Answer: cut the copper tubing in a miter box with a hacksaw, or use a pipe cutter with a wheel.
You need the right equipment to cut copper tubing properly, whether it is hardened copper or annealed copper. First possibility: a hacksaw associated with a miter box. Take the copper tube you want to cut and place it in the miter box, then cut it gently without forcing with the hacksaw. Second possibility, even simpler and more practical than the first, use a pipe cutter with a wheel. It will suffice to place the copper tube in the rollers of the tube cutter, and to tighten the knob. As with all metals, cutting copper always causes burrs, use a reamer (also called a "trimmer") to remove them. You can buy all of these tools in specialty stores for a small fee. You too, send us your brico question