A pattern had to be made for the differential drive gear for the 1910 Big Four tractor, which was equipped with three speed options. Al chose a low speed to match the original differential gear. To make the pattern, he used medium-density fibreboard in 3/4-inch sheets. He cut the sheets into circles, glued and screwed them together to make a 5-inch part, then used a lathe to true the pattern. A rotary table was used to index the gear for the tooth cutting. This is the finished pattern ready for the foundry.
Photo courtesy Harriet Severson