Giant #2 Pencil (that Writes!)

I decided to make a really big pencil. I wish I had a fantastic reason for making it, but really it just sounded like a fun idea at the time. To be fair, I had been wanting to make a typically small object overly large on my rotary for a while.

Tools:

Cnc router - 3 and 4 axis

Drill

1.25" forstner bit

1/8" drill bit

Saw (hand or bandsaw)

Bench vice

Software:

Fusion360 with machining extension (or similar that supports 3/4 axis rotary)

Supplies:

4"x4"x28" board (standard construction lumber)

3"x1.5"x.10" walnut board

1.5"x1.5"x6" walnut board

10.5"x6"x.75" (2 pcs) any hardwood

8"x8"x.5" plywood (with a couple spares)

6"x11" 22ga aluminum sheet

3.5"x3.5"x3" block of pink insulation foam (can be several layers of thinner foam combined if needed)

1/8" graphite (I used the lead for my Pica shop pencil)

Yellow spray paint

Clear coat spray paint

Pink paint (non-aerosol)

Wood glue

16 small wood screws

1" painters tape

In Fusion360 I needed to model each of the pencil parts. First I made the unsharpened wooden pencil. Then I added components for the metal band, eraser, lead (new and sharpened), the 2 inlay, and the sharpened point.

I mounted the 28" 4x4 into the rotary cnc, and carved it into the "hex with rounded corners" shape.

When it was done, I took it off and painted it yellow.

Using the rotary, I took a scrap of walnut and carved a 1.25" cylinder about 4" long.

I drilled a hole 3" into the end of the pencil with a 1.25" forstner bit, then added wood glue and pounded the walnut all the way in. The extra was trimmed with the bandsaw (hand saw would work) and sanded flush.

On the 3-axis cnc, I carved out the four pieces of .1" walnut for the inlay.

Next I strapped the pencil on the cnc and carved the matching pockets near the top. A little glue and a few light taps, and I now have a #2 pencil.

I feel like this detail is very important, as I grew up using yellow #2 pencils because they were required for all our standardized tests.

Now that I have the wood part of the pencil done, I need to form the metal ring from the 6"x11" 22ga aluminum sheet.

I designed a set of form rollers. The positive roller was just a solid version of the ring I had already modeled, and the negative roller was the same outline inverted. I added gear teeth on the end because I needed to keep them in sync.

I carved out the two rollers and locked them together in a tight frame.

Unfortunately I couldn't get enough pressure to get this gauge of aluminum to form with this setup. I wasn't sure where to source a thinner piece locally, and I was worried that anything thinner would dent or crumple if it was ever bumped too hard.

Good thing I had a plan B!

Plan B was to make the molds flat instead of rollers, so I could apply more pressure.

I modeled the pair, then I carved them from scrap hardwood on the 3-axis cnc.

I tried squeezing them with f-clamps, but it still wasn't enough pressure. However when I put it into the vice and really cranked on it with a breaker bar it finally formed! I was happy I didn't have to resort to driving my suv over it, although that would have made great content.

I used one of the form rollers to roll it into a cylinder, and screwed both ends into the pencil.

I wanted this pencil to be functional. I did a quick search, but didn't find pieces of real eraser that would be big enough or in the budget that week. So I went with Plan B, which was pink insulation foam.

I glued together 3 chunks of 1" foam to make a 3.5"x3.5"x3" block. While that sounds easy, I'll point out that spray glue and ca glue melt foam on contact. Normal wood glue worked great. After some quick work on the cnc, I had a pink foam eraser.

I had thought the foam was already eraser colored, but after carving it was fairly dull looking so I decided to paint it. Also good to know, spray paint also melts this type of foam, so acrylics with a brush was the right choice.

The eraser is just pushed about 1/2" into the metal ring. It's a snug fit, so I didn't bother with glue.

What use is an unsharpened pencil? The basic process here was to remove the metal ring and eraser, then chuck it back on the rotary. Run a few paths to rough down the tip, and a final pass with a 1/8" ballnose bit to finish it smooth.

However, there was a minor issue. When I had used the rotary to carve the 24" flat tipped pencil, the right end was supported by the tailstock. To sharpen it to a fine point, the tailstock would be in the way. My solution was to cnc-carve a plywood circle with the rounded-hex cut from the center. The hex hole was just slightly larger than the pencil, and the outer circle had a radius matching the distance from my tailstock to the bottom rails. When this ring was placed over the pencil, the right side was supported at the proper height to be carved. I used 1" masking tape to protect the paint and to make the outer edge rotate smoother leaning on it. I intentionally chose a toolpath that carved left and right so that it kept the pressure straight down and only rotated a few degrees at a time. A circular toolpath would have pushed the pencil forward or back, which were unsupported directions.

I wanted to be able to write and draw with the pencil, so I invented magic writing walnut! Just kidding, I stuck a piece of pencil graphite in the tip. First I used a sanding block to flatten the tip until it was 1/8" across. Then I used a 1/8" drill bit to make a hole 1/2" deep.

I own a Pica workshop mechanical pencil that uses a really thick lead. It's great for drawing lines on wood, and the lead was exactly what I needed. I sharpened the graphite tip and broke off about 3/4", then just jammed it into the hole. It was a good pressure fit and I could pull it back out with my fingers... until I drew a picture with it which pushed it in harder. If it ever breaks off, the rest will probably need to be drilled out to replace it.