Simple Steam The Myfordboy Traction Engine Part 4 Gear Cutting (1)

This time the larger gears are cut using an involute gear cutter. Although I have a rotary table with index plates to do the indexing I thought I would use my spin indexer instead. A rotary table and index plates will give a large number of divisions but it's easy to miscount the number of turns and holes required. Don't ask how i know! The spin indexer has 36 holes and will give 360 divisions by using the vernier holes. My gear has 72 teeth so 36 full holes plus 36 holes with the index pin in the number 5 position. Next time pinions are cut with 14 divisions. 14 does not divide into 360! If I make more castings for this engine I will also be able to supply ready cut gears.