Imagine for a moment that your boss invented the herringbone tooth form and tasked you with building machines to cut them. This was the situation Percy C. Day found himself in when he arrived in Milwaukee in 1913. Others were making them using shaping technology, so this well-understood machining method was leveraged with two horizontal-acting shapers timed together so the pinion-shaped cutters converged on the apex and clipped off the shaved chips at a common point. This became the typical machine design.