Welcome to the Complex modeling - Cogwheel tutorial.The aim of this tutorial is to teach an initiate/beginner user of 3D Studio Max how to build a simple cogwheel.
Tutorial level : easy
This tutorial was developed using 3D Studio Max 6 , but it will work on most versions of 3D Studio Max if you will find the tools needed for this tutorial.

First of all , some tricks.When you want to model something you have a lot of options in 3D Studio Max.Still , most of the time I use only two objects : the box and the cylinder.And I am able to create very complex models.Most of the cases you will not need anything else.And this is the case here.
Now , let's begin!First of all , in case you haven't already done so , enter 3D Studio Max.
Now go here Create>Geometry>Standard Primitives and select Cylinder.If you don't know where to go , look at the picture number one.
Now expand the Keyboard Entry rollout.What we need is a prametrized cylinder , because we will get along more easy with it.Anyway , you must choose the height to be much smaller than the radius.
Keep in mind this and enter some parameters up to your taste in the Radius and Height fields of the Keyboard Entry rollout you have just expanded.Also , insert in the Height Segments field and in the Cap Segments field 1.Choose more sides and your cogwheel will have more teets.I have choosed 72 sides for the one from this tutorial.
Also , I have choosed a radius of 8.0 and a height of 1.0.After this , press the Create button and your cylinder is ready at the center of the world.Select it if you haven't done so already (after creation , an object is by default selected).Give a right click on it and choose from the menu that will appear Convert to>Convert to Editable Mesh.You can choose also other selections up to your prefferences , but I usually choose for my objects to be editable meshes.See picture two.After this , navigate through the world to have a more clear view of the cylinder.Select from the Selection rollout the Vertex mode.Go to the top view and holding CTRL select half of the pairs of points like this (see picture three).
The red ones are the selected points.Now right click on the cylinder and choose Scale , like this (see picture four).