Instructables

Easy Pencil Gears - 32 Tooth - Project #1

Picture of Easy Pencil Gears - 32 Tooth - Project #1
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Pencil Gears.jpg
Pencil Gears.jpg
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.
 
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Step 1: Materials and Tools

Picture of Materials and Tools
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Tools:
Dremel or equivelant high RPM cutting tool
Ruler
Two permanent markers of differing colors
Hot Glue Gun
Adhesive Spray
Scissors
Paper printout of attached Visio

Materials:
Box of pencils.  For each 32 tooth spur gear, plan on using about 4 pencils.  I used #2 pencils from the dollar store.
CD/DVD
2 Liter Plastic Bottle Cap


Step 2: Attach CD Template to a CD/DVD

Picture of 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

Picture of Mark Pencils for Cut Marks
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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.
Alderin8 months ago
Cool idea!

Doing two of these gears with the pencil pieces glued on at 45 degrees would also allow for a 90 degree direction change.

It would be good to add a bit about how to calculate the size of smaller or larger gears, as one of the best things gears do is add mechanical advantage through gear ratios.

Great work!
mszymczak (author)  Alderin8 months ago
I really like that idea Alderin. I have family camping trips the next two weekends but will post after those are over.

When I saw your post, I immediately thought how 4 gears at 90 degrees in a primitive slip-differential configuration would be pretty awesome. It would need a fairly rigid/sturdy support structure to keep the axis in alignment. I would only attempt that with a table jig saw. A hand held dremel would be too inaccurate.
Alderin mszymczak8 months ago
The 45 degree cuts on the pencils could be done with a hand held hacksaw with decent accuracy. All of the cuts could be, for that matter, with the possible added bonus of reducing the "coal miner look". :-)

I bought a yellow plastic miter jig at Home Depot for something like $5 that has a 45 degree 'vertical' slot that would allow several pencils to have their 45 degree slots cut at once (with care to keep the blade level for all pencils).

Hope the weather is good for your camping trips!
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