A "'left hand "'spiral bevel gear is one in which the outer half of a tooth is inclined in the counterclockwise direction from the axial plane through the midpoint of the tooth as viewed by an observer looking at the face of the gear.
12.
Fellows moved to Springfield in 1889, working first at a screw-making machine before being transferred to the drafting department at J & L . In this capacity he became interested in the problem of manufacturing gears, which requires accurate shaping according to mathematical principles in many different forms, including spur gears, worm gears, helical gears and spiral bevel gears.
