Fasteners Workbench in FreeCAD
Allows you to make nuts, bolts, threaded rods of many sizes and types. Threads are accurate and to standards.
Download the archive (.zip) file here:
Extract the contents of the archive to a directory named 'Fasteners' and copy to a new directory named 'Mod' within the '.FreeCAD' directory in your $HOME as follows:
cd /tmp wget http://theseger.com/projects/wp-content/uploads/2015/06/Fasteners_V0.2.15.zip unzip Fasteners_V0.2.15.zip mkdir $HOME/.FreeCAD/Mod mv Fasteners $HOME/.FreeCAD/Mod/