Without reviewing the proposed weld tooling you will be using, it is
hard to give you an exact answer. The general rule of thumb is that
spot weld pitch, centerline to centerline, is normally 3 to 7 times the
nugget size.
Sorry about the late response,, Scott has given a good answer ; not knowing your equipment . I've been away from spot welding for quite some time but talked to one of our engineers that has stayed with it; he says that the big 3 automakers with their guns don,t usually get closer than an inch and would like to stay an inch and a half away. Your most accurate info would come from the manufacturer of the equipment.