The inner thread is an ellipse filled with thread turns. The thread turns are represented by ellipse segments. There is also one special point: the thread point.

The thread point marks the end of the thread turns, i.e. it defines the depth of the thread bore. It lies on the short axis passing through the center point. The thread turns are created parallel to the outer ellipse with equidistant spacing.

As with the ellipse, the inner thread represents in part the projection of a circle onto the imaging plane. The circle in this case forms the edge of the threaded bore. As with the ellipse, the ellipse value and orientation angle which are currently set determine the display.