We pioneered a simple and soft mechanical cutting process for single wall carbon nanotubes involving diamond particles as abrasive material, High resolution transmission electron microscopy observation reveals shortened nanotubes always organised in bundles. Micrograph analysis allows us to determine the breaking mechanism of the bundles. The average nanotube lengths, estimated using AFM images, are ranging from 300 to 700 nm. Adsorption measurements show a topological modification of the material with the presence of new microporosities ranging in the average nanotube diameter.