are tacking at a contact
between two pieces which is their only contact with each other.
The nature of this contact, how large or small it is and its
firmness, will determine how much current you need and whether
you will get a successful tack or a mess. Once you have joined
two wires in a basket setting they can’t be tacked to each other
again. I believe that silver will tack. Tom Kruskal