Introduction: Let's B-sharp: a Musical Modified Pencil Sharpener

About: I am a Christian, an Engineer, and I may be a little crazy (but only a little).

The inspiration for this project came from an unlikely source, a Greek class. Before my Calculus III course meets, a Greek class is in the classroom. Since we can't go in the classroom, my friends and I sit in the hallway and study, which means we tend to get to know what people do on their way to class. One behavior we have observed is that a student from the Greek class always stops at the wall-mounted pencil sharpener outside the classroom and cranks it several times before going into class. He does the same thing on his way out of the class. After observing this several times I got the idea to play a little trick on him. I decided to cause something to happen when he turned the crank. Hence, this project.


-Pencil Sharpener -

I attempted to find one that was as close as possible to the original so that people wouldn't immediately notice the difference.

-Music Box -

I wanted a music box that could fit inside the sharpener and this one had the proper dimensions. As long as the dimensions are the same, any other music box should work.

-Super glue - I used E6000 craft adhesive, but anything that can bond plastic securely to metal should be fine. (I also recommend Loctite

-You will need access to a 3D printer

-You'll also want a metal cutting tool and maybe a vice, file, and some q-tips or thin wire.

Step 1: Disassemble Sharpener

The first thing you need to do is to disassemble the pencil sharpener, pretty much all the way.

Begin by taking the shavings case off the body of the sharpener. Set it aside. Then take a screwdriver and unscrew the screw that holds the handle to the sharpening mechanism. This will allow you to take the sharpening mechanism out. Once you've got it out, put it in your "use this for something at a later date" box. (You do have one, don't you?)

After doing that, take one end off of the shavings case. I took off the more complex end since it was easier. All that is required is a bit of pressure on the wall near the hooks.

At the end of all this, you should have an array of pieces that look like the ones in the picture above.

Step 2: 3D Printing

I had the most trouble with this step. I had to redesign and print out several parts several times before I finally managed to get the dimensions correct.

The Driveshaft and the Inner Aligner are designed to have a print tolerance of 0.5mm on each. This should be enough to allow free movement, but if you find it's not enough write me a comment and I'll adjust the files.

These parts are designed to fit with the sharpener I have listed in the parts list, but I imagine that they would work with similar models.

One thing about the holes in the driveshaft. There are a bit smaller than they needed to be, but a drill bit will fix that issue. I'm leaving them the size they are in case you find a music box with a smaller diameter ratchet lever (the fancy name for the thing you turn).

One of the photos above shows a part that I ended up not using. I had designed it to keep pencils from being stuck inside after assembly and destroying stuff, but I found that
1. It's not needed

2. It didn't fit right anyway.

Step 3: Prepare Music Box

Basically, the only thing that needs done to the music box before assembly is cutting off part of the ratchet lever (the thing that you turn with your hands). This can be done with a hacksaw, Dremel, or file. I used a hacksaw blade and held the music box in place with a vice. If you're careful, you can do this without a vice.

After I cut off the unneeded piece, I used a file to smooth out the sharp stuff. It's probably not necessary, but I did it anyway.

Step 4: Inner Assembly

The inner assembly is very simple. Just make sure the inner frame thing is oriented correctly before you reassemble the shavings case. (I speak from experience. I had to unassemble and reassemble the thing three times before I got it right) You want the ratchet lever to stick out of the center of the circle in the shavings case.

After the music box is in position, you can close up the shavings case again.

The inner aligner is placed in the way shown in the picture. It doesn't need glued.

Step 5: Outer Assembly and Finishing Up

Use a drill bit to get the holes in the driveshaft to the appropriate diameters. It shouldn't need too much change, so be careful not to take out too much material.

After getting the holes to size, attach the handle to the driveshaft using the screw and then stick it in the base (see pictures).

Then get a little glob of E6000 adhesive and stick it on the hole that the music box attaches to. You can use a q-tip or wire to get it down in the hole. Don't use too much or it'll work its way into the music box and gum up the movement (I once again speak from experience).

You won't be able to easily unassemble this after the glue has set, so make sure you've got everything in the right place before you

Set it aside and let the glue dry for about 48-72 hours.

Step 6: Attach to a Wall and Wait

After the glue has dried, attach it to a wall where there was/is a pencil sharpener and wait for someone to come spin it.

What happened when I did it:

I got to the hallway early, but I decided I didn't have enough time to mount it to the wall before the guy showed up. So I waited until after he had gotten there, spun the sharpener, gone to class and the class had started before I swapped the two. I just used one screw since that was enough to hold it in place (though if this were a permanent fixture, I'd use three). After I got it mounted to the wall, I sat outside the classroom and waited for him to come out again. When he did, he went to the sharpener and spun it a few times, realized it was making music, and then kept spinning it for a little longer. Then he asked, "who did something to this?!" before leaving for his next class.

I thought it was a pretty great conclusion to the project.


Thank you for reading. This project wasn't as difficult as the ones in my previous two Instructables, but it was still fun to work on.

This is an entry in the Modify it Speed Challenge. Your vote is appreciated. Thanks.

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