You can usually cut thin metal rods or tubes with a Dremel rotary tool such as the Model 3000. However, it may not be the best tool for an 8mm thick steel pipe as it could require a lot of force and time. Dremel offers special cutting discs like the SC456 that are suitable for cutting metal, but even these might not be optimal for thicker pipes. For solid steel pipes of this thickness, a more powerful tool such as a metal cutting saw or an angle grinder with a suitable cutting disc would be more suitable.