This is a wicked fast way to create spur gears using pencils. Making gears can be frustrating for many people. This method creates reliable gears that do not bind. It takes advantage of the hexagonal profile of a pencil to create a forgiving pitch and pressure line.
These gears are suitable for learning the basics of gears. It is not intended to be a high precision or strength substitute. It is, however, a great way to slap together simple prototypes, build a spirograph, hobo clock, or crane.
Step 1: Materials and Tools
Dremel or equivelant high RPM cutting tool
Two permanent markers of differing colors
Hot Glue Gun
Paper printout of attached Visio
Box of pencils. For each 32 tooth spur gear, plan on using about 4 pencils. I used #2 pencils from the dollar store.
2 Liter Plastic Bottle Cap
Step 2: Attach CD Template to a CD/DVD
Print the attached Visio template. If you don't have Visio, install a Free Visio reader. This template is for a 32 tooth gear.
Cut the circle out.
Spray the back of the circle with adhesive spray.
Attach template to the CD/DVD.
Step 3: Mark Pencils for Cut Marks
Pencils are awesome. Did I mention pencils are awesome. The hexagonal profile of the #2 pencil gracefully allows them to interlock with one another. Let's leverage that virtue to our advantage to make gear teeth.
For each pencil, you will need to mark the CD/DVD groove location and the tooth full cut line.
Color #1 (Black):
Line the pencil along the ruler and place a mark every 1/2 US Inch.
Mark the edge of the pencil (lead profile side) so that it indicates which side was just marked.
Rotate the pencil 180 degrees so that the previously marked side is lying facing down. Verify with your edge mark.
Color #2 (Purple):
Offset the pencil on the ruler 1/4 US Inch and place a mark every 1/2 US Inch. This will be the groove location.
Step 4: Cut the Pencils
This is very loud and messy. Ideally, do all of your cutting outside with a fan blowing the debris gently away from your face. If you don't, you will end up looking like a coal miner.
Always wear good eye protection. The high RPM cutter can easily tear and throw debris or the cutting disc into your face. If you don't, you could easily end up losing an eye.
Begin by cutting the groove marks (Purple). You'll need to bite into the pencil about 1/4 of the way toward center. I also like to paw backwards with the cutting disc to widen the width of the groove.
After all of the grooves have been created, sheer off each individual tooth by using the (Black) mark on the opposite side of the pencil.
Your gear teeth are going to be very dusty. You may want to wipe them off with a wet paper towel to remove the dust.
Step 5: Attach the Teeth
Begin by hot gluing the gear teeth to the dark line indicated on the template. Line up the pencil lead with the line. That will get your roughly into position.
After all 16 main gear teeth are in position, go back around and add the other 16 teeth in between the original 16. You should be able to eye ball center.
Remember, these gears are very forgiving. You don't need to be very precise with their placement.
Step 6: Attach Bottle Cap
Place a healthy amount of Hot Glue on the top of the Bottle Cap. Press the Bottle Cap onto the backside of the CD/DVD (opposite of the template). Use the CD as way to determine center. This does not need to be precise. You will drill a hole from the template side using the line intersection points in order to determine exact center for your particular application.
That's It! You have a gear. Now repeat for as many gears as necessary for your project.