Faithful followers of this blog can complete that mantra without prompting, but for new readers — the beginning of wisdom is calling things by their proper name. The first thing we teach children is what things are called. Languages vary around the world but caregivers devote countless hours and display incredible patience to ensure that the little one can say “cat” when they see one. It is perfectly fine that “cat” has a unique word in a given language, yet we all know that one country’s “cat” is essentially the same as another’s.
Mathematics is said to transcend language. Gears involve a great deal of math, so moving from one country to another should, theoretically, be relatively painless. If only this were so. De-cyphering a technical paper written in another country (and language) can be a minefield far more complex than just converting millimeters to inches and Newtons to pound-inches. Besides the measurement units there are significant differences in our understanding of how stresses are combined or applied.
Local nomenclature further complicates any attempt at a “universal translator” for gear terminology. A well-intentioned effort to explain a common gear geometry modification as “long and short addendum” has resulted in generations of American engineers wondering if pinions and gears have different whole depths. Our European friends talk about X factors and we need reminders that they are essentially the same thing.
So, our teaching of gears for novices needs to begin with a consistent nomenclature chart — preferably one with easy-to-follow diagrams of where on the gear that term comes into play. Almost every machine shop in this country has a few copies of Machinery’s Handbook (Available on Amazon; new hardcover $71.84; can be rented for $31.50). Since it was first published in 1914, this little book has provided basic — yet essential — gear information. Although aimed at the operator, some surprisingly detailed gear information is included, starting with drawings showing the names of gear features. If you have nothing else to reference during our lessons, keep your copy handy.