Putting Some Teeth into Gear Knowledge
“W
hat do you need from gears?” is the question posed by the author of SME Tech Paper TP51PUB29 in ex-
plaining that what a purchaser says he wants does not always correspond to what he actually needs. Rather than relying on standardized choices, the author advises tool engineers to keep in mind that “the best gear for any particular application is the cheapest gear that is adequate for the service it is called upon to render,” while meeting conditions of bulk or size, form, position and operation, assembly or functioning. “No two different applications are ever exactly alike. This means for anyone who is closely concerned with the needs of gears, there is never a dull moment.”
Published discussion on the above paper by a General Electric engineer added that a gear designer’s needs may be simple, “but getting what he needs may require him to spend a lot of time investigating gear problems.” Additional com-
mentary from the chief research engineer for the Packard Motor Car Co. discussed that “most engineers have some very definite ideas for surface finish. Our policy has been to ask the gears to tell us the surface finish they desire, as evidenced by the surface condition of the teeth after actual operation at the design loads.” Sometimes that’s what manu- facturing engineering is all about.
Gear Finishing
The quality of a finished gear is affected by the quality of the blank on which the gear teeth are cut. TP86PUB383 de- scribes how good inspection and quality control procedures will result in early detection of bad blanks, which can then be removed from the system before subsequent expensive op- erations are performed on the blank. Stephen P. Radzevich’s paper on finishing precise gears for low-noise car transmis- sions (TP04PUB261) explains that among various methods for finishing gear teeth, shaving is still the most widely used because of short process times and low costs. The predomi-
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