When I look a references to involute gear cutter set they always refer to eight cutter to cover the range of sizes, and normally list them from a #1 being 135 teeth to a rack to #8 being 12-13 teeth. When I look at the gear cutter sets out of China on ebay they number them the other way around (#1 being 12-13 teeth to #8 being 135 teeth to a rack ). What is the convention? Is this an English vs American difference or a Module vs DP difference? Immediate reason is I wanted to cut a 33 and a 34 tooth gear so ordered a #5, but now I'm not sure if what is going to arrive is for 21 to 25 teeth or for 26 to 34 teeth. As a secondary question how important is it to use the correct cutter? Can you get away with using the cutter number above or below in a pinch?