Hi. Only a single responses to a review is permitted - for further help please open a ticket at: https://projects.blender.org/extensions/add_mesh_BoltFactory/issues
Your review is showing against v0.5.0, the latest version is v0.7.1; if possible please update by going to Edit->Preferences->Get Extensions and finding BoltFactory and pressing the update button.
Why is the bolt small? Most likely you are working with a project scale of meters. A default bolt is about 10mm large. You can zoom in or use the dot (.) on the numpad to focus on the bolt immediately after placement.
holaa necesito ayuda instale el complemento como debe ser y cuando pongo un tornillo no aparece fisicamente el sistema lo toma como si existiera pero no se ve aun teniendo la visualizacion activada necesito su ayuda