It was a typo when I wrote "vert thin bodies." It was meant to be "very thin bodies." The body thickness is something for you to determine. There should be some real gear thickness. Or are you trying to analyze in 2D? For that, don't make solids in SpaceClaim. Just make the surfaces in the XY plane, and set probably "plane stress" on the surface bodies if the gears are meant to be thin relative to the other directions.
Your remaining problems are all mesh sizing issues, and you really need more training with using the meshing in Mechanical. The geometry is Ok since it is able to generate a mesh, albeit too fine in your first case. For the adaptive sizing set that "Element size" near the top to a value. It is set to "default" in the first picture. Set it to the size you want most common throughout the bodies, at least a lot larger than the element size you see on the tooth. Your last picture show the affect, although 50.0 m is obviously too large. Maybe 0.4m would be more accurate. You can set a smaller local "edge size" on the edges around the circumference where the teeth are.
You are navigating away from the AIS Discovery experience