Abstract: The invention relates to a manual and portable device for crimping ferrules onto bundles of optical fibres comprising a number of fibres such that these fibres may be hexagonally arranged. The device primarily comprises means for holding the ferrule in the tool, crimping means essentially consisting of an element supporting three knurled rollers which is capable of being rotated whilst the three knurled rollers, at the same time as rotating, may be moved progressively nearer the axis of the bundle until their spacing corresponds to the minimum cross-section of the bundle. The device may also comprise a release mechanism enabling the approach movement of the knurled rollers to be stopped when this cross-section is reached.