Right Hand Thumb Rule

It is very important for you to know the conventions in AutoCAD before you proceed with 3D.

AutoCAD follow these three conventions :

  1. By default, any drawing you create in AutoCAD will be in the world XY plane.

  2. The right hand thumb rule is followed in AutoCAD to identify X, Y and Z axis directions. This rule states that if you keep the thumb, index finger, and middle finger of the right hand mutually perpendicular to each other, as shown in fig. below 

then the thumb of the right hand will represent the direction of the positive X-axis, the index will represent the direction of the positive Y-axis, and the middle finger of the right hand will represent the direction of the positive Z-axis.

  3. The right hand thumb rule is followed in AutoCAD in determining the direction of rotation or revolution in the 3D space. The right hand thumb rule states that if the thumb of the right hand points in the direction of the axis of rotation, then the direction of the curled fingers will define the positive direction of rotation. See fig. blow :

This rule will be used during the rotation of 3D models or the UCS and also, during the creation of revolved surfaces and revolved solids.