Design Example: Gears

A reliable way to transmit rotational motion between parallel shafts is to use spur gears. In essence, a pair of gears at the right distance apart with the teeth in mesh will act like rollers in contact. With a single pair of gears, the rotation is reversed. A small gear driving a large gear will reduce speed but increase torque; large driving small increases speed but decreases torque.

The following models are derived from the GPL-licensed Solidworks Gear Generator available on Thingiverse. This clever file uses a design table to generate the involute tooth profile parametrically. The various gear sizes are copies of the the same part file using a different tooth count parameter in the design table.

This set of gears is standardized with a 2 mm module and 20 degree pressure angle, so all gears in the set are compatible. With a 2 mm module, the pitch radius in mm is the same as the tooth count. E.g., a 20 tooth gear driving a 40 tooth gear has pitch radii 20 mm and 40 mm, so the axes should be placed 60 mm apart.

The SolidWorks model files may be found in the gear-demo folder, or may be downloaded as a single file as gear-demo.zip.

Spur Gears

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Laser-cuttable spur gear with 40 teeth and a 2 mm module. The pitch radius is 40 mm, same as the number of teeth. The bore should be customized for your application.

Examples:

Rack Gear

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Laser-cuttable spur rack gear with 27 teeth and a 2 mm module. A rack is useful for converting rotary into linear motion or vice-versa.

Gear Test

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Gear test plate with 10 tooth and 40 tooth spur gears installed. The axes are 50 mm apart.