How to Draw a Sprocket Gear

Picture of How to Draw a Sprocket Gear
When it comes to power transmission in DYI project sprocket gears, sometimes called chain gears, offer several advantages over other types of methods of power transmission such as belts/pulleys and meshing gears.

      1. Unlike belts they can transmits large amounts of torque
      2. Unlike meshing gears they don't need to be constantly lubricated
      3. Unlike belts and mesh-gears the spacing between centers can be easily adjusted by shortening/lengthening the chain

Despite these advantages, few people know how to draw sprocket gears, which are designed based on pitch rather than mesh.

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Step 1: Get DraftSight or other 2D CAD

Picture of Get DraftSight or other 2D CAD
The first thing you will need is a drafting program to draw the sprocket gear with. I recommend DraftSight, which is the free CAD program I used for this demo.

For those who learned how to use, and are hopelessly addicted to AutoCAD's GUI, I might note that DraftSight has the look and feel of classic AutoCAD without the $4000+ price tag.

Step 2: Determine your Key Dimensions

Picture of Determine your Key Dimensions
Next step is to determine the Pitch and Roller Diameter for your chain size. Also you need to determine how many teeth the sprocket needs to have.

I will be demoing 40 tooth #40 chain, which has a Pitch of .5in and a roller diameter of .313in.
gibbert3 months ago

Thanks for putting this up. I've been looking for this for a while. I might be able to make my own chainring now!