Cutting brake or fuel lines with a hacksaw leaves a jagged, angled edge full of metal shavings. This ruins the flare connection and can send metal debris into the hydraulic system. A tubing cutter makes a perfectly straight, clean cut. You clamp the tool onto the tube, with the pipe resting against two smooth rollers and a sharp, hardened steel cutting wheel pressing against the metal.
You rotate the tool around the pipe, tightening the feed knob slightly with each turn. The wheel scores a deeper groove until the pipe cleanly snaps. Most cutters include a fold-out reamer blade to clean the inner lip of the cut pipe. Always clean out the inner burrs before flaring the tube. This ensures a tight, leak-free seat on the line fitting.