Here is how a helical gear is modeled in Catia V5r19 using the mechanical part design workbench. This tutorial is exclusively in Catia but similar procedure may be followed in Solidworks also.
STL (Stereolithography, filesize: 466 KB), OTHER (Other, filesize: 15.4 MB), SLDPRT (SolidWorks, filesize: 268 KB)