Secondary Spot Welding

Hello! I have a question for you: made spot welding from an old electric welding, rewound it with a welding cable of 70 squares. The essence of the question: should the coils fit snugly to the core or CAN THE RINGS BE WIDE THAN THE CORE? I have randomly and much wider! How come! Are there any losses or trance works at 50%? But the turns are not wider than the primary ones, but not tight!