Tube insertion devices are configured to allow a user to manually insert a hollow tube into a receiving bore, e.g., a pen tube into the bore of a blank. In some implementations, the devices include (a) a pair of elongated arms, each arm comprising a gripping portion and an insertion portions, each of the insertion portions terminating in a distal tip, and (b) a connecting portion joining the arms such that the arms pivot about the connecting portion in a plane defined by the arms when the gripping portions are pressed together by a user. Each of the insertion portions preferably includes a relatively wider proximal portion and a relatively narrower distal tube-carrying portion, the change in width between the proximal portion and the distal portion defining a stop surface.