The board shows the demonstration of this phenomenon of Interference and Undercutting.
When we rotate the teeth in anticlockwise direction, as the teeth is undercut is gives us a smooth working.
When we give a rotation in clockwise direction, we can observe that the
rack tip will be resisted by the tooth flank thus giving interference
Interference and Undercutting Operation Manual, Lab Instructor Guide and Student Workbook. Interference and Undercutting for Educational Vocational, Didactic Technical Training Equipment Labs.