I found this swaging punch on Klein’s website, and it got me wondering just what swaging was. It turns out that swaging is changing the diameter of tubing by forcing it into a die — so swaging is somewhat like flaring. After you swage the tubing, you usually mate it with a fitting, then crimp or solder it. Although swaging can be a hot or cold process, you’ll probably want to use this swaging punch cold.
To make their swaging punch, Klein precisely machines high-alloy steel then heat-treats it to make it strong and durable. The stepped design of their swaging punch allows it to swage six sizes of tubing: 3/16″, 1/4″, 5/16″, 3/8″, 1/2″, and 5/8″ OD. If the punch gets stuck after you drive it into the tubing, you can turn the hex head with a wrench to help extract it.
If swaging is in your future, this tool will set you back about $20.