Spur Gear DP Question

Another potential source for gears could be from the hobby R/C vehicle market.

HobbyKing has a lot of inexpensive gears both plastic and metal, metric and imperial. It may take a bit of searching since they aren‘t sorted by gears.

Search results for: 'gear'

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Maybe a somewhat silly question, but have you considered a worm and pinion as part of the gear train? If your design must overhaul (run backwards) then such would be out of the question. But a consideration nonetheless. I build small model trains (HO) and have cut a few pinions with 0.4 modulus, I don't know what the DP would be, but very small. The worm was cut with a "rack" cutter on the lathe with it in threading mode. Such gears, both worm and spur, are available from many hobby suppliers. RC models, trains, airplanes, and such. Many (most?) will be plastic or phenolic. But metal gears are available. I have bought from "Boston Gear" in the past, but they are scant of smaller sizes.

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An afterthought, if I may. A lot depends on the general size of your device. But you did state that there is not a great deal of torque involved. Many (most?) electric screwdrivers and many battery powered drill motors have a planetary gear mechanism built in. Often thas mechanism has two or more stages putting the desired reduction beyond that desired. But they can be dismantled and individual stages applied. As well as a convenient source of small gears. I have several old metal cased drill motors that have failed motors. At today's prices, they are cheaper to replace than repair. I have salvaged the gears between the motor and chuck. Mostly spur gears, they fit your description of desired tooth count. Give or take. . . Another consideration. . .

Planetary gearing can be applied several different ways resulting in different ratios for the same gears. It is best pursued from a book like Machinery's Handbook, where the many setups are described in detail. In the past, I had "published" a project where such a geartrain was applied to an Asian 9X20 lathe. The original website is down now (after ~15 years) but the article is still floating around a few places. It was built with parts from an automotive automatic transmission and had considerable torque transmission. Being about 5/8 inch thick and around 5 inches diameter, it gave a 3:1 ratio for the "front end" of a lathe that was quite well made but ran too fast for me to learn on.

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