All you need to do is place an expander ring onto the PEX pipe you want to use that's properly sized for the fitting you're aiming for, and then stick the tip of the expander tool into the opening.

Uniweld’s UEK1 Hydraulic Expander Kit for swaging copper tubing will save you time and money by eliminating copper fittings and solder joints.

My inspector says I can use PEX pipe, and it seems too good to be true. I've never worked with PEX, but I have some experience sweating copper tubing.

Expanding a PEX pipe with a Milwaukee ProPEX expander tool sounds a little complicated if you're not familiar with it, but in actuality, it's a pretty straightforward process.