Spiral Gearing - Calculation and Design, Herring-Bone Gearing, Gear Hobbing #224718

The terms spiral gear and helical gear are, in usage, synonymous, the only difference being that the former of these terms is absolutely incorrect. Inasmuch, however, as the word spiral is in such common use among mechanics in this connection, the writer has not had the moral courage to use the more 'proper term throughout this treatise, but it would be a good plan for the readers to become familiar with the term helical as applied to gearing.