For a proper fit and optimal solder flow, the copper pipe must be cut cleanly and squarely. Use a tubing cutter for this task. Place the cutter around the pipe at the desired cut location. Tighten the knob until the cutting wheel makes light contact with the copper. Rotate the cutter around the pipe, then tighten the knob about a quarter turn. Repeat this process of rotating and tightening until the cutter wheel cuts through the pipe. A tubing cutter ensures a burr-free, perfectly square cut.