Maybe swage is not the right word. I spent several weeks attempting a flare fitting connection and couldn’t get it right. I had another HVAC tech out to attempt a flare fitting and he couldn’t do it. The second tech I called did…whatever the other kind is. Expand one side of the copper tube, insert the other side, use heat and flux and solder to join them. By this point I didn’t want to invest more time into the project (again, I did every other part of the install, including multiple other flare connections). I vacuum pumped the line sets and am pleased to report they work great now.