index-wheel

from The Century Dictionary.

• noun An index-plate.
• noun A wheel having graduations and notches on its periphery, used to regulate the advance or feed of a machine.
• noun A wheel with 80 teeth, divided into 20 sections of four teeth each, attached to the combing-cylinder of a cotton-combing machine to facilitate the adjustment of the time for the action of the various parts that act on the cotton.