Tutorial - Making a herring bone gear in AutoCAD?

Here is the tutorial.
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Step 1:
I will use the body created in previous tutorial on Creating helical gear in AutoCAD.
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Step 2:
Enter MIRROR3D command.
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Step 3:
Select the gear body to mirror and press enter. Now it asks for 3 points of the mirror plane.
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Step 4:
We will select the three vertex of the gear body of the top plane. First one is like this.
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Step 5:
Now we have the body mirrored.
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Step 6:
Enter union command.
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Step 7:
Select both bodies and press enter. Now we have herring bone gear created in AutoCAD.
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Step 8:
Subtract a cylinder from the gear body and we have the required gear.