How to make herringbone gear in autocad

Here is complete video showing each step to model 3d herringbone gear with autocad,
https://www.youtube.com/watch?v=p7nzrRZcR1s
you can find lots more similar tutorials here
http://www.sourcecad.blogspot.com
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Step 1:
This is completed 3d herringbone gear
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Step 2:
this layout is used to make this herringbone gear