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.

This instructable is awesome but it need's a video. Someone unfamiliar with CAD and Draftsight is going to have no idea how to follow these steps. A screen recording of the process would help people know which icons to click on/commands to enter without having to spend hours learning how to use the draftsight program. (Not that learning DraftSight isn't worthwhile.)

EV Builder (author)  nathanaloysiusbash15 days ago
Thanks for the input, when I get a chance I will have see if I can figure out one of those screen capture programs. If you can tell me what size sprocket do you need.I will make the video showing how to draw that one exactly :)
Cool. The one I want to make is 105 teeth, 17 inches in diameter (not sure if that's actual outer diameter or circular pitch diameter), then it has a hole in the middle 3.4 cm in diameter. It's for a 1 speed crank. It has the same pitch and roller diameter of #40 chain. That would be awesome if you'd find time to do that. I don't know what operating system you have on your computer but I do know that for the last few version of Windows there are screen recorder utilities made by microsoft. What operating system do you have?
EV Builder (author)  nathanaloysiusbash2 days ago

Hey its going to be a while before I can post an update video so in the mean time I added a new page with your sprocket already drawn on it, feel free to request other sizes.

gibbert6 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!